University:
York University
Course:
SC/BIOL 3120 | Immunobiology
Academic year:

2023
Views:

459

Pages:

2
Author:

Niklas

Antigen Binding to BCR: Leads to B-cell signal transduction cascade C3d complement fragment that acts as an opsonant C3d opsinization "make foreign matter easily phagocytized" CD21 BCR BCR is non-covalently linked to 3 co-stimulatory molecules CD01 (TAPA-1) CD11 CD19 Signal propagation along the membrane moves signal from outside to inside the cell! CD21 CD1 ITAM the cytoplasmic tail of the BCR is very short (3 amino acids) which means that it cannot relay signals to the cell's interior on its own (CD795) BCR is non-covalently associated with: Igd ITAMS phosphorylated by Src Kinases ITAMS (immunoreceptor tyrosine activation motif): tyrosines are VERY easily phosphorylated adaptor proteins that act as really good docks for other proteins to bind results in formation of signalsome cytoplasmic signaling complex When an infection occurs, there is a lot of antigen around. Enough antigen to bind TCR and BCR independently. This takes time because initial contact with antigen by TCR/BCR is random. There are millions of different B and T-cells, each with their own specificities. BCRs and TCRs do not have the same amino acid sequence, but there are enough BCRs and TCRs produced that one of each will recognize the antigen. Most antigens have multiple epitopes. It is likely there are several immune responses going on at the same time, each against a different epitope. T-cells recognize antigen only when processed/presented by self MHC. T-cells are MHC restricted. B-cells can recognize unprocessed/unpresented antigen. B-cells are not MHC restricted. B-cells can also recognize antigen that is presented by other APCs in the lymph node. B-cell Response: What is required for a good B-cell response: Antigen B-cell Activated CD4+ T-cell A lot of the antigen that arrives at the lymph node has been opsonized by complement, so that it is more easily seen by B-cells. Antigen flows through FRCC (fibroblastic reticular cell conduit system), a highway for antigen. B-cells can grab antigen from FRCC by the basement membrane.