Humoral Immunity: Antigen Recognition (Detection) Flashcards
Humoral Immunity: Detection 1. FcRn sequestration 2. Oposonization 3. Cytotoxicity 4. IgE and helminths 5. Complement Pathways a. classic pathway b. alternative pathway c. lecithin pathway 6. Complement Effects a. f(x): antimicrobial, B-activation b. regulation: DAF and C1 inhibitor
clonal expansion
activation and proliferation of b cells with receptors specific to the pathogenic agent
plasma cells
mature B-lymphocytes that reside in bone marrow but secrete antibodies into plasma specific for antigen
heavy-chain isotype switching
expression of heavy chains appropriate for an infectious agent due to cytokines from Helper T cells
affinity maturation
the process of generating antibodies with increasingly high affinity after repeated bouts of infection or immunization. The genetic mechanism is somatic hypermutation
T-dependent Humoral Response
response of B cells to proteins depends on stimulation from Helper T Cells
T independent Humoral Response
response to polysaccharides and lipids
follicular B cells
reside in the follicles of lymphoid organs, T-dependent, class switched, and high affinity antibody maturation
Marginal-zone B cells
location: peripheral regions of splenic white pulp respond to blood-borne polysaccharide antigens
mostly IgM response
B-1 cells
respond to nonprotein antigens in mucosal tissues and peritoneum
mostly IgM response
primary response
usually lasts 5-10 days
IgM> IgG
lower affinity
secondary response
usually lasts 1-3 days
isotype switching, generally favors IgG
higher average affinity
Ig alpha and beta
proteins associated with membrane IgM and IgD receptors, help form the BCR copmlex
ITAMs in their cytoplasmic domain promote signal transduction after phosphorylation by Fyn, Lyn, and Blk
Syk
a tyrosine kinase analog of ZAP-70 that binds to phosphorylated ITAMs activate adaptor proteins
cross-linking
a key feature of B cell activation, when a single repeating antigen or multiple antigens bind one or more membrane receptor proteins
C3d-CR2
C3d complement coats pathogens. CR2 receptor expressed on B-cells binds C3d and strongly promotes signlaing
TLR
toll-like receptors, innate immune receptors expressed on a number of cells, including B cells, that promote immune reaction
Tfh
follicular Helper T cells
f(x): trigger formation of a germinal center
Helper T cells stimulated by B-cell antigen presentation mature in Tfh in lymph nodes.
germinal center reaction
B cell maturation in lymph nodes that involves isotype switching, somatic hypermutation, and production of memory cells
interfollicular regions
the region of lymph organs where B and T cells mix due to CCR7/ CXCR5 signaling
CCR7
a receptor that promotes migration toward T-cell rich regions
CXCR5
a receptor which promotes migration into B cell follicles
T-dependent B cells response: bidirectional interaction
- T and B cells are activated in different regions of the same lymphoid organ
- Chemokines signaling causes them to meet
i. chemokines induce B cells to express CXCR5 which promotes migration toward T cells
ii. chemokines induced T cells to produce CCR7 which promote migration toward B cells - B cell antigen presentation- b cells ingest protein antigens, present multiple fragment to T cells
- Key Event: Germinal Cell production
i. activated Helper T Cells express CD40L
ii. CD40L binds to CD40 on B lympohcytes
iii. signaling stimulates migration into nodes and activates germinal center reactions
ICOS
inducible costimulator, important for commitment of helper T cels to follicular helper cells
