forms a complex with membrane-bound MHC molecules on another host-derived cell.

is internalized by T cells via phagocytosis and subsequently binds to T-cell receptors in the endoplasmic reticulum

is presented on the surface of a B cell on membrane-bound immunoglobulins

bears epitopes derived from proteins, carbohydrates, and lipids

The highly variable CDR loops are located across the top surface.

The membrane-proximal domains consist of Cα and Cβ.

The portion that makes physical contact with the ligand comprises Vβ and Cβ, the domains farthest
from the T-cell membrane.

The transmembrane regions span the plasma membrane of the T cell.

The cytoplasmic tails of the T-cell receptor α and β chains are very short

alternative splicing to produce a secreted form of the T-cell receptor

alternative splicing to produce different isoforms of the T-cell receptor

isotype switching

somatic hypermutation

somatic recombination

are functionally similar

do not contain D segments

are more numerous

are encoded on a different chromosome from the variable β-chain gene segments of the T-cell
receptor

do not encode a transmembrane region

possess non-templated P and N nucleotides

A bright red, scaly rash is due to a chronic inflammatory condition.

Affected individuals are susceptible to infections with opportunistic pathogens.

It is invariably fatal unless the immune system is rendered competent through a bone marrow
transplant.

It is the consequence of complete loss of RAG function.

There is a deficiency of functional B and T cells.

It is associated with missense mutations of RAG genes.

they are more abundant in tissue than in the circulation

the δ chain is the counterpart to the β chain in α:β T-cell receptors because it contains V, D, and J segments in the variable region

they share some properties with NK cells

activation is not always dependent on recognition of a peptide:MHC molecule complex

expression on the cell surface is not dependent on the CD3 complex

α

β

γ

δ

ε

endocytosis

promiscuous processing

antigen processing

antigen presentation

peptide loading

CD3

MHC molecules

T-cell receptor α chains

γ:δ T cells

β2-microblobulin

Nucleus

Golgi apparatus

endoplasmic reticulum

exocytic vesicles

lysosomes

They make up about 1% of cellular protein.

They consist of four rings of seven polypeptide subunits that exist in alternative forms.

They are produced in response to IFN-γ produced during innate immune responses.

They produce a higher proportion of peptides containing acidic amino acids at the carboxy terminus
compared with constitutive proteasomes.

They contain 20S proteasome-activation complexes on the caps.

TAP is a homodimer composed of two identical subunits.

TAP transports proteasome-derived peptides from the cytosol directly to the lumen of the Golgi
apparatus.

TAP is an ATP-dependent, membrane-bound transporter.

Peptides transported by TAP bind preferentially to MHC class II molecules.

TAP deficiency causes a type of bare lymphocytes syndrome resulting in severely depleted levels of
MHC class II molecules on the surface of antigen-presenting cells.

tapasin

calnexin

calreticulin

ERp57

β2-microglobulin

Tapasin is an antagonist of HLA-DM and causes more significant increases in MHC class I than MHC
class II on the cell surface.

Tapasin is a lectin that binds to sugar residues on MHC class I molecules, T-cell receptors, and
immunoglobulins and retains them in the ER until their subunits have adopted the correct
conformation.

Tapasin is a thiol-reductase that protects the disulfide bonds of MHC class I molecules.

Tapasin participates in peptide editing by trimming the amino terminus of peptides to ensure that
the fit between peptide and MHC class II molecules is appropriate.

Tapasin is a bridging protein that binds to both TAP and MHC class I molecules and facilitates the selection of peptides that bind tightly to MHC class I molecules.

Somatic recombination of V, D, and J segments is responsible for the diversity of antigen-binding sites.

Somatic hypermutation changes the affinity of antigen-binding sites and contributes to further diversification.

Class switching enables a change in effector function.

The antigen receptor is composed of two identical heavy chains and two identical light chains.

Carbohydrate, lipid, and protein antigens are recognized and stimulate a response.

Vα and Cα

VβandCβ

CαandCβ

VαandCβ

Vα and Vβ

2

3

4

6

12

1;1

2;1

1;2

2;2

2;4

CD3γ

CD3δ

CD3ε

ζ

All of the above

peptides ranging between 8 and 25 amino acids in length

not requiring degradation for recognition

amino acid sequences not found in host proteins

primary, and not secondary, structure of protein

binding to major histocompatibility complex molecules on the surface of antigen-presenting cells.

When activated, CD8 T cells in turn activate B cells.

CD8 is also known as the CD8 T-cell co-receptor.

CD8 binds to MHC molecules at a site distinct from that bound by the T-cell receptor.

CD8 T cells kill pathogen-infected cells by inducing apoptosis.

CD8 T cells are MHC class I-restricted.

immunoglobulins

T-cell receptors

complement proteins

MHC class I or class II molecules

CD4.

α:β T-cell receptors recognize antigen only as a peptide bound to an MHC molecule.

αβ T-cell receptors recognize antigens in their native form.

α:β T-cell receptors, like B-cell immunoglobulins, can recognize carbohydrate, lipid, and protein
antigens.

Antigen processing occurs in extracellular spaces.

Like α:β T cells, γ:δ T cells are also restricted to the recognition of antigens presented by MHC
molecules.

carbohydrate:MHC complex

lipid:MHC complex

peptide:MHC complex

all of the above

none of the above

alpha (α) and beta (β); CD4

alpha (α) and beta2-microglobulin (β2m); CD4

alpha (α) and beta (β); CD8

alpha (α) and beta2-microglobulin β2m); CD8

alpha (α) and beta (β); γ:δ T cells

side chains of amino acids in the middle of the peptide

co-receptors CD4 or CD8

membrane-proximal domains of the MHC molecule

constant regions of antibody molecules

α helices of the MHC molecule

a particular MHC molecule has the potential to bind to different peptides

when MHC molecules bind to peptides, they are degraded

peptides bind with low affinity to MHC molecules

none of the above describes promiscuous binding specificity

all of the above describes promiscuous binding specificity

anchor residues

peptide-binding motif

variable amino acid residues on α helices of the MHC molecule

β2-microglobulin

invariant chain

viral antigens are presented by MHC class I molecules on the surface of a cell that is not actually infected by that particular virus, or peptides of nuclear or cytosolic proteins are presented by MHC class II molecules.

cytosol-derived peptides enter the endoplasmic reticulum and bind to MHC class II molecules

phagolysosome-derived peptides bind to MHC class II molecules

viral antigens are presented by MHC class II molecules on the surface of a cell that is not actually infected by that particular virus or peptides of nuclear or cytosolic proteins are presented by MHC class I molecules

phagolysosome-derived peptides bind to MHC class III molecules

The organization of the T-cell receptor antigen-binding site is distinct from the antigen-binding site of immunoglobulins.

The orientation between T-cell receptors and MHC class I molecules is different from that of MHC class II molecules.

The CDR3 loops of the T-cell receptor α and β chains form the periphery of the binding site making contact with the α helices of the MHC molecule.

The most variable part of the T-cell receptor is composed of the CD3 loops of both the α and β
chains.

All of the above statements are correct.

gene rearrangements similar to those observed in T-cell receptor genes

the existence of many similar genes encoding MHC molecules in the genome and extensive
polymorphism at many of the alleles

somatic hypermutation

limited polymorphism at many of the alleles

isotype switching

haplotype

allotype

isotype

autotype

HLA type

HLA-G α chain

HLA-DO β chain

HLA-DQ β chain

HLA-A α chain

HLA-DR α chain

HLA-A α chain

HLA-DO α chain

HLA-B α chain

HLA-DR β chain

HLA-C α chain

HLA-A

HLA-B

HLA-C

HLA-DP

HLA-DR

β2-microglobulin and invariant chain

HLA-G α chain

TAP-1

tapasin

HLA-DR α chain

isoform

isotype

oligomorph

allotype

haplotype

alleles; allotypes

anchor residues; peptide-binding motif

allotype; haplotypes

invariant chains; haplotypes

restriction residues; MHC allotype

all polymorphic alleles preserved in a population

T-cell receptor interaction with peptide:MHC complexes directed to a planar interface

a mechanism in T cells that is analogous to affinity maturation of immunoglobulins

selected alleles increase in frequency in a population

selection of most appropriate transplant donor directed at the identification of identical or similar
combinations of HLA alleles compared with the transplant recipient

transduce signals to the interior of the T cell correct

bind to antigen associated with MHC molecules

bind to MHC molecules

bind to CD4 or CD8 molecules

facilitate antigen processing of antigens that bind to the surface of T cells

lack of somatic recombination in T-cell receptor and immunoglobulin gene loci

lack of somatic recombination in T-cell receptor loci

lack of somatic recombination in immunoglobulin loci

lack of somatic hypermutation in T-cell receptor and immunoglobulin loci

lack of somatic hypermutation in T-cell receptor loci

HLA-DM

HLA-DO

HLA-DP

HLA-DQ

HLA-DR

bacterial; viral

dead; live

extracellular; intracellular

intracellular; extracellular

virulent; attenuated

plasma membrane →TAP1/2 →proteasome →MHC class I →endoplasmic reticulum

TAP1/2 →proteasome →MHC class I →endoplasmic reticulum→plasma membrane

proteasome →TAP1/2 →MHC class I →endoplasmic reticulum →plasma membrane

proteasome →TAP1/2 →endoplasmic reticulum →MHC class I →plasma membrane

endoplasmic reticulum →proteasome →MHC class I →TAP1/2 →plasma membrane

B cells are unable to develop

CD8 T cells cannot function

CD4 T cells cannot function

intracellular infections cannot be eradicated

peptides cannot be loaded onto MHC molecules in the lumen of the endoplasmic reticulum

protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →endocytosis →plasma membrane

endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II →plasma membranecorrect

removal of CLIP from MHC class II →binding of peptide to MHC class II →protease activity →endocytosis →plasma membrane

binding of peptide to MHC class II →endocytosis →removal of CLIP from MHC class II →protease activity →plasma membrane

plasma membrane →endocytosis →protease activity →removal of CLIP from MHC class II →binding of peptide to MHC class II

erythrocyte correct

hepatocyte

lymphocyte

dendritic cell

neutrophil

macrophage

neutrophil

B cell

dendritic cell

all of the above are professional antigen-presenting cells

peptide-binding motif: combination of anchor residues in a peptide capable of binding a particular
MHC haplotype

MHC restriction: specificity of T-cell receptor for a particular peptide:MHC molecule complex

balancing selection: maintenance of variety of MHC isoforms in a population

directional selection: replacement of older MHC isoforms with newer variants

interallelic conversion: recombination between two different genes in the same family

The greater number of HLA alleles provides a wider variety of HLA molecules for presenting HIV- derived peptides to CD8 T cells even if HIV mutates during the course of infection.

Heterozygotes have more opportunity for interallelic conversion and can therefore express larger numbers of MHC alleles.

Directional selection mechanisms favor heterozygotes and provide selective advantage to pathogen exposure.

As heterozygosity increases, so does the concentration of alloantibodies in the serum, some of which cross-react with and neutralize HIV

pre-B-cell receptor

BAFF receptor

CD34

CD4

membrane-bound stem-cell factor (SCF)

VDJ is successfully rearranged and mu heavy chain is made.

V–J is rearranging at the light-chain locus.

mu heavy chain and lambda or kappa light chain is made.

V is rearranging to DJ at the heavy-chain locus.

D–J is rearranging at the heavy-chain locus

The κ light-chain genes rearrange before the heavy-chain genes.

The κ light-chain genes rearrange before the λ light-chain genes.

The λ light-chain genes rearrange before the heavy-chain genes.

he λ light-chain genes rearrange before the κ light-chain genes.

The μ heavy-chain genes rearrange first and then the λ light-chain genes rearrange