Unit 4 - Immune System J Flashcards
Adaptive Immunity – Important Molecules
- Major Histocompatibility Complex (MHC-1 and MHC-2)
- T-cell receptors (TCRs)
- B-cell receptors (BCRs)
- Antibodies
Adaptive Immunity
Major Histocompatibility Complex (MHC-1 and MHC-2)
membrane protein complexes that display antigen
- a fam of mem. protein complexes encoded by a specific set of genes
- 1 reason tissues cannot be transplanted from 1 person to another without 1st est. compatibility
MHC proteins
- are the primary tissue antigens that determine whether donated tissue is recog. as foreign by the recipient’s immune system
- are AKA HUMAN LEUKOCYTE ANTIGENS (HLA)
- a tissue graft or transplanted organ is more likely to be successful if donor & recipient share HLA antigen
Adaptive Immunity
Major Histocompatibility Complex (MHC-1 and MHC-2)
MHC-1 :
- found on nearly all nucleated cells.
- binds to CD8 protein receptors on cytotoxic T-cells.
- displays antigen that has epitope that binds to T-cell receptors (TCRs).
of cytotoxic T-cells - important for immune responses involving infected host/body cells
Adaptive Immunity
Major Histocompatibility Complex (MHC-1 and MHC-2)
MHC-2:
- found on ANTIGEN PRESENTING CELLS ONLY (macrophages, dendritic cells, B cells)
- binds to CD4 protein receptors on Helper T-cells.
- displays antigen that has epitope that binds to TCRs of Helper T-cells.
Adaptive Immunity
- T-cell receptors (TCRs)
- protein receptors on T lymphocytes that recognize and bind to antigen presented by MHCs
- unique for every antigen
(NOT antibodies - bind ONLY to MHC-antigen complexes on the surface of an antigen-presenting cell)
Adaptive Immunity
- B-cell receptors (BCRs)
- protein receptors on B lymphocytes (make antibodies) that recognize and bind to a specific antigen (e.g. antigen on MHC-II of antigen presenting cell)
- are essentially antibodies on the surface of B cells.
- proteins that comprise the variable region of the receptor have a high mutation rate, which gives many (milliions) of possibilities for receptor phenotypes.
- a group of B-cells with the same BCRs = clone
Clone
a group of B-cells with the same BCRs = clone
Adaptive Immunity
- B-cell receptors (BCRs)
In order for an immune response to occur the appropriate clone for the antigen must be selected and then it must undergo expansion (proliferation) to produce plasma cells and memory B cells.
This process involves:
- recognition (binding) of antigen by the BCRs (very specific –
“lock and key”) = CLONAL SELECTION - activation of B-cells after recognition (via Helper T cells)
- proliferation (mitosis) that produces CLONAL EXPANSION
Recognition (binding) of antigen by the BCRs (very specific –
“lock and key”) =
clonal selection
Proliferation (mitosis) that produces…
clonal expansion
Adaptive Immunity
- Antibodies
- proteins that bind antigens & make them more visible to the immune system
- B lymphocytes make antibodies
antigen recognition molecules (proteins – gamma globulins)
B lymphocytes make _____
antibodies
Adaptive Immunity
- Antibodies
Structure:
4 polypeptide chains in a Y shape (arms contain the ANTIGEN-BINDING SITES)
- HINGE REGION b/t arms & stem allows flexible positioning of the arms as the antibody binds to the antigen
a. Fab – arms of Y; variable region, each arm can bind to one antigen two antigens total). Each arm consists of one light chain, one heavy chain. Chains are variable between antibodies, which gives them their specificity.
b. Fc region – stem of Y; constant region that determines antibody class. Binds to immune cells.
Fab
arms of Y; variable region, each arm can bind to one antigen two antigens total). Each arm consists of one light chain, one heavy chain. Chains are variable between antibodies, which gives them their specificity.
