Test 1, deck 3 Flashcards
(41 cards)
3 types of B cells
conventional B2 cell
innate-like B1 cell
innate-like marginal B cell
what are B1s directed against? where are they made? where are they found? what are 3 other important distinguishing characteristics
- directed against carbs
- made in fetal liver- live forever
- found in peritoneal & pleural cavities
1) no isotype switch
2) no somatic hypermutation
3) no memory
4 factors that influence immunogenicity
1) larger antigen
2) route of injection- subcutaneous
3) particulates are better
4) attached to adjuvant
what is an adjuvant?
a substance that enhances the body’s immune response to an antigen- e.g. Alum
important components of B-cell activation when they’re T-cell dependent
- need 2 signals after antigen binds BCR, and is presented in MHC class II
1) interaction of TCR with MHC/peptide complex
2) costimulatory molecules 40/40L
what happens with the activation of T cells in the presence of antigen-bound B cells?
T cells secrete cytokines (4, 5, 6) drive b-cells into proliferation, then differentiation as memory cells & plasma cells
where do B cells proliferate?
in germinal centers (sites within 2* lymphoid organs- lymph nodes & spleen)
T/F B and T cells recognize the same antigen
TRUE- but not the same epitope
primary vs secondary activation
primary- slow- IgM
secondary- fast- IgG
how does affinity increase?
increases as a result of somatic hypermutation at the end of primary response
what is the enzyme required for isotype switch?
AID (activation-induced cytidine deaminase)
when and where does isotype switch occur?
occurs in T-cell dependent responses, is regulated by T-cell cytokines; is in germinal center in 2ndary lymphoid tissues
where do VDJ rearrangements occur?
bone marrow & thymus (primary lymphoid tissues)
what 3 things happen in germinal centers?
- B cell proliferation & differentiation **
- somatic hypermutation
- class switch
- determination of memory vs. plasma
where in the germinal center does hypermutation occur?
dark zone
where in the germinal center are bad hypermutations recognized?
light zone
after hypermutation, cells with high affinity for foreign antigens are rescued from cell death by
follicular dendritic cells with bound antigen
T/F You see a higher rate of antibodies with somatic mutations in T-independent antigens
FALSE- consequently, lower affinity
what does the t-independent activation of b cells normally respond to
bacterial polysaccharide antigens which can be cross-linked (little memory)
what does the t-independent activation of b cells normally respond to
bacterial polysaccharide antigens which can be cross-linked (little memory)
what is immunological tolerance?
non-responsiveness to specific antigens (NOT immunosupression)
what are some examples of tolerance?
- antigens from self tissues
- food
- commensal bacterium
- pregnancy
3 mechanisms of peripheral tolerance
1) regulatory t cells
2) myeloid derived suppressor cells (MDSCs)
3) clonal anergy
how are non-thymic self-antigen reactive cells eliminated?
AIRE induces expression of wide range of genes expressed in other organs- e.g. endocrine gland
