Comprehensive Overview of Immunology and Immunity

1. IMMUNOLOGY Immunology- Immunity, Definition, Classification, General principles of natural immunity, Phagocytosis, acquired immunity (active and passive) . Antigens, chemical nature of antigens structure and formation of Antibodies, Antigen-Antibody reactions. Bacterial exotoxins and endotoxins. Significance of toxoids in active immunity, Immunization programme, and importance of booster dose

2. IMMUNOLOGY Terminologies Branches of immunity Infection Factors influencing infection Antigen antibody reaction MHC Official Bacterial & Viral Vaccines Diagnostic preparations Schick test toxin, Schick control, Old tuberculin,Tuberculin PPD

3. Terminologies

6. Branches of immunity After clinical infection Natural - part of body make up Naturally acquired Active – developed and last slowly After Sub clinical infection Immunity Artificially stimulated - By injection of antigen cont prep Vaccines Acquired -added during life time Naturally Acquired - Acquired from mother Passive – produced and lost quickly Artificially produced - By injection of antibody cont prep sera / human immunoglobulin

7. Develops slowly, it is not fully effective for several weeks. Once developed, long lasting and gives protection for many years Even when it begins fade a booster dose may be enough to stimulate Induced by infection or by immunogens Immunity effective only after lag period Immunological memory present Negative phase may occur Not applicable in the immunodeficient Develops quickly Protection last with in two to three weeks The rate of elimination is much lower Readymade antibody transferred Immediate immunity No memory Subsequent dose is less effective No negative phase Applicable in the immunodeficient Active immunity Passive immunity

8. Cells of immune system • Lymphocytes -have ability to interact specifically with antigenic subs – present mainly in peripheral blood & lymphoid tissues • B – Lymphocytes – B Cells – they carry IG on their cell membrane which function as antigen receptor – plasma cells • T – Lymphocytes – T cells – thymus – they carry an antigen recognition unit on their membranes (TcR) – regulation of immune resp

9. Plasma cells – eccentric nuclei with clumped chromatin with a large cytoplasm with abundant endoplasmic reticulum. They produce and secrete large amounts of immunoglobulins. Found in bone marro, lymphoid tissues • Natural killer cells – large granular lymphocytes, they don’t carry any antigen receptors but they recognize antibody molecules bound to target cells and destroy those cells

10. Antigen presenting cells – Monocytes, Macro phages and Dentric Cells. Monocyte is considered as leukocyte which transit through the blood, when fixed in a tissue it becomes macrophages- able to ingest particulate matter – they concentrate antigen fragments in the cell membrane • Granulocytese – Collection of WBC – Neutrophils, Eosinophils, Basophiles

11. INFECTION • Physical contact with a diseased person or animal – veneral diseases • Droplet infection – Coughing, sneezing • Dust borne infection – Mycobacterium tuberculosis • Contact with contaminated articles – cloths, bedding, towel, toys • Hand infection • Arthropod Vectors – flies, mosquitoes

12. Factors influencing Infection • Virulence – 1.multiplication 2. toxins • Invasiveness, aggressiveness, toxigenicity, pathogenicity • Exotoxins • Metabolic Product of actively growing bacteria • Mainly by G+ve bacteria • Water soluble – can be removed by bacteria proof filters • High molecular wt proteins • Extremely toxic – botulinus toxin – dangerous food poison – I mg is enough to kill 20 million mice

13. Ex of exotoxin producing bacteria • Clostridiumtetani,C.Botulinium,C.perfringens, Corynebacteriumdiphtheria , • (Tetanus, Gas gangrene, Diphtheria) • Endotoxins • Structural element of bacteria • Mainly G-Ve bacteria – excreted after death • Chemically phospholipids, polysaccharides, protein • Less toxic • Ex of endotoxin producing bacteria • Vibrio cholerae, Pasteurella pestis, S.typhi, B.pertusis • (Cholerae, Plague, Typhoid, Whooping cough)

14. The number of organisms • Route of entry (alimentary track, genito urinary track, respiratory trcak) • The resistance of the host • Prevention of entry • Phagocytosis • Antibody production

15. Antigens • Any substance when introduced parenterally into the body, stimulates the production of an antibody • Some chemical that creates immune response • Most are proteins or large polysaccharides from a foreign organism. • Microbes: Capsules, cell walls, toxins, viral capsids, flagella, etc. • Nonmicrobes: Pollen, egg white , red blood cell surface molecules, serum proteins, and surface molecules from transplanted tissue.

16. Antigens Epitope: • Small part of an antigen that interacts with an antibody. 10-12 amino acids • Any given antigen may have several epitopes. • Each epitope is recognized by a different antibody.

17. Epitopes: Antigen Regions that Interact with Antibodies

18. Antibodies • Proteins that recognize and bind to a particular antigen with very high specificity. • Made in response to exposure to the antigen. • One virus or microbe may have several antigenic determinant sites, to which different antibodies may bind. • Each antibody has at least two identical sites that bind antigen: Antigen binding sites. • Belong to a group of serum proteins called immunoglobulins (Igs).

19. Antibody Structure • Monomer: A flexible Y-shaped molecule with four protein chains: • 2 identical light chains • 2 identical heavy chains • Variable Regions: Two sections at the end of Y’s arms. Contain the antigen binding sites (Fab). Identical on the same antibody, but vary from one antibody to another. • Constant Regions: Stem of monomer and lower parts of Y arms. • Fc region: Stem of monomer only. Important because they can bind to complement or cells.

20. Antibody Structure

21. How Do B Cells Produce Antibodies? • B cells develop from stem cellsin the bone marrow of adults (liver of fetuses). • After maturation B cells migrate to lymphoid organs (lymph node or spleen). • Clonal Selection: When a B cell encounters an antigen it recognizes, it is stimulated and divides into many clones called plasma cells, which actively secrete antibodies. • Each B cell produces antibodies that will recognize only one antigenic determinant.

22. Humoral Immunity Apoptosis • Programmed cell death (“Falling away”). • Human body makes 100 million lymphocytes every day. If an equivalent number doesn’t die, will develop leukemia. • B cells that do not encounter stimulating antigen will self-destruct and send signals to phagocytes to dispose of their remains. • Many virus infected cells will undergo apoptosis, to help prevent spread of the infection.

23. Overview of the Immune Response

24. Antigen antibody reaction • The sites on the Ag molecule that combine with the binding site of an Ab are known as epitopes. • Chemical bonds responsible – Electrostatic bonds, Hydrogen Bonds, Hydrophobic interactions, VanderWalls bonds

25. Antigen antibody reaction

26. Official bacterial & viral vaccines Diphtheria Staphylococcus Tetanus Cholera Pertussis Plague Typhoid Toxoids Killed Bacterial Official vaccines Attenuated Bacillus Calmette Gurein Susp of micro-orga Killed Typhus Rickettsial Influenza Measles Poliomyelitis Rabies Killed Viral Measles Poliomyelitis Yellow fever Small pox Attenuated

27. Significance of toxoids in active immunity A toxoid is a bacterial TOXIN(usually an exotoxin) whose toxicityhas been inactivated or suppressed either by chemical (formalin) or heat treatment, while other properties, typically immunogenicity, are maintained. Thus, when used during vaccination, an immune response is produced against toxoid without resulting in toxin-induced illness. Anatoxin or Anatoxine. - These are toxoids for prevention of diphtheria, tetanus and botulism Toxoids are used as vaccines because they induce an immune response to the original toxin or increase the response to another antigen since the toxoid markers and toxin markers are preserved. For example, the tetanus toxoid is derived from the tetanospasmin produced by Clostridium tetani.

28. Importance of booster dose In medicine, a booster dose is an extra administration of a vaccine after an earlier dose. After initial immunization, a booster injection or booster dose is a re-exposure to the immunizing antigen cell. It is intended to increase immunity against that antigen back to protective levels after it has been shown to have decreased or after a specified period. For example, tetanus shot boosters are often recommended every 10 years.If a patient receives a booster dose but already has a high level of antibody, then a reaction called an Arthus reaction could develop, a localized form of Type III hypersensitivity