Antigen Recognition by lymphocytes Flashcards
what cells synthesise and secrete immunoglobulins
B cells
what are cells of the same specificity called
clones
what are B cell receptors
cell-surface antibodies
which two types of cells are produced by lymphocytes in response to an antigen
effector cells
memory cells
why are helper t cells necessary for antibody responses
without them only IgM antibodies are produced and in small amounts
what structure are TCRs structurally related to
immunoglobulin Fab region
(makes sense - need to be just as specific)
how many TCRs are on the surface of each T cell
are they all identical
30,000 identical TCRs
what form of TCR do the majority of T cells have
what is its structure
alpha beta TCRs
alpha and beta chains with cytoplasmic tails and are linked by a disulphide bond
what form of TCR do the minority of T cells have
how is its structure different to the major one
gamma delta TCRs
structurally similar but made of different peptides
what structure in their variable domains allows TCRs to detect antigens
hypervariable loops/CDRs
how can antibodies and TCRs bind the same antigen at the same time
different regions of the same molecule (epitopes) are recognised by each
what does CD stand for in relation to lymphocytes
cluster of differentiation
what type of cells express CD3
all T cells
what type of cells express CD4
helper T cells
what type of cells express CD8
cytotoxic T cells
structure of CD4 and CD8
CD4: 4 extracellular immunoglobulin-like domains (D1, D2, D3, D4)
CD8: 2 extracellular immunoglobulin-like domains (alpha and beta) held together by disulphide bridge
what does the CD4 complex do at the TCR
simultaneously binds the same MHC class II
increases TCR sensitivity to antigen and cements binding
explain the role of LFA-1 and ICAM-1
accessory molecules
LFA-1: present on T cell
ICAM-1: present on antigen-presenting cell
adhesion molecules involved in initial contact of T cells and APCs.
TCR-MHC binding causes a conformational change, increasing affinity and prolonging cell-cell contact
what are the three kinds of signals APCs deliver to naive T cells
activation
survival
differentiation
what do helper T cells do in response to antigen binding
secrete cytokines which control and coordinate the immune response:
- macrophage activation
- B cell stimulation
what do lymphocytes do in response to antigen binding (general)
divide to form clones of antigen-specific cells
role of plasma cells
antibody secretion
