Immunity: acquired protection The basis for vaccination

Learning objectives compare the humoral and cell mediated immune responses compare the humoral and cell mediated immune responses describe how phagocytic cells protect against pathogens and how bypass these defense mechanisms describe how phagocytic cells protect against pathogens and how bypass these defense mechanisms explain the basis for the specificity, memory and tolerance of the immune response explain the basis for the specificity, memory and tolerance of the immune response distinguish between passive and active, natural and acquired immunity distinguish between passive and active, natural and acquired immunity

Features of immunity

PAMPS Overview of immunity

What substances stimulate an immune response? Any substance that stimulates an immune response is an antigen Any substance that stimulates an immune response is an antigen n Usually protein or polysaccharide over 1000 mw n may be whole cell or part or toxin composed of antigenic determinants (epitopes) which evoke specific immune responses composed of antigenic determinants (epitopes) which evoke specific immune responses Haptens - small molecules that attach to larger ones and act as antigenic determinant Haptens - small molecules that attach to larger ones and act as antigenic determinant

Antibody structure n Variable and constant regions n Fc region n Monospecific and bivalent

How are antibodies produced? Antigen processing and presentation by macrophages or other Antigen processing and presentation by macrophages or other antigen-presenting cell with class II MHC Specific helper T cell recognizes antigen MHC II Macrophages release interleukin 1 (Il-1); Th releases Il-2 ;Th activates specific B cells that have bound antigen to grow and differentiate into plasma cells and specific memory cells Plasma cells produce antibody Memory cells remain for faster secondary response (5 - 7 days) Plasma cells

Cell mediated immunity

Cytotoxic T cell n Recognition of MHC1- ag n Killing by two mechanisms

Superantigens n Activate T cells by binding to conserved regions of MHCII and TCR n Binds to large numbers (5 - 25%) compared to conventional ag (<.01%) n Extensive cytokine production Massive inflammationMassive inflammation Shock (TSS)Shock (TSS)

Autoimmunity n Why do such mistakes occur? n Hashimoto’s n Addison’s n Infertility n Juvenile diabetes n Multiple sclerosis n Ulcerative colitis n Rheumatoid arthritis