T-cells and B-cells

CD3

a molecule made of 6 polypeptides associated with the TCR that transduces transmembrane signaling when the TCR is engaged which initiates the T-cell response

CD4

a single chain Ig supergene family that recognizes the nonpeptide binding domains of MHC II that synergize with TCR for T-cell activation

T-helper cells

cells that express CD4

CD8

a two chain cell surface molecule that is expressed by 1/3 of T cells and recognizes the nonpeptide binding portion of MHC I (pMHC I)

cytotoxic/suppressor T-cells

cells that express CD8

T-cell receptors

membrane bound receptors that are associated with CD3 and cannot bind to soluble epitopes, only epitopes presented in MHC molecules

complementarity-determining region (CDR)

the portion of the TCR formed by the variable domains that interacts with pMHC

TCR heterodimers

alpha-beta and gamma-delta

TCR DNA rearrangement

deletion, inversion, and junctional diversity

junctional diversity

the addition and removal of nucleotides by deoxynucleotidyl transferase (TdT)

chromosomes 14 and 7

the location of the TCR gene clusters

TCR light chains

alpha and gamma

TCR heavy chains

beta and delta

Rag-1 and Rag-2

the recombinases responsible for random rearrangement of VDJ genes in T-cells

MHC II antigen presentation

from dendrites and other phagocytes that use phagocytosis and micropinocytosis

found in ER and loads peptide once invariant chain is degraded

invariant chain

a molecule that prevents protein from loading in the ER, stabilizes MHC II and helps traffic MHC II to endocytic vesicles

MHC I antigen presentation

proteasome targets pathogens and generates peptides that are transported to the ER where it is loaded on MHC I and transported to Golgi and then cell surface

ubiquitin

a molecule used to target cytoplasmic proteins for destruction

TAP-1 and TAP-2

the proteins that transport peptides to the ER and facilitate loading of peptide onto MHC I

immunologic synapse

the interface between antigen presenting cells and naive T-cells

T-cell activation 1st signal

initiation of the immunologic synapse by the interaction of TCR with pMHC that sends a signal through CD3

T-cell activation 2nd signal

CD28 co-stimulates the TCR

ITAMs

molecules in CD3 that can transduce the signaling cascade

CD4+ T-cell maturation

driven by cytokine signals toward specific phenotypes

IL-2

acts as the 3rd signal in T-cell maturation by driving proliferation

IL-12 and IFN-y

drive Th0 to Th1 which responds to intracellular pathogens

IL-4 and IL-10

drive Th0 to Th2 which respond to extracellular pathogens and signal B-cells to become antibody-secreting plasma cells

Th0

activated naive T-helper cells

CD8+ T-cell maturation

immunologic synapse causes IL-2R expression which causes CD4+ to produce IL-2 which signals CD8+ into cytotoxic T lymphocytes

CTL products

perforin and granzyme

Tregs

CD4+ T cells that help regulate T-cell mediated immunity by controlling inflammation and preventing autoreactivity

memory T cells

CD4+ T cells engaged with CD28:CD80/86 that increase adhesion molecules and decrease CD62L

bound or soluble

the epitopes recognized by BCR

T-independent activation with TI-1

antigens activate B-cells through receptors other than BCR

LPS, B cell mitogens, antigen-specific B-cell activation

T-independent activation with TI-2

antigens crosslink BCRs to give the second signal which causes a cascade

T-cell dependent activation

specific epitope binds with BCR

CD4+ provides second signals

antigen phagocytosed and presented to T-cells on MHC II

agglutination

the crosslinking of antibodies with antigens that traps them and prevents mobility

neutralization

when antibody binding prevents interaction of microbial epitopes or soluble molecules from entering host cells

opsonization

the tagging of antigens with antibodies that facilitates phagocytosis

antibody-dependent cell-mediated cytotoxicity

the tagging of pathogens with antibodies that are susceptible to CTLs, eosinophils, and NK cells

immediate hypersensitivity

degranulation events triggered in response to IgE crosslinking on surface of mast cells and basophils

delayed-type hypersensitivity

activated Th1 move to site of infection and are reactivated by MHC II so they can activate macrophages that release cytokines, enzymes, and reactive oxygen species

FasL

a ligand on CTL that interacts with CD95 on target cells to induce apoptosis