Immunology Lecture 3 PDF

1  Ouchterlony double diffusion * Uses: Determine antigenic relationship between substances * Types: A- Pattern of identity: 1- Central well (Abs ) & peripheral wells (identical Ags.) 2- One continuous, coalescing ppt. line...

1  Ouchterlony double diffusion * Uses: Determine antigenic relationship between substances * Types: A- Pattern of identity: 1- Central well (Abs ) & peripheral wells (identical Ags.) 2- One continuous, coalescing ppt. line B- Pattern of non-identity: 1- Central well (Abs) & peripheral (unrelated Ag 1 & 2 ) 2- Each Ag forms ppt line with corresponding Ab (lines cross each other) C- Pattern of partial identity: 1- Ag1 & Ag2 share epitopes, with Ag1 having more 2- Abs + Ag1 ----> ppt line 4- Some of Abs + Ag2 ---> line of identity (coalescence) 5- Abs not bind Ag2 --> pass ppt line, combine with Ag1 ---> spur 3- Immunoelectrophoresis: Principle: Electrical separation mix. of proteins (Ags) -----> detection with Abs Steps: 1- Electrophoretic separation 2- Diffusion 3- Immune precipitation Neutralization reactions Uses: detection bacterial toxins & Abs to viruses 1- Schick test: for diphtheria toxin 2- Viral neutralization: for virus infection 2/10 3/10 Complement Fixation Test (CFT) * Application: detection of Abs & diagnose of microbial infections * Steps: 1- Inactivation of patient complement by heating 2- Add non-human complement & test Ag 4- Indicator system (sheep RBCs + Anti-sheep RBCs) added Results: + ve: Ab present ---> comp. fixed ---> NO hemolysis - ve: Ab absent ---> comp. fixed by indicator sys. ---> hemolysis Tagged Ab tests Adv.: Sensitive tests to detect Abs or Ags Principle: Abs with molecular tag detect Ag at low conc. 1- Western blots (Immunoblots) 1- Ags separated in gel (immunoelectrophoresis) 2- Abs (serum patient) added -----> binds with Ags [Ab labeled (e.g. with radioactivity or enzyme)] 3- Substrate added --------> colored bands 2- Radioimmunoassay (RIA) Radioactively tagged Ab added 3- Immunofluorescence Abs tagged with fluorescent dye Anti-Ab has enzyme taG 4- Enzyme-Linked Immunosorbent Assay (ELISA) (e.g Horseradish Peroxidase; HRP)  CD (Cluster of Differentiation) 4/10 Description: 1- Surface markers designated CD 2- Nomenclature system for Identification & characterization of cells e.g: a- CD4 on Helper cells (TH1 & TH2). b- CD8 on cytotoxic cell (Tc) & T suppressor (Ts) cell. 2- Cell-mediated (Cellular) Immunity * Involves: 1- Direct action of T-cells (T-cells interact directly with cells displaying Ags) 2- T-cells do not make Abs (C.F: B-cells) 3- Production of lymphokines * Interactions: 1- Clear pathogens (intracellular) 2- Rejection of tumor cells 3- Some allergic reactions 4- Immune response to transplanted tissues Antigen-presenting cells (APC) * Function: Process & present Ag to T-cells (e.g. Macrophages) * Characters: Have MHC class I & II (major histocompatibility complex) responsible for: A- Ag presentation: MHC I present Ags to TC cells & MHC II to TH cells B- Rejection or acceptance of transplanted tissue  5/10 Cell-Mediated Immune Reaction 1- Macrophages process & present Ag. to T-cells 2- T-cells ---> divide ----> different types of T-cell A- TC cells & NK cells ---> Killing infected cells B- T-memory cells ---> rapid subsequent response C- TH cells -----> Lymphokines D- TS cells -----> suppress TH cells Lymphokines: chemical substances trigger certain immunologic Rxns. e.g: Macrophages secrete IL-1 --> activates TH cells -> IF & IL-2 3- TH cells: A- Bind & activated by [MHC class II-Ag] on macrophage C- Differentiate into: TH1 cells ---> activate macrophage TH2 cells ---> activate B-cells 4- TD (delayed hypersensitivity T-cells): A- Participates in delayed hypersensitivity B- Release various lymphokines: i- Macrophage chemotactic factor --> helps macrophages find microbes ii- Macrophage activating factor --> Stimulates phagocytic activity iii- Macrophage aggregation factor --> enhances macrophages aggregation iv- Migration inhibitory factor --> Prevents macrophages leaving sites  Extracellular killing Eosinophils: 1) Worms are destroyed extracellularly (without being ingested) 2) Eosinophil ------> Major Basic Protein (MBP) ----> worm damage (Antiparasitic) 3) Once destroyed, macrophages engulf parasite fragments Complement * Characters: 1- > 20 proteins produced by liver & circulate in plasma in inactive form 2- Nonspecific (exert same defensive effects regardless of m.o ) & works as cascade 3- Of 20 proteins: 13 participate in cascade, 7 activate or inhibit Rxns in cascade Function 2 pathways: Classical pathway & Alternative pathway (or properdin pathway). A- Classical pathway: 1- Begins when Abs bind to Ags 2- Involves C1, C4 & C2 B- Alternative pathway: - Activated by complement proteins (Factor B, D & P (properdin) & polysaccharides at pathogen surface. Both: Activate reactions involving C3 through C9 & have same effect C3 (key protein) ----> splits into C3a & C3b -----> participate in 3 defenses: 1- Opsonization 2- Inflammation 3- Membrane attack complexes (MAC) 6/10  1- Opsonization 7/10 1- Some bacteria with capsule or surface M proteins can escape phagocytes 2- Abs called opsonins coat microbial surface (opsonization or immune adherence) 3- C1 binds to these Abs, initiating cascade: - C3b binds to m.o & phagocytes ----> phagocytosis 2- Inflammation - C3a, C4a & C5a: A- Stimulate chemotaxis ---> inflammation & phagocytosis B- Adhere to basophils & mast cells --> histamine --> permeability of B.V 3- Membrane Attack Complexes (MAC) - C3b causes cell lysis (immune cytolysis) -> assembly of 15 C9 molecules in CM ----> Pore formed -> MAC --> Lysis of m.o  Immunization Types: 1. Active immunization: by administration of Ag (vaccines or toxoids) 2. Passive immunization: by Ab from immunized individual Mechanisms of active immunization 1- Vaccine or toxoid: keeps antigenicity but lacks pathogenicity 2- Vaccine or toxoid administered ---> Abs or TC & memory cells 3- Vaccines made with live organisms ---> longer-lasting immunity 4- Booster shots maintain immunity: Vaccine (Type) Immunity 1st dose ---> stimulates 1ry immune response Measles vaccines Life long OPV (live viruses) Subsequent doses --> stimulate 2ry immune response IM polio vaccine (killed virus) 3 - 5 yrs 5- Active immunization NOT prevent disease if person has Typhoid vaccine (dead bacteria) exposed: time for immunity to develop is > disease I.P Tetanus & diphtheria toxoids About 10 yrs Hazards of vaccines * Symptoms: - Fever, malaise, soreness (at inj. site), allergic Rxn., Joint pain & Convulsions * Precautions: - Patients suffering from fever & malaise NOT receive immunization ---> worsening - Small No. die or suffer from permanent damage (e.g. OPV) - Live vaccines --> hazards to pregnant women --> birth defects hazards to immunodeficient patients 8/10  Passive Immunization * Characters: 1- Immediate immunity (quick but temporary) 2- Ready-made Abs: Products called antisera (Abs found in serum protein) A- γ-globulin (Immune serum globulin): Pooled from many individuals contain Abs to common diseases (e.g: measles) B- Hyperimmune serum (convalescent sera): γ-globulins have high titers of specific kind of Abs (e.g: Anti-mumps Abs) C- Antitoxins: Abs against specific toxins (e.g: Diphtheria) 3- Anti-Rh-Abs given to Rh -ve mother within 72 h after birth of Rh +ve child --> bind Rh +ve RBCs ---> destroyed before mother immune system makes Abs to them) Hemolytic disease of newborn (Erythroblastosis fetalis) * Mechanism: 1- Rh-ve mother carries Rh+ve fetus --> Fetal Rh Ag can across placenta (delivery, miscarriage,….) 2- Mother ---> Anti-Rh Abs --> 1st child rarely suffers hemolytic disease 3- Subsequent pregnancies: sensitized mother --> Anti-Rh Abs (IgG) ---> cross placenta ---> Type II Rxn. in Rh+ve fetus * Result: Hemolytic disease of newborn * Symptoms: 1- Enlarged liver & spleen 2- Jaundice (excessive bilirubin) Hazards of passive immunity * Allergy: (e.g. Antitoxin prepared in animals --> allergic Rxns to large IgG if accidently given I.V instead I.M) 9/10 Thanks