Antigen-binding site, constant and variable region, CDR regions
How many polypeptide chains make up a TCR?
What characteristics does a TCR have?
all the TCR on the same cell are the same. each cell expresses a different TCR
Tc, TCL, CTL
cytotoxic t cell
What are the differences between TCR and BCR
TCR only has one binding site, they do not bind to soluble antigens, they have no rearrangement after antigen engagement, Matures in thymus, only used for recognition, no secreted receptor
How many CDR loops does a TCR have?
6 (3 on each chain)
What does TCR bind?
Calpha has how many options for rearrangment?
Cbeta has how many options for rearrangment?
what sections does the alpha chain have?
What sections does the beta chain have?
Where does rearrangment occur?
What is a RAG proteins?
recombination enzyme specific to T and B cells
What two parts make up a transposon?
Transposase (RAG) and Inverted repeates (RSS)
What are the functions of CD3 and zeta?
help transport the TCR to the cell surface and transmission of signal extracellular to intracellular
Severe combined immunodeficiency disease. people with SCID are susceptible to infections. lymphocyte profile (T- B- NK+), bone marrow transplant cna cure
RAG proteins have reduced activity. patient is T+ but low, B- NK+
CD3delta and CD3epsilon deficiency diseases
mutations in some CD3 genes. patient is either T+/TCR- or T- and B+ NK+
alpha:beta T cells make up how much of the population?
gamma:delta T cells make up how much of the population and where do they occur?
5%, predominate in epithelial tissue; recognize more than MHC-peptide complex
Which TCR genes are together on a locus and what does this mean?
delta and alpha chain genes share a locus meaning that if the alpha chain is rearranged then the delta chain cannot be made. This is the decision point for a t cell to become an alpha:beta or gamma:delta
antigen is broken up and brought to surface
MHC=peptide complex is displayed on the cell surface
Antigen Presenting Cell
cell with a surface MHC-peptide
super presenters that are leukocytes
What do t cells do after recognizing an antigen?
they induce changes in other cells
What do CD4 helper t cells do?
help other cells
What does Th1 do?
changes a macrophage
What does TH2 do?
changes a b cell or dendritic cell
What does CD8 CTL do?
kills other cells
What are CD4 and CD8?
co receptors that help bind to MHC I and MHC II
CD8 T CELL + virus infected cell =
dead virus infected cell
CD4 T cell + macrophage =
CD4 T cell + B cell =
How does MHC I display an antigen?
the pathogen replicates in the cell and proteins are degraded in the cytoplasm of the cell. peptides are then transported into the ER and bind to MHC I and then transported to the cell surface. MHC I expressing cells present to CD8 T cells. CD8 T cells (CTLS) kills the host cell using perforin and granzymes... NO ANTIBODIES
How does MHC II display an antigen?
Pathogen is recognized and internalized by a professional APC. Phagolysosomes degrade the protein into peptides. The peptide-MHC II complex is transported to the cell surface. Professional APC contacts CD4 T cells. CD$ Th cells secrete cytokines to signal B cell maturation...Antibodies needed (recognize pathogen on APC)
Which MHC binds to larger peptides?
What is peptide binding groove?
the binding spot on MHC binds to many different peptides that have similar features
What on MHC I does CD8 bind?
What on MHC II does CD4 bind?
What cells express MHC I?
most human cells
What cells express MHC II?
leukocytes and thymic stromal epithelial cells
increases expression of MHC I and II
DIfferent forms of one gene
different forms of one protein (isoforms)
Alternative forms of one gene (many alleles)
A few forms of one gene (few alleles)
same allele on both inherited chromosomes
different allele on both inherited chromosomes
HLA- A, B, C
present peptide antigens to CD8 t cells and interact with NK cells
HLA- E, G
interact with NK cells
HLA- DP, DQ, DR
present peptides to CD4 T cells
IFN- alpha, beta, gamma
increase expression of HLA class I heavy chain, B2 microglobulin, TAP, and proteasome subunits
increases expression of HLA class II
residues in the peptide that anchor it to the MHC
TCR recognizes the complex of both the peptide and MHC by interacting with exposed amino acid residues
How many peptide chains of MHC class II contribute to plymorphism?
How many peptide chains of MHC class I contribute to plymorphism?
Peptide binding motif
combination of anchor residues
favors multiple alleles
favors a single allele
the combination of alleles in a region of the chromosome
why do heterozygous individuals have an advantage over homozygous individuals?