chap 17 Flashcards
what are antigens
- molecules that activate lymphocytes by identification
- b cells interact w surface immunoglobins(antibodies)
- t cells interact w surface antigen receptors
what allows for the interaction with antigens
epitopes/ determinants
- specific binding sites of antigen
- elicit immune response( can be protein, peptide or
complex polysaccharide)
antibody structure
- variable regions - possess variable amino acid
sequence that acts as antigen binding sites
- can change
- 2 amino acid on each end - Fc region bind to host cell receptor
antibody classes
- IgA(15%) - dimer(4 binding sites per), mainly on
mucosal surfaces and secretions. prevent
attachment to surfaces - IgG(75%) - monomer; most in blood and tissue fluid;
opsonization, activate complement; neutralize
viruses - IgD(0.2%) - on B cells(in blood), lymph
- IgM(10%) - circulating type pentamer; in blood vessels
mostly. first ab detected in response; does
agglutination and complement activation
- clump up around pathogen and signal others - IgE(0.2%) - on surface mast cells and basophils; cause
release histamine and other chems. attract
complement and phagocytic cells. found outside
blood
which antibody classes are not monomers
IgM and IgA
humoral immune response
- composite of responses to different epitopes by b
cells - most effective against extracellular pathogens
clonal selection
- increase of b cells to respond to antigen
- b cell contact cognate(matching) antigen, it divide to
plasma cells(that secret antibodies) and memory cells
t-independent antigen
- antigen that no need t helper cell for b cell to produce
IgM - only produces IgM
steps of humoral immune response
- b cell w ig receptor bind antigen
- show MHC class II
- helper t cell attach
- helper t cell release cytokines
- cytokinins make b cell divide to memory and plasma
cells
plasma cell
- type of b cell that release soluble version of antibody to attach to pathogen and signal
- make IgM -> IgG
antibody responses
- primary antibody response -
- after infection/vaccination; antibodies appear in
serum
- during lag, b cells bind to antigen(makes plasma
cells and memory b cells) - secondary response -
- by second exposure or booster
- w memory b cells promote bigger response w IgG
- why immunization works
- faster than primary
mechanisms of binding antibodies and antigens
- agglutination - clump bacteria together to deal w
together - opsonization - coat bacteria w antibody that promote
phagocytosis - neutralization - block bacteria attack to mucosa/ block
attachment of toxins - activation of complement - cause inflammation and
cell lysis - antibody dependant cell mediated cytotoxicity-
pathogen antibody attract diff methods to get rid
cell-mediated immunity
- involve t cell
- recognize antigen on cell surface that are infected w intercellular pathogens(virus infected cells)
cytotoxic t cells(ctls)
- differentiate in to cytotoxic t lympocytes
- target cells self altered by infection(virus and bacteria)
- also target cancer cells
- activated by mhc class I + processed antigen by CTL
CD8+ co-receptor - make channel(perforin protein) for granzymes to
cause apoptosis
T helper cells
- recognize antigens presented by apc(dendritic cells
and macrophages) - use CD4+ co-receptor to bind antigen w MHC class II
on apcs - activation = release cytokines
- tH1: activate macrophages, complement,
inflammation, opsonization, and divide CTLs
- tH2 : cytokines for antibody prod fr b cells
naturally acquired active immunity
- antigens enter body naturally; body make anitbodies
naturally acquired passive immunity
- antibodies pass fr mother to child via placenta or as infant
artificially acquired active immunity
- antigens intro by vaccines so body produce antibodies
artificially acquired passive immunity
- preformed antibodies in immune serum injected to
body
IgA
IgA(15%) - dimer(4 binding sites per), mainly on
mucosal surfaces and secretions. prevent
attachment to surfaces
IgG
IgG(75%) - monomer; most in blood and tissue fluid;
opsonization, activate complement; neutralize
viruses
IgD
IgD(0.2%) - on B cells(in blood), lymph
IgM
IgM(10%) - circulating type pentamer; in blood vessels
mostly. first ab detected in response; does
agglutination and complement activation
- clump up around pathogen and signal others
IgE
IgE(0.2%) - on surface mast cells and basophils; cause
release histamine and other chems. attract
complement and phagocytic cells. found outside
blood
