B cell activation Flashcards
(39 cards)
Primary immune responses occur
in secondary lymphoid tissues
B cell activation is initiated
in the outer areas of follicles in primary immune responses
antigen crosslinks
to mIG on b cell which upregulates BR3
antigen mIG complex is
endocytosed and undergoes peptide MHC class II expression on B cell surface
BR3 interaction with Blys is
critical for survival of the B cell because it escapes apoptosis
B cell receptors that interact with T cell
HLA class II/peptide, HLA class II, B7-1(CD80) B7-1 (CD86), LFA-3 ICAM-1,2, CD40 L
T cell receptors that interact with B cells
TCR, CD4, CD28 CD2, LFA-1, CD 154
Hyper IgM syndrome
patient only has IgM
Thp in interfollecular region leads to
Th1 and Th2 cells, Cd40 L is expressed and sytokines secreted
Cognate interaction is
the acrtivation of B cells by way of all the receptors.
after dissassociation of B cells and T cells
the B cells clonally expand
Some B cells turn into
plasma cells that secrete IgM for 4 days post immunization
Other B cells do
isotype switch 10-14 dyas post immunization
plasma cells secrete
higher affinity antibodies
some B cells become
long lived memory B cells that ciruclate in immunosurveillance
down regulation of B cells and Plasma cells happens when
IgG’s bind low affinity Fc-Gamma Rs on B cells and plasma cells and they eventually undergo apoptosis
BR3 is upregulated on B cells following
antigen crosslinking of B cells mIg
BLyS is produced by
activated monocytes, macrophates, and dendritic cells
BLyS release is triggered by
cytokine acting on the cells or by IgG-FcGamma R signallng
BLyS binds to BR3 and leads to
B cell survival
abnormal production of BLyS allows
survival of autoreactive b cells
high serum levels of BlyS have been reported in
patients with rheumatoid arthiritis, SLE and multiple sclerosis
Typically proteins, B cell activation requires
CD4+ T cell cytokines and cognate interaction
Haptens are
often chemical or degradation products less than 5kD
