Immune Recognition II: Adaptive Receptors

Question 1

what are the three types of adaptive receptors?

Answer 1

immunoglobulins
t cell receptors
antigen presenting molecules

Question 2

immunoglobulins: what produces them, transmembrane/secreted?, what Ag do they recognize?

Answer 2

B cells

transmembrane (B cell receptors) or secreted (immunoglobulins or Ab)

3D surface of proteins, lipids, sugars, nucleic acids, mixture

Question 3

T cell receptors: what produces them, transmembrane/secreted?, what Ag do they recognize?

Answer 3

T cells

transmembrane

linear fragments of proteins presented on surface of APC

Question 4

antigen presenting molecules: what produces them, transmembrane/secreted?, what Ag do they recognize?

Answer 4

APC (dendritic cells)

transmembrane

bind peptides and present them at cell surface via MHC or HLA molecules for recognition by TCR

Question 5

Describe recombination with respect to Ag receptor synthesis/variability.

Answer 5

Different V, D, and J regions are combined and random nucleotides are introduced or changed at the junctions between the segments

the variable region is combined with a constant gene segment (maintain signal transduction/effector fxns)

Question 6

Give the general structure of immunoglobulins

Answer 6

heavy and light chain with variable and constant region

light+heavy heterodimer (disulfided linked) joins to another to form a homodimer (disulfide linked)

can be soluble or have a transmembrane/cytoplasmic domain

Question 7

what is the Ag binding site?

Answer 7

light chain domain+heavy chain domain

so two identical Ag binding sites on one immunoglobulin

Question 8

What does the constant region do?

Answer 8

support Ag binding site

provide interchain disulfide bonds

hinge region allows flexability

Fc fragment has effector fxns, sites for association w/ other molecules for transmission of signals after Ag recognition

Question 9

What are the five classes of Immunoglobulin isotypes

Answer 9

IgD
IgG
IgE
IgA
IgM

Question 10

Distinguish between the Ig isotypes based off structure

Answer 10

IgD - membrane bound
IgG - three heavy domains
IgE - four heavy domains
IgA - a dimer of two Ig
IgM - pentamer of 5 Ig

Question 11

What are different effector functions of Ig isotypes?

Answer 11

neutralization (block viral particles or toxins from acting)

opsonization (promote phagocytosis)

complement fixation (leading to C3 cleavage)

The Fc region imparts the effector fxn

Activate Fc receptor+ cells (NK, mast) to to respond (cytolysis, histamine release)

Question 12

Describe general TCR structure

Answer 12

heterodimers (alpha/beta or gamma/delta)

chains linked via disulfide bond

variable and constant domain

always membrane bound

Question 13

What types of Ag do TCRs recognize?

Answer 13

linear peptide of 8-16 polypeptides presented by MHC

recognizes both the peptide and the MHC 3D surface

Question 14

what is the CD3 complex?

Answer 14

TCR are always expressed at surface with 4 other transmembrane proteins

fxn - aids in activating intracellular signaling cascades

Question 15

does BCR act alone?

Answer 15

No.

Igbeta and Igalpha are two signaling subunits associated with Ig.

Question 16

does a single receptor binding lead to signal transduction?

Answer 16

No.

Ag binding brings brings BCR and TCR together in clusters on cell surface leading to actiavtion of cytoplasmic signaling cascades that lead to translocation of trxn factors to nucleus

Question 17

what expresses MHC I

Answer 17

all cells except RBC and neurons

Question 18

what expresses MHC II

Answer 18

only those that interact with T cells

dendritic cells, macrophages, monocytes, B cells

Question 19

what is the fxn of MHC molecules?

Answer 19

bind peptide fragments and present them on surface of APCs for T cells to recognize

Question 20

MHC I/II vs. intracellular/extracellular

Answer 20

MHC I = intracellular pathogen source

MHC II = extracellular pathogen source

Question 21

match up the CD4/8 to the MHC I/II

Answer 21

CD4+ T cells are MHC II restricted

CD8+ T cells are MHC I restricted

Question 22

Each individual has multiple HLA genes and there are hundreds of different alleles in the population. What two things does this have an impact on?

Answer 22

1. Transplantation

2. Disease resistance and susceptibility