Pre-elearning IC2: T cells & B cells + MHC Flashcards
How does the adaptive immune system achieve broad coverage against different antigens with respect to the MHC molecules?
Different sets of MHC class I and II molecules can present different antigens to T cells as many genes code for the MHC molecule, ensuring that the adaptive immune response provide broad coverage.
How is the level of MHC molecule expression regulated?
Cytokines regulate expression of MHC I and II molecules. Interferons like IFNalpha and IFN gamma increase expression of MHC I/II molecules that helps activate appropriate t cells in times of infection.
What receptors are found on the CD8+ and CD4+ T cells?
CD8+ T cell: CD8 receptor and T cell receptor
CD4+ T cell: CD4 receptor and T cell receptor
In what cells are MHC class I molecules absent?
Red blood cells (no nucleus)
For MHC class I and MHC class II molecules, which bind to endogenous antigens and which bind to exogenous antigens?
Class I: endogenous (e.g. normal self antigen, viral components, neoantigens)
Class II: exogenous (e.g. foreign antigens belonging to invading pathogens)
How does the innate immune system activate the adaptive immune system?
Invading pathogens get recognised by an APC and gets engulfed by phagocytosis, where they get broken into antigenic fragments. Each MHC class II protein binds to an antigenic fragment and they get presented to helper T cell
What is the difference in the gene recombination at the constant region of antibodies and T cell receptors?
B cells undergo gene recombination at the constant region to give rise to different classes of antibodies but T cells do not undergo recombination in their constant region
Correct ans: The constant region of Fc domain of IgM undergoes gene rearrangement , subsequently the variable regions (VL & VH) of Fab region of IgG genese undergoes gene rearrangement
T cells do not undergo recombination at the constant region of TCR. TCR diversity lies in the V alpha and V beta regions of TCR
(atikah’s answer)
I don’t think Bcells undergo gene recombination at the constant region, gene rearrangement happens at the constant region in Fc domain of IgM (the first response antibody) that activated B cells secrete after encountering pathogenic antigens
What gene arrangements occur after IgM is secreted?
Mature B cells undergoes gene arrangement of constant regions so that they produce IgG instead of IgM. This is known as class switching. After that, there is gene rearrangement in the V regions in the light and heavy chains to have hypervariable CDR
(atikah)
Answer:Gene arrangement in the VL and VH regions of Fab domain of IgG
What is the first response antibody?
IgM
What are ITAMs and how many ITAMs do each TCR complex contain?
ITAMs are immunoreceptor-tyrosine based activation motification and there are 10 ITAMs in each TCR complex.
What does the alpha and beta chain in TCR associate with and why?
It associates with CD3 dimers as the cytoplasmic tail is too short
What is the difference between affinity and avidity?
Affinity: Strength of interaction between antibody and epitope at a single antigenic site
Avidity: Strength with which antibody binds to target. Multiple epitopes in the target
How does affinity relate to specificity and cross reactivity?
High affinity for an antigen relates to high specificity and low cross reactivity
How many CDRs are there in an antibody monomer and a T cell receptor?
Antibody monomer: 12 (3 on heavy chain and 3 on light chain, 2 Fab arms)
TCR: 6 (3 CDRs in each V alpha and V beta chain)
What does the Fc domain of the antibody bind to?
Fc receptors on effector cells (Macrophages, NK cells, neutrophils)
