BLD 434 Final Flashcards
(127 cards)
What is the general mechanism of somatic recombination
An enzymatic process that generates diversity of B and T cell receptors by RAG-1 & RAG-2 cutting gene segments and splicing them back together
What cells are involved in somatic recombination
B and T cells
What is the general mechanism of somatic hypermutation
Increased point mutations initiated by AID enzyme throughout the heavy and light chain V regions (not C regions)
What is accomplished in somatic recombination
isotype switching that changes antibody function
What cells are involved in somatic hypermutation
B cells
What is accomplished in somatic hypermutation
generates antibody diversity
What is the general mechanism of isotype switching
When activated B cells encounter specific signaling molecules via their CD40 receptors they undergo antibody class switching, the constant region of the heavy chain is changed, variable region stays the same
What is accomplished with isotype switching
changing a B cell’s production of antibody from one class to another
What cells are involved in isotype switching
Naive B cells
What is the goal of positive selection
Ensures only useful T cells that are able to bind MHC are released to the periphery
Where does positive selection occur
Inner cortex in the thymus
How does positive selection occur
selects for developing T cells with receptors that recognize peptide antigens presented by self MHC (Double positive thymocytes undergo + selection)
What cells are involved in positive selection
alpha-beta T cells
What is the goal of negative selection
Weeds out cells that are reactive/bind too tightly to self antigens because they can harm our body
What cells are involved in negative selection
B and T lymphocytes
Where does negative selection occur
Medulla
How does negative selection occur
T cells that bind too avidly to self antigen presented by DC or macrophages are deleted by apoptosis
What is the “two signal hypothesis”
A T cell must receive a minimum of two signals to respond to an antigen
What cells, receptors/ligands are involved in the two signal hypothesis
- primary signal through TCR binding cognate peptide/ MHC I or II
- A co-stimulatory signal through co-stimulator molecules on APC
List the surface proteins of naive T cell and APC
on surface of naive T cell: CD28 & TCR
on surface of APC: MHC II & B7
What would happen if the two signal hypothesis was not satisfied
It will prevent new naive T cells from joining the fight because they cannot receive their second signal
What is linked recognition
when an antigen is processed and presented by the B cell to the Tfh cell, in order for B cell to become activated
What are the cells, receptors/ligands involved in linked recognition
CD40 and CD40L
What is the outcome of linked recognition
T cell help for B lymphocytes to activate isotype switching and somatic hypermutation
(T dependent Ab responses)
