By B. Hernando. Troy State University - Dothan. 2019.

The antidia­ tissues betogenic functions of insulin are mediated by its action on liver kamagra effervescent 100mg without prescription, adipose tissue and muscle purchase kamagra effervescent with american express. Once insulin action is over cheap kamagra effervescent 100 mg otc, again they are internalized In general, insulin increases glucose entry into cells into the vesicles. Glucose Transporters In Liver Glucose enters the cell by means of facilitated diffusion or In liver, insulin promotes glucose storage and prevents its by secondary active transport with sodium in intestine and production by following mechanisms (Flowchart 60. Insulin facilitates glucose entry into the hepatic cell by other tissues, entry of glucose into the cell is facilitated by inducing the action of the enzyme glucokinase. Thus, by facilitating glucose entry into the tated diffusion of glucose into the cell: cells and also simultaneously converting glucose into 1. Therefore, facilitated that mediate secondary active transport of glucose in diffusion of glucose into the cell continues. Insulin also facilitates the use of In Adipose Tissue ketoacids by peripheral tissues. Glucose is also stored as muscle glycogen, which is phate in adipose tissue, which is also induced by stimulated by insulin. On Fat Metabolism In Liver Actions of insulin on fat metabolism are as profound as its Insulin is anti-ketogenic and lipogenic in liver: influences on carbohydrate metabolism. The anti­ketogenic function of insulin is achieved by storage of fat and inhibits mobilization and oxidation of its stimulation of malonyl-CoA formation. It decreases the level of free acetyl­CoA is converted to malonyl­CoA by the enzyme fatty acids and ketoacids in the plasma. The functions of of acetyl­CoA carboxylase and thus increases malonyl­ insulin on fat metabolism are achieved by its actions on CoA formation. It facilitates protein syn- thesis in the muscles and liver by following mechanisms: 1. This is achieved by induction of gene transcription for various proteins by insulin (Fig. Thus, it decreases release of amino acid from conversion of acetyl-CoA to malonyl-CoA by the muscle and inhibits their oxidation. Insulin is considered as a physiological regulator of + enzyme glucose-6-phosphate dehydrogenase. This action is partly + plasma K level; and therefore is very useful in the mediated by its inhibitory effect on neuropeptide Y management of acute renal failure (Clinical Box 60. Chronic insulin excess increases body weight and adi- lin sometimes develop hypokalemia. Insulin stimulates transcrip- hypokalemic effect may be prescribed in the treatment of hyperkalemia as seen in acute renal failure, for prompt relief. Thus, insulin facilitates growth of the individual, in addition to its stimulation of protein synthesis. There­ Other Actions of Insulin fore, deficiency of insulin in childhood (as in diabetic 1. Insulin increases entry of phosphate and magnesium children) decreases their height, growth, and matura­ into the cell. It also increases reabsorption of K , Na , and phos­ In summary, insulin by acting on liver, adipose tissue phate from the kidney. Diabetes mellitus is the most common endocrine disorder in both developing and developed worlds. Note, insulin promotes transfer of amino acids into the cells and increases pro- food (increased calorie intake), junk foods, sedentary life, tein synthesis. Star indicates site of environmental factors and stressful life are among the action of insulin. Other specific types of diabetes patient is usually treated without insulin replacement 1. Genetics defects of insulin action However, recently it has been observed that more 3. Etiological classification of diabetes is depicted in (glucagonoma), etc Table 60. Many patients demon­ pancreatic diabetes following pancreatectomy in strate antibodies against b-cell surface antigens. For his exceptional contribution to diabetes research, the European Association for the Study of 2. If one of the twins develops the disease the other Diabetes has, since 1966, in his name is awarding Oscar Minkowski twin has more chance of developing the disease than outstanding contributions to the advancement of (1858–1931) people in the general population (the concordance knowledge in the field of diabetes mellitus. Sometimes it occurs due to mutation of proinsulin of b cells of pancreas or due to decreased sensitivity of gene that decreases insulin synthesis. In animal models, diabetes is produced experimentally by administration of alloxan or Type-2 Diabetes Mellitus streptozotocin (experimental diabetes). This is usually caused by untreated diabetes, plasma glucose concentration is insulin receptor resistance. The chance of identical twin developing the disease cose though they are surrounded by a high concentration (concordance rate) is 100%. The disease usually starts late, in third or fourth decade vation in the midst of plenty”. The patients are usually overweight and sedentary in chemicals (insulin like substances) in the body having their habit. Age of onset Before the age of 40 (Juvenile onset diabetes) After the age of 40 (Maturity onset diabetes) 2. Usual complication Ketoacidotic coma Hyperosmolal coma Mechanism of insulin resistance: the exact mecha­ 4. Obesity: In obesity, insulin fails to transport glucose Secondary Diabetes Mellitus into the tissues. Obesity eventually leads to hyper­ Diabetes also occurs due to the diseases of pancreas like insulinemia, hyperlipidemia and accelerated athero­ pancreatitis, or following pancreatectomy. Diabetes can also sclerosis that are part of metabolic syndrome (Clinical occur in Cushing’s syndrome (cortisol increases plasma glu­ Box 60. These are combinely called as metabolic cose) and acromegaly (growth hormone increases plasma syndrome of obesity. These forms of diabetes are included under the insulin resistance and dyslipidemia decrease. Adipokines: the chemical signals originating from adi­ titutes about 5% of the total diabetes. The mortality rate is high in metabolic Diabetes mellitus is characterized by polyphagia, polyuria, syndrome. Insulin also facili­ tates utilization of ketone bodies (acetoacetate, acetone, and b­hydroxybutyrate) by the tissue.

They are usually available for Following the administration of an antigen (immunogen) to a interaction with an antibody only following denaturation of host animal buy generic kamagra effervescent 100mg, antibody synthesis and/or cell-mediated immu- a protein and are not customarily in the native confguration buy genuine kamagra effervescent on-line. To be immuno- Antigenic determinants or epitopes are sometimes called genic buy kamagra effervescent with american express, a substance usually needs to be foreign, although some immunodominant groups. They should usually have a molecular weight of at least 10,000 kDa and be either In contrast to the natural antigens that constitute part of a proteins or polysaccharides. Nevertheless, immunogenic- microbe, one derived exclusively by laboratory synthesis and ity depends upon the genetic capacity of the host to respond not obtained from living cells is termed a synthetic antigen rather than merely depending upon the antigenic properties (Figure 3. Side chains of differentamino acids are attached directly to the the specifc parts of antigen molecules that elicit immune backbone and then elongated with a homopolymer or, con- reactivity are known as antigenic determinants or epitopes. Side chains have Even the earliest investigators in immunology recognized that contributed much to our knowledge of epitope structure and small molecular weight substances such as simple chemicals function. Side chains have well-defned specifcities deter- could react with the products of an immune response but were mined by the particular arrangement, number, and nature of not themselves immunogenic. The size of the molecule is less animal but is capable of reacting in vitro with an antibody critical with synthetic antigens than with natural antigens. However, a hapten may be covalently linked Thus, molecules as small as those of p-azobenzenearsonate to a carrier macromolecule such as a foreign protein that ren- coupled to three l-lysine residues (mol wt 750 kDa) or even ders it immunogenic, and can form new antigenic determi- of p-azobenzenearsonate-N-acetyl-l-tyrosine (mol wt 451 nants. Specifc antibodies are markedly which permit them to autocouple with a substance such as a stereospecifc, and there is no crossreaction between them, tissue protein. The excellent ft between An antigen molecule has two or more epitopes (or anti- epitope and paratope is based on their three-dimensional genic determinants) per molecule. Since that time, many studies have been conducted defning the nature of T cell and B cell tolerance. T cells are rendered tolerant with lower doses of antigen and Epitopes that stimulate a greater antibody response than oth- for longer periods of time than are B cells. Tolerance is the principal chemical features of antigens include their a type of antigen-induced specifc immunosuppression and large size, complexity, and ability to be degraded by antigen must remain in contact with immunocompetent cells enzymes within phagocytes. Exceptions include such favored by the route of administration and the physical nature substances as insulin with 5700 kDa. For example, the intravenous route more easily demonstrated with molecules of greater molecu- of injection of solubilized antigen favors tolerance induction. However, size alone does not make the molecule By contrast, the injection of antigen in particulate form into antigenic. It must have a certain amount of internal struc- the skin favors the development of immunity. Linear polymers of polylysine comprised of induces tolerance is often referred to as a tolerogen. The majority of protein antigens contain 20 different amino acids in an To mount an immune response to an antigen, a host must assorted arrangement. The anti- proven in animal studies in which inbred strain-2 guinea pigs gen must also be degradable by phagocytes to be antigenic. Antigen processing includes enzymatic digestion to prepare Lymphocyte proteins in man encoded by Ir genes include the soluble macromolecular antigen. This enables rec- not antigenic even though they might otherwise possess the ognition among B cells, T cells, and macrophages. During development, the body becomes tolerant of stimulate a full complement of immunoglobulins with all fve self-antigens as well as foreign antigens that may have been classes represented, elicit an anamnestic or memory response, artifcially introduced into the host prior to development of and are present in most pathogenic microorganisms. The latter situation describes the induc- ensures that an effective immune response can be generated in tion of actively acquired immunologic tolerance, which a host infected with these pathogens. They inoculated fetal or that elicit only an IgM response and fail to stimulate an anam- newborn mice with cells of a different mouse strain prior to nestic response compared with T cell dependent antigens. Antigens and Immunogens 163 A homopolymer is a molecule comprised of repeating units may activate many T cells, resulting in the release of large of only one amino acid. An antigen is a substance that reacts with the products of an immune response stimulated by a specifc immunogen, Abrin is a powerful toxin and lectin used in immunological including both antibodies and/or T lymphocyte receptors. It is extracted from is presently considered to be one of many kinds of substances the seeds of the jequirity plant and causes agglutination of with which an antibody molecule or T cell receptor may erythrocytes. These include sugars, lipids, intermediary metabolites, autocoids, hormones, complex carbohydrates, phospholipids, An alloantigen is an antigen present in some members or nucleic acids, and proteins. Alloantigens include tion of antigen is a substance that may stimulate B- and/or T blood group substances on erythrocytes and histocompat- cell limbs of the immune response and react with the products ibility antigens present in grafted tissues that stimulate an of that response, including immunoglobulin antibodies and/or alloimmune response in the recipient not possessing them, as specifc receptors on T cells. Two animals of a given the traditional defnition of antigen more correctly refers to species are said to be allogeneic with respect to each other. A complete antigen is one that both induces Alloantigens are commonly products of polymorphic genes. Following the administration of an antigen (immunogen) to a host animal, A cognate antigen is an epitope recognized to be identi- antibody synthesis and/or cell-mediated immunity or immu- fed by a specifc lymphocyte antigen receptor because it was nologic tolerance may result. They should usually have a mol wt of A soluble antigen is an antigen solubilized in an aqueous at least 1000 kDa and be either proteins or polysaccharides. Nevertheless, immunogenicity depends also upon the genetic capacity of the host to respond to, rather than merely upon the An exogenous antigen is an epitope that occurs outside the antigenic properties of, an injected immunogen. Thus, they stimulate multiple from the Indian licorice seed, Gerukia, and (3) zootoxins— T cells that augment a protective T and B cell antibody snake, spider, scorpion, bee, and wasp venoms. This enhanced responsiveness to antigens such as toxins produced by staphylococci and streptococci is an Supratypic antigen is an inclusive term to describe an anti- important protective mechanism in the infected individual. Bw4 164 Atlas of Immunology, Third Edition and Bw6 are classic examples of supertypic antigens. This End-binders are selected anticarbohydrate specifc antibod- implies that an antibody that detects Bw4 will also react with ies that bind the ends of oligosaccharide antigens, in contrast all antigens associated with Bw4, and an antibody that detects to those that bind the sides of these molecules. A pneumococcal polysaccharide is a polysaccharide found Supratypic antigen: See public antigen. Serotypes of this Venom is a poisonous or toxic substance produced by microorganism are based upon different specifcities in the selected species such as snakes, arthropods, and bees. The capsular polysaccharide which is comprised of oligosaccha- poison is transmitted to the recipient through a bite or sting. A capsular polysaccharide is a constituent of the protective coating around a number of bacteria such as the pneumococ- T-dependent antigen: See thymus-dependent antigen. In addition to the pneumococcus, other changes in liver cell components as a consequence of expo- microorganisms such as Streptococci and certain Bacillus sure to the anesthetic halothane. It was used extensively by Michael Heidelberger and associates in perfecting the quantitative precipitation T-independent antigen: See thymus-independent antigen. Biochemical sequestration refers to antigenic determinants A cross-reacting antigen is an antigen that interacts with an hidden in a molecule which may be unable to act as immu- antibody synthesized following immunogenic challenge with nogens or to react with antibody. Epitopes shared between these two anti- molecule may render them identifable and capable of serving gens or epitopes with a similar stereochemical confguration as immunogens. Tetanus toxoid consists of formaldehyde-detoxifed tox- Carbohydrate antigens: the best known carbohydrate ins of Clostridium tetani. It is an immunizing preparation antigen is the specifcsoluble substance of the capsule to protect against tetanus. Individuals with increased likeli- of Streptococcus pneumoniae which is immunogenic in hood of developing tetanus as a result of a deep, penetrating humans.

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These defects also make the cells rigid so that the cells are destroyed prematurely proven 100 mg kamagra effervescent. It also helps to maintain a slippery exterior purchase discount kamagra effervescent on line, so that the Deformability of Red Cells red cells do not stick to the vascular endothelium purchase kamagra effervescent master card. An important determinant of red cell survival is its deform- Integral Proteins ability. Deformability is ascribable to the intrinsic deform- Integral proteins are embedded in the lipid bilayer. When red cells become important membrane proteins are band-3 protein (anion rigid, the viscosity of blood increases and cells are lysed exchanger-1), the glycophorins, Rh D protein and various while passing through the splenic pulp. These proteins allow red cells to participate in wide cell rather than stiffening of their membrane. Band-3 is the major anion-exchanger (chloride-bicar- Red cells have no nuclei, mitochondria and ribosomes. Glycophorin-C provides stability and shape tated diffusion, which is independent of insulin action. Also, when red cells become older, the membrane Red cells metabolize glucose, usually by anaerobic glycoly- becomes rigid. It assesses the integrity of the enzyme in the red cell, glucose-6-phosphate dehydro- red cell membrane. This test detects whether or not the reduced state, which is a strong reducing agent and red cells can easily be hemolyzed. In an isotonic solution, the solution of equal concen- tration as that of red cell content, the red cells remain Clinical Box 11. When suspended in hypertonic solution, a solution malarial drugs, though these individuals are generally malaria resistant. Red cells absorb water by endosmosis, when kept in hypotonic solutions, a solution with less tonicity 1. Hemoglobins also participate in carbon dioxide trans- is increased, the osmotic fragility is said to be increased, port from tissues to lungs and maintenance of acid and when the rate of hemolysis is decreased, the osmotic base balance. Antigen on red cell membrane helps in blood group Shape of red cell determine hemolysis: Increased osmotic fragility classification. The tendency of the cells to hemolyze is called fragility Normal Value and Variations of the cells. Mechanical Fragility Conditions of Diminished Fragility Lysis of red cells due to mechanical stress and strain is • Iron deficiency anemia called mechanical fragility. Red cell diameter is slightly • Thalassemia less than the diameter of average capillaries. Therefore, • Sickle cell anemia when red cells pass through capillaries and splenic pulp, • Obstructive jaundice their membrane undergoes mechanical stress: • Post-splenectomy 88 Section 2: Blood and Immunity Fig. When blood is centrifuged in a tube the red cells are Other factors also contribute. The hematocrit Shape and Number of Red Cells is a macroscopic observation by which the percentage vol- Shape of red cells: the most important factor determining ume of the packed red blood cells is measured. The alteration of shape of erythrocyte decreases rou- provides useful information about the red cell mass leaux formation. The larger the cell count and increases in conditions of increased red cell size of rouleaux, the faster is the fall. Increase or sickle cell disease, more plasma is trapped between the in red cell size without change in their shape increases the packed cells, which gives a false high result. Erythrocyte Sedimentation Rate Plasma Factors the size and number of rouleaux mainly depends on the Red cells have the property of rouleaux (piling one on the fibrinogen concentration of plasma. The piled red cells are heavier plasma also contributes: than the individual red cells. In normal blood, red cells remain separate as they is allowed to settle, sedimentation of erythrocytes is facili- have negatively charged surface that tend to repel one tated due to the presence of rouleaux. When fibrinogen concentration increases Chapter 11: Red Blood Cells 89 in plasma, fibrinogen neutralizes the charges on red In Westergren method: cells, thereby removes the repelling forces. In some pathological conditions, in addition to fibrino- Physiological Variations gen, few other plasma factors called as acute phase-re- 1. These phase reactants increase in plasma fibrinogen content also neutralize the charges on the red cell surface and 2. When, the medium for sedimentation (the plasma) like hereditary spherocytosis and sickle cell disease becomes thicker, rate of sedimentation decreases. The cells are highly deformable due to presence of ankyrin and spectrin in the membrane skeleton. Deformability of the red cells allows them to pass through capillaries and splenic pulp. Change in shape and rigidity of the membrane make the red cells susceptible to hemolysis. Also, biconcave shape and membrane plasticity help red cells to resist osmotic lysis (less osmotically fragile). In infection, inflammation, malignancy and collagen diseases, the inflammatory or abnormal proteins produced by the disease neutralize the negative charge and facilitate rouleaux formation. When a student fails to answer the size and shape of normal red cells, basics of red cells, and normal red cell count, it becomes difficult for examiner to give the pass marks. Define erythropoiesis, give the stages and sites of erythropoiesis, and differentiate extramedullary from medullary erythropoiesis. Describe different steps of erythropoiesis with the help of schematic diagram of cells. Give the source, mechanism of action and functions of erythropoietin, and regulation of erythropoietin secretion. Give the structure and normal count of reticulocyte and alteration in reticulocyte count in different conditions. From the 5th week of gestation, erythropoiesis takes place the new cells are formed at a pace that replaces the cells in the liver and spleen (hepatic stage). Bone marrow precisely replaces the cells lost by senescence, hemorrhage or destruction. Red cell mass in a Medullary Stage normal man is 26–32 ml/kg and in women 23–29 ml/kg of From the 5th month of intrauterine life, the bone marrow body weight. The volume of red cells (red cell mass) in the starts forming red cells (medullary stage). After birth, bone marrow becomes the Definition: Erythropoiesis is defined as the process of for­ sole site of erythropoiesis. Till adolescent period, marrow cavities of all bones are Stages of Erythropoiesis involved in erythropoiesis, after which erythropoiesis There are three stages of erythropoiesis: mesoblastic, regresses in the limb bones. After the age of 20–30 years, erythropoiesis is mostly limited to sternum, ribs, vertebrae, skull, pelvic and Mesoblastic Stage pectoral girdles (Refer to Fig. During intrauterine life, erythropoiesis first takes place in Important Note the mesoderm of yolk sac and mesoderm of the body. Extramedullary erythropoiesis after birth is abnormal: After This is called mesoblastic stage.

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Many of these defenses beneath the basement membrane and the reticular dermis is are general or nonspecifc and do not require previous expo- beneath the papillary dermis order kamagra effervescent 100 mg without prescription. Both the papillary and reticular sure to the offending pathogen (or closely related organism) kamagra effervescent 100mg sale. Another important defense system is acquired immunity cost of kamagra effervescent, which can develop after previous contact the epidermis is the upper layers of the skin that contain with the organism through infection (overt or subclinical). Early induced responses are nonadaptive host responses induced by infectious agents early in infection. Their induc- the keratin layer is an external structure of skin that pro- tive phase differentiates them from innate immunity and their tects the body from microorganisms and resists penetrating failure to involve clonal selection of antigen-specifc lympho- stimuli. It is comprised of keratin protein flaments synthe- cytes distinguishes them from adaptive immunity. Innate defense system is general or nonspecifc and does Keratinocytes are squamous epithelial cells of the epider- not require previous exposure to the offending pathogen (or mis that are produced in waves. The keratin layer is a Constitutive defense system: Refers to innate or constitu- consequence of the orchestrated death of a wave of keratino- tive defense system. In the lower epidermis, these cells secrete pro-infam- matory cytokines and complement components. Innate immunity is a natural or native immunity that is present from birth and is designed to protect the host from Desmosomes are specialized junctions that connect kerati- injury or infection without previous contact with the infec- nocytes to one another and guarantees that each keratinocyte tious agent. It is attributable to physical, chemical, and layer divides and migrates upward as a unit. It includes such factors immunity, may have a signifcant role in resistance of a group as protection by the skin, mucous membranes, lysozyme in (herd) of humans or other animals against an infectious dis- tears, stomach acid, and numerous other factors. Elimination of reservoirs of the disease agent natural killer cells, complement, and cytokines represent key may be as important as specifc immunity in diminishing participants in natural innate immunity. The successful vaccination infected under normal circumstances by selected microor- of most members of a population against a selected pathogen ganisms that usually infect animals. This may be altered in may protect non-immune individuals in the group, whose the case of profound immunosuppression of humans, as in vulnerability is diminished because the pathogen cannot the case of acquired immune defciency syndrome in which become established in the vaccinated population. Molecules, Cells, and Tissues of the Immune Response 153 Lactoferrin is a protein that combines with iron and com- Protective immunity refers to both natural, nonspecifc petes with microorganisms for it. This represents a nonanti- immune mechanisms and actively acquired specifc immu- body humoral substance that contributes to the body’s natural nity that result in the defense of a host against a particular defenses against infection. By combining with induced either by active immunization with a vaccine pre- iron molecules, it deprives bacterial cells of this needed pared from antigens of a pathogenic microorganism or by substance. Lactoperoxidase is an enzyme present in milk and saliva that may be inhibitory to a number of microorganisms and Protective antigens are the antigenic determinants of a serves as a nonantibody humoral substance that contributes pathogenic microorganism that stimulate an immune response to nonspecifc immunity. Its mechanism of action resembles that can protect a host against an infection by that microor- that of myeloperoxidase. Thus, these particular antigenic specifcities can be used for prophylactic immunization in vaccines to immunize Nonsterile immunity: See premunition. Acquired immunity is protective resistance against an Protective epitopes are antigenic determinants of a patho- infectious agent generated as a consequence of infection with genic microorganism that stimulate a protective immune a specifc microorganism or as a result of deliberate immu- response against that same microorganism. Preemptive immunity refers to resistance shown by virus- Cellular immunology is the study of cells involved in infected cells to superinfection with a different virus. Artifcial passive immunity refers to the transfer of immu- Active immunity is protection attained as a consequence of noglobulins from an immune individual to a nonimmune, clinical or subclinical infection or deliberate immunization susceptible recipient. It is a type of adaptive immunity in which lymphocytes are activated in response to Passive immunity is a form of acquired immunity induced a foreign antigen to which they have been exposed. Compare by the transfer of immune serum containing specifc anti- with passive immunity. Examples of passive immunity Artifcially acquired immunity is the use of deliberate are the transfer of IgG antibodies across the placenta from active or passive immunization or vaccination to elicit pro- mother to fetus or the ingestion of colostrum-containing anti- tective immunity as opposed to immunity which results from bodies by an infant. Antitoxins generated to protect against unplanned and coincidental exposure to antigenic materials, diphtheria or tetanus toxins represent a second example of including microorganisms in the environment. The trans- fer of specifcally sensitized lymphoid cells from an immune Specifc immunity refers to an immune state in which anti- to a previously nonimmune recipient is termed adoptive body or specifcally sensitized or primed lymphocytes recog- immunization. By contrast, immunologically serum can be used for the temporary protection of individu- competent cells may interact with antigen to produce specifc als exposed to certain infectious disease agents. Humoral immune response is a host defense mediated by antibody molecules found in the plasma, lymph, and tissue Gravity and immunity: Space fight has been associated fuids. This type of immunity protects against extracellular with the development of neutrophilia, slight T cell lym- bacteria in foreign micromolecules. Humoral immunity may phopenia, and diminished blastogenic responsiveness of be transferred passively with antibodies or serum containing T cells in postfight blood samples. Changes have also Humoral antibody is found in the blood plasma, lymph, been observed in postfight concentrations of immuno- and other body fuids. Humoral antibody, together with com- globulins, complement components, lysozyme, interferon, plement, mediates humoral immunity which is based upon and α2-macroglobulin. IgA and IgM rose but IgG remained constant dur- immunodefciency worldwide is malnutrition. No defects in humoral immunity have malnutrition has an adverse effect on immunity, increases been noted. Serum antibody responses are usually unaffected in Exercise-induced immunosuppression or immunoenhance- protein-energy malnutrition. But cytes is intact and metabolic destruction of microorganisms these increases return to preexercise levels within a few is decreased as is synthesis of various cytokines including hours following its cessation. Acute exercise is followed cell-mediated immunity and diminished antibody responses. It leads to impaired lympho- have been demonstrated following long distance running. IgG, IgM, and IgA levels as well as the ability to synthesize antibody to tetanus toxoid antigen are not compromised by Vitamin A and immunity: A defciency of vitamin A com- exercise. Exercise prior to exposure to infection diminishes promises acquired, adaptive, antigen-specifc immunity. The morbidity or mortality, yet exercise during an infection pro- defciency has been linked to atrophy of thymus, spleen, duces the reverse effect. Prolonged intense exercise is fol- lymph nodes, and Peyer’s patches pointing to major alterations lowed by some immunosuppression. Vitamin A defciency altered by physical exercise are related to the neuroendocrine is also associated with impaired ability to form an antibody changes such as those that occur in response to physical or response to T cell-dependent antigens such as tetanus toxoid, psychological stress. It is also linked to decreased antibody responsiveness to T cell-independent antigens such Nonspecifc immunity: Refers to mechanisms such as as pneumococcal polysaccharide and meningococcal poly- phagocytosis that nonspecifcally remove invading micro- saccharide. Vitamin A defciency also compromises natural organisms, as well as the action of chemical and physical innate immunity since it is necessary for maintenance of barriers to infection such as acid in the stomach and the mucosal surfaces, the frst line of defense against infection. Other nonspecifc protective factors include lysozyme, Immune effector cells that mediate nonspecifc immunity β lysin, and interferon. Nonspecifc or natural immunity include polymorphonuclear cells, macrophages, and natural does not depend on immunologic memory. Neutrophil phagocytosis is diminished by cells represent an important part of the natural immune Vitamin A defciency, and viral infections are more severe cell system.

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