Antigen Recognition by T Cells

surface, secreted

Antigen Receptors are found ONLY on the __ of T cells

• Not __ like B cell antibodies

Protein antigens, free antigen

• T cells can only recognize __ __ - short chains of amino acids (no lipids/nucleic acids, etc)

  • can NOT recognize “__ __”

MHC Restriction

T cells only recognize peptide antigens when bound to MHC Rs found on surface of self cells

MHC, same

For T cells:

• Antigen must be “processed and presented” on a __ by another cell from __ (same/different) individual

mature, naive, activated, one, DNA rearrangement

T cells and TCR

• Expressed on cell surface of __, __, __ T cells in blood/tissues

• T cells are “clonal” and can only recognize __ antigen (just like B cells)

• TCR coding sequence is produced by __ __ during T cell development in bone marrow and thymus

Cell-membrane, variable, constant, immunoglobulin

TCR structure

• Only exists as a __-__ associated receptor protein, bound to membrane

• Receptor protein with __ and __ regions

  • Domain structure also composed of __ domains

alpha, beta, antigen

Major T receptor has 2 polypeptide chains (__ and __)

• Both of these chain domains required for __ specificity

antigen-binding, combined variable

• Variable regions interact to form single __ binding site

  • 3 hypervariable regions in __ __ domains

Gene segments, re-arrangement, antibody, binding

Genetics of TCR

• Coded in germline as __ __

• DNA __ __ during differentiation of each individual T cell

• Production of unique __ → Allows high diversity of TCR antigen __ sequence

RAG proteins, TdT

TCR gene rearrangement

• Combinatorial diversity via __ __ and Junctional diversity via __

multiple C, alpha, beta, splicing, diversity

TCR vs Ig gene rearrangement

• NO __ __ region gene segments, only 1 __ and 1 __

• C region added by __, NOT DNA recombination

• NO somatic hypermutation for __ mechanism

  • *TCRs are ok with just binding to MHC
    doesn't wanna mess with that

TCR Co-receptors

Proteins found next to TCR on T cell surface for aiding signaling

Invariant, antigen-specific

TCR Co-receptors are ___! (variant/invariant)

• Meaning NOT __-__ / don’t bind to antigen

CD3

Present on ALL T cells, bring TCR to cell surface

Epsilon, delta, gamma

Peptide chains responsible for expression of TCR on cell surface (CD3)

Zeta

Peptide chain for signal transduction of TCR (CD3)

CD4

Co-receptor for MHC class II recognition

CD8

Co-receptor for MHC class I recognition

CD4, CD8

Mature T cells have EITHER __ or __ associated with their TCR

Peptide antigen

__ __ …must be produced within self cells by breakdown of proteins (for MHC bind)

MHC Proteins

Cell-surface proteins attached to cell membrane via transmembrane region and cytoplasmic “anchor”

antigen, T, co-dominant, alpha, beta

MHC Proteins

• Present __ to _ cells and recognized by TCR

• Genes for MHCs are inherited as ____ alleles (no DNA recombination)

• Have polypeptide chains __ and __ that are NOT the same as chains of TCRs

2, immunoglobulin

MHC Structure - Made of _ polypeptide chains

• ALL of polypeptide chains contain multiple __-like domains

MHC I

Present internal peptide antigens from within the cell (i.e. viral proteins)

(MHC I or II)

high, no, nucleated somatic, co-dominantly

MHC I

• Alpha chain - Polypeptide chain with __ degree of allelic variation

• Beta-2 macroglobulin - Small protein with __ degree of allelic variation

• Expressed on ALL __ __ cells

• All alleles __-__ expressed, mostly heterozygous

MHC II

Present external peptide antigens (those taken from phagocytosis)

(MHC I or II)

High, high, professional APCs, co-dominantly

MHC II

• Alpha chain - Polypeptide chain with __ degree of allelic variation

• Beta chain - Polypeptide chain with __ degree of allelic variation

• Expressed on __ ___

• All alleles __-__ expressed, mostly heterozygous

MHC I Peptide length

8-10 amino acids long

MHC II Peptide length

13-25 amino acids long

Non-covalent

Peptide binding to MHC Class I and II

• Interaction by __-__ bonds