1-T Lymphocytes Flashcards
general characteristics
-subset of lymphocyte family with B cells and NK cells
-cannot be distinguished from B cells morphologically
-only recognize antigen with APC and MHC unlike B cells
ontogeny
aka where they come from
- prothymocytes from bone marrow
- thymus for maturation
- peripheral lymphoid organs
- blood stream until directed for cell mediated immune response
T helper lymphocytes aka CD4 subsets
- TH1 = cell mediated immunity (macrophages, IgG syn)
- TH2 = humoral immunity (mast cells, eosinophils, IgE syn)
- TH17 = enhances inflammation
- TFH = promote proliferating B cells/germinal centers in lymphoid organs
cytotoxic T lymphocytes
aka CTLs/CD8
lyse virus infected cells
regulatory T lymphocytes
aka CD4 or Treg cells
downregulate immunity
T cell antigen receptor
sites for antigen peptide residue + MHC residue
-30,000 identical copies of TCR in T cell surface
TCR structure
heterodimer of disulfide linked alpha/beta chains
-each chain has constant and variable region but only 1 antigen binding site
cytoplasmic tails not long enough to act as signal transducer across plasma membrane
CD3
required for signal transduction of T cells so expressed on every T cell but dont have anything to do antigens
made of invariant polypeptides (1 gamma + 1 delta + 2 epsilon + 2 zeta)
phosphorylation site on cytoplasmic tail for signals
co stimulatory molecules
TCR
- CD28 on T cell binds B7 on APC
- CD40L on T cell binds CD40 on APC
B7 and CD40 expressed on all professional APCs
end goal to enhance T cell proliferation ‘build army before attacking antigen’
CD4 accessory protein
transmembrane glycoprotein of single polypeptide on majority of mature T cells
-small quantities on surface of macrophages
most CD4 expressing lymphocytes are T helper cells
CD4 function
- cell adhesion
- signal transduction
- restricts T cell response to class II MHC
CD8 accessory protein
homodimer or heterodimer with alpha/beta chains
most CD8 expressing lymphocytes are cytotoxic T lymphocytes (CTLs)
CD8 functions
- cell adhesion
- signal transduction
- restrict T cell resp to class I MHC
signal transduction pathway
- binding of TCR to MHC to initate activate T cells
- early activation- PKC and other kinases activated to phos transcription factors
- gene transcription- AP 1 initiates IL-2 cytokine production
- mitosis- expand antigen specific clones to amplify immune response
TH1 development
- IL-12 from inflamm develop naive T cells
- interferon gamma IFN-y directs toward cell mediated immunity with active macrophages and CTLs
-CTL differentation via CD4 helper T cells producing cytokines and enhancing APC ability to stimulate differentiation
IFN-y most potent activator of macrophages