Antigens are molecules that trigger an acquired immune response. They include proteins, lipids, carbohydrates, and nucleic acids from pathogens like bacteria and viruses. A good antigen is chemically stable, complex, particulate, foreign, and elicits a strong immune response depending on factors like dose, route of administration, and host genetics. Antigens are recognized by antibodies through epitopes, the specific sites on antigens that antibodies bind to. Haptens are small molecules that are not immunogenic alone but can elicit an immune response when attached to a carrier protein.

1. ANTIGENS: TRIGGERS OF AQUIRED IMMUNITY

2. PATHOGEN. Organism that cause a disease. VIRULENCE. Ability to cause disease. PATHOGEN. Organism that cause a disease PRIMARY PATHOGEN. Organism that cause a disease almost every time it invades a healthy individual. SECONDARY PATHOGEN. Organism that cause a disease only if the immune response is impaired.

6. Pinchuk: Schaum’s Outline of Theory & Problems of Immunology. The McGraw−Hill Companies, 2004

8. ANTIGEN ( Anti body gen erator) Antigen (Ag) Ab

9. ANTIBODY (Ab = Anti gen b inding) Antibodies do not bind to the whole agent Binds to one of many molecules (Ag) Many for one organism Binds to a restricted part of the Ag (Epitope) Ag has many epitopes (different or repeated)

10. ANTIBODY (Ab = A ntigen b inding) Antibodies do not bind to the whole agent Binds to one of many molecules (Ag) Many for one organism Binds to a restricted part of the Ag (Epitope) Ag has many epitopes (different or repeated)

11. Flagellum H Ag Pili F Ag Capsule K Ag Cell wall O Ag Cell membrane Ribonucleo- protein Structure of a bacterium and the localization of important Ag Cell sap, enzymes

12. 0 Ag Lípid A Porin Cell membrane Cell wall polysaccharide Peptidoglycan (*NAG, NAM) Cell membrane KDO The basic structure of cell walls NAG= N -acetyl glucosamine NAM= N -acetyl muramic acid Gram-positive Gram-negative

13. Envelope (lipoproteins glycoproteins) Core (nucleic acid) Capsomers (good Ag) The structure of a virus (important Ag)

14. NONMICROBIAL ANTIGENS

15. CELL-SURFACE ANTIGENS Blood group Ag AB O RBC A A B B Rh Rh Factor (Rhesus macacus) A +/- B +/- AB +/- O +/-

16. CELL-SURFACE ANTIGENS MHC I Endogenous Ag MHC II Exogenous g MAJOR HISTOCOMPATIBILITY COMPLEX Nucleated cell

17. WHAT MAKES A GOOD ANTIGEN? Antigenicity Chemical Stability Complexity Particulate vs. Soluble Denatured vs. Native Foreignness Protein. Lipids. CHO’s Nucleic acids. Size Host genetics Route of administration Dose Adjuvant

19. DR. POLLY MATZINGER An innate sense of Danger The immune system has two questions to answer when faced with a potential pathogen. 1. Shall I respond?? 2. how does the immune system know what kind of response to make? Galadriel Mirkwood

20. 1 nm Glucose Angiotensin 1.03 kDa Albumin 66 kDa Inmunoglobulin G 160 kDa Fibrinogen 400 kDa Inmunoglobulin M 900 kDa Relative sizes of several Ag

21. EPITOPE OR ANTIGENIC DETERMINANT (immunodominant region of a molecule) Microorganism (huge Ag collection) epitope

23. HAPTENS (Greek haptein = to grasp or fasten) DINITROPHENOL = (DNP) NOT IMMUNOGENIC BECAUSE < 1,000 Da

24. Native epitope Carrier protein Several epitopes attached to a peptide chain. DNP Hapten molecule

26. PENICILLIN EXAMPLES OF HAPTENS Chronic dermatitis, hair loss, and depigmentation.

27. EXAMPLES OF HAPTENS POISON IVY ( Rhus radicans ) = allergic contact dermatitis

28. EXAMPLES OF HAPTENS CHROME NICKEL

29. EXAMPLES OF HAPTENS Resins or latex

30. Bacteria or Food carrying epitope A Group A blood transfusion Severe transfusion reaction Food or bacteria Ag in diet carry epitopes that cross-react with blood group A. Animal of group blood O makes Ab to A epitope despite never having received group A red cells. Blood group O Ab to blood group A Ouch!!!