Is the aspect of immunity that is mediated by antibodies produced by Plasma cells
The production of antibody involves three distinct phases 1 Induction phase: Ag reacts with specific T and B cells 2 Expansion and Differentiation phase: Lymphocyte clones proliferate and mature to a functional stage 3 Effector phase: Antibodies exert biological effects
1 B cells recognize antigen via surface antibody (B cell receptor)2 Ag is internalized , processed and expressed on the surface of the B-cell (and other APCs) in association with MHC II molecules3 Antigen is recognized by T-helper cells (CD4+)4 T cells are activated and differentiated into TH2 cells
5 The stimulated T-cells then releaselymphokines that act upon "primed" B-cells (B-cells that have alreadyencountered antigen), inducing B-cellproliferation and differentiation intoPlasma cells6 Plasma cells begin to secrete IgM
Types of humoral response•Primary response: Begins immediately Predominantly IgM Appears 48 to 72 hours later•Secondary response: Occurs within 24 to 48 hours Predominantly IgG. Persists much longer Result of repeated contact withantigens
Primary Response:•Slow in Onset Secondary Response:•Low in Magnitude Rapid in Onset•Short Lived High in Magnitude•IgM Long Lived IgG (Or IgA, or IgE
Monoclonal Antibodies Recognize only one epitope on an antigen Polyclonal Antibodies Recognize multiple epitopes on any one antigen
Functions of Antibodies1 Bind to and neutralize toxins —basis of Passive Immunization2 Bind to and agglutinate pathogens Prevent them from entering or damaging the cells3 Opsonize pathogens4 Cause complement dependent killing5 Mediate ADCC6 Provide passive immunity to fetus
Disease Diagnosis1 Demonstration of Antibodies against aspecific pathogen is diagnostic of thatdisease eg viral and bacterial diseases Basis of serological tests2 Detection of Autoantibodies inautoimmune diseases
Therapeutic Applications Targeted monoclonal antibody therapy is employed to treat diseases such as rheumatoid arthritis, multiple sclerosis, psoriasis, and many forms of cancer Treatment of Immune Deficiency diseases by Passive Immunization (human serum) Use of Anti-RhD antibodies to prevent Hemolytic Disease of Newborn
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