Lecture 7 Flashcards
how do you make a monoclonal antibody?
a mouse is injected with Ag that has multiple epitopes, spleen cells are isolated, then fused with myeloma cells, the resulting hybridomas are selected for the specific Ab’s they secrete, those are then cloned
how do you make polyclonal antibodies?
inject a mouse with Ag containing multiple epitopes, isolate the serum, and the result is a polyclonal antiserum
what are 3 defining characteristics of BCRs?
- are secreted or membrane bound
- bind to intact molecules
- can recognize proteins, lipids, adn carbs
what are 2 defining characteristics of TCRs?
- membrane bound ONLY
- bind only to peptide Ag bound to MHC
describe the structure of a T Cell Receptor?
αβ heterodimer with only one Ag binding site
why does the RAG enzyme go through two cycles to produce a T-cell receptor protein?
because both the α-chain locus and the β-chain locus must undergo recombination from germline DNA
how many proteins is CD3 made of?
3
what is CD3 important for?
signal transduction
what are the 2 classes of T cell receptors?
α:β or γ:δ
what are characteristics of α:β TCR’s?
high specificity, “signature” molecule of adaptive immune response, binds Ag presented by MHC I or II
what are the characteristics of γ:δ TCR’s?
recognize classes of Ag present on groups of pathogens, functions more in innate immune response, NOT associated with MHC
organization of TCR genes are very similar to what other genes?
imunoglobulin genes
how does the mechanism of TCR rearrangement occur?
RAG recognizes RSS, 1/2 the recombinase recognizes RSS and VJ and VDJ joining, circular excision products are made by looping out and deletion during rearrangement
what does SCID stand for?
severe combined immunodeficiency
what causes SCID?
a mutation in RAG genes
what is the result of the RAG gene mutation?
no functional B or T lymphocytes, no TCR excision circles
MHC class I binds peptides recognized by what?
CD8 T cells
MHC class I is expressed on what type of cell?
almost all somatic
what does MHC class I function in?
pathogen surveillance and killing somatic cells
MHC class II binds peptides recognized by what?
CD4 T cells
what types of cells is MHC class II expressed on?
dendritic cells, macrophages, B cells
what do MHC class II function in?
activating helper T cells
give a brief explanation of Ag processing and presentation.
a pathogen protein enters the cell, the protein is broken down and Ag is processed, Ag binds to an MHC molecule on the membrane of the cell and is presented to a TCR
what is the difference in MHC class I and MHC class II structure?
MHCI has an α and β chain whereas MHCII has two α chains
