Antigen Recognition by lymphocytes

Question 1

what cells synthesise and secrete immunoglobulins

Answer 1

B cells

Question 2

what are cells of the same specificity called

Answer 2

clones

Question 3

what are B cell receptors

Answer 3

cell-surface antibodies

Question 4

which two types of cells are produced by lymphocytes in response to an antigen

Answer 4

effector cells
memory cells

Question 5

why are helper t cells necessary for antibody responses

Answer 5

without them only IgM antibodies are produced and in small amounts

Question 6

what structure are TCRs structurally related to

Answer 6

immunoglobulin Fab region
(makes sense - need to be just as specific)

Question 7

how many TCRs are on the surface of each T cell
are they all identical

Answer 7

30,000 identical TCRs

Question 8

what form of TCR do the majority of T cells have
what is its structure

Answer 8

alpha beta TCRs
alpha and beta chains with cytoplasmic tails and are linked by a disulphide bond

Question 9

what form of TCR do the minority of T cells have
how is its structure different to the major one

Answer 9

gamma delta TCRs
structurally similar but made of different peptides

Question 10

what structure in their variable domains allows TCRs to detect antigens

Answer 10

hypervariable loops/CDRs

Question 11

how can antibodies and TCRs bind the same antigen at the same time

Answer 11

different regions of the same molecule (epitopes) are recognised by each

Question 12

what does CD stand for in relation to lymphocytes

Answer 12

cluster of differentiation

Question 13

what type of cells express CD3

Answer 13

all T cells

Question 14

what type of cells express CD4

Answer 14

helper T cells

Question 15

what type of cells express CD8

Answer 15

cytotoxic T cells

Question 16

structure of CD4 and CD8

Answer 16

CD4: 4 extracellular immunoglobulin-like domains (D1, D2, D3, D4)
CD8: 2 extracellular immunoglobulin-like domains (alpha and beta) held together by disulphide bridge

Question 17

what does the CD4 complex do at the TCR

Answer 17

simultaneously binds the same MHC class II
increases TCR sensitivity to antigen and cements binding

Question 18

explain the role of LFA-1 and ICAM-1

Answer 18

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

Question 19

what are the three kinds of signals APCs deliver to naive T cells

Answer 19

activation
survival
differentiation

Question 20

what do helper T cells do in response to antigen binding

Answer 20

secrete cytokines which control and coordinate the immune response:
- macrophage activation
- B cell stimulation

Question 21

what do lymphocytes do in response to antigen binding (general)

Answer 21

divide to form clones of antigen-specific cells

Question 22

role of plasma cells

Answer 22

antibody secretion