Humoral Immune Response Flashcards
Describe the overall path of a B-cell.
Immature B-cells are created in the Bone Marrow (displays IgM). Leaves BM and circulates. As it laves it displays IgD + IgM = Naive B cell
In the primary follicle, Naive B cell endocytoses and presents Ag and becomes activated by 2nd signal from conjugate Th1 cell. Inactived B-cell die
Activated Bs travel to dark zone of germinal centers in 2ary follicles, express less Ig and undergo proliferation and somatic hypermutation –> centroblasts. Class switching can occur during proliferation
Centroblasts become centrocytes in Basal light zone where they are exposed to Ag by FDCs. Those with low affinity to Ag destroyed. Survivors go to Apical light zone and present Ag on MHC2 to Th. Recognized cells receive signals to differentiate into memory or plasma cells. Abs secreted by plasma cells bind to Ag and opsonize pathogen or neutralize virus. Phagocyte engulfs.
What is on the surface of resting mature naive B-cells?
BCR: IgM, IgD, Iga/B (signaling)
Co-BCR: CD19, CD81, CR2 (CD21) - complement receptor
MHC Class 2
CD40, CD45R(A), CD20
There are 2 types of B-cells. What are they?
B2 cells = Follicular, recirculating, majority
B1 cells = Marginal in spleen, reside in MALT (mucosal) in secondary lymphoid tissue
Describe the migration of Naive B cells.
Travel to secondary lymphoid tissue, enter thru HEV
When there is no Ag, they use the CXCR5 to migrate to the primary lymphoid follicle (inactive)
They receive survival signals from follicular DCs and exit through efferent lymphatic vessel.
