Definitions (2) Flashcards
T-cell antigen receptor
transmembrane protein
2 chains (alpha & beta) form one antigen binding site
antigen binding takes place at the amino terminal variable sequence
immunoglobulin
either a surface molecule on B cells (B-cell antigen receptor) w/ a transmembrane region or a free-floating protein w/ a dif C-terminus
2 heavy chains & 2 light chains in one unit (H2L2)
antigen binding takes place at the amino terminal variable sequence
epitopes
regions of the overall antigenic substance that can bind to the TCR or BCR
what antigenic receptors “see”
haptens
small molecules that can bind to larger substances & react w/ specific TCRs or BCRs to elicit an immune response
ex. penicillin - hapten that causes allergies
multiple myeloma
excess soluble Ig molecules
tumor of one B cell producing one Ig (monoclonal)
Fab vs. Fc antigen regions
Fab: varied from patient to patient & bound antigen, shows lots of variability in amino acid sequence b/n patients, contain hypervariable amino acid sequences at the complementarity determining regions
Fc: constant in amino acid sequence, don’t bind antigen
TH1 vs. TH2 responses
TH1: killer cells kill virus infected cells, activated macrophages keep intracellular mycobacteria in check, or complement-activating antibodies opsonize microbes
TH2: T cells generate antibodies to neutralize a toxin or block a microbe’s adhesion molecules
granulomas
millions of macrophages & T cells
whenever a microbe leaves a macrophage, nearby macrophages phagocytose the microbe & respond w/ a burst of cytokine release
intracellular microbes can be kept under control in the granuloma
how viruses interfere w/ antigen presentation:
herpes simplex
CMV
EBV
herpes simplex: inhibition of TAP-mediated transport of peptides into the ER
CMV: removal of MHC class I molecules from the ER
EBV: inhibition of proteasomal activity, simulates infected cells to produce IL-10 (a suppressive cytokine)
intra-epithelial lymphocytes
gamma-delta T cells & NKT cells present in mucosal membranes (in the gut mucosa b/n the epithelial cells)
their TCRs recognize lipid antigens presented by the MHC-like CD1d molecule
antibody-dependent cellular cytotoxicity
NK cells can bind the Fc portion of antibodies via their CD16 receptor
if antibody binds to the surface of a cell,t he NK cells can bind teh Fc part of the antibody
if several CD16 receptors are engaged by bound antibody, the NK cells kill the antibody-coated cell
