Immunology Lecture 11. Flashcards
What is tolerance?
lack of response to a specific antigen
What can tolerance involve?
elimination, neutralization, generation of unique cell populations
Why is tolerance important?
potential for auto reactivity with induce rearrangements in V regions of T and B cells - failure for tolerance makes autoimmune diseases
What type of cell expresses AIRE?
medullary epithelial cell in the thymus
What are the two major mechanisms of tolerance induction?
deletion or reactive cells or ANERGY
What does lack of second signal cause? What is the second signal in T cells?
ANERGY CD28/B7
What are T regulatory cell markers?
FOXP3+, CD25+, CD4
TGF-B
induces T regulatory cells
IL-10
produce immune dampening
IPEX
the result of no FOXP3 = enteropathy, diabetes, thyroiditis, dermatitis
Why are tumor cells not killed by the immune system?
cancer cells produce TGF-B which induce T regulatory cells, T regulatory cells release IL-10, no stimulation of cytotoxic T cells happens, so T cell is not killed
How are B cells activated by T cells?
CD40/CD40L and cytokines
Why is T helper response for B cells important?
no AIRE expressed in bone marrow - more likely to respond to self
What does no germinal centers in lymph nodes suggest?
no t cell help for b cells
How does dose induce/maintain tolerance?
a higher or lower does outside the range of immunological response induces tolerance
How does maturity induce tolerance?
more easily generated in immature animals
How does immunogenicity induce tolerance?
weak immunogen requires less stringent regime for induction than a strong one
How does the form of a substance induce tolerance?
aggregated can be immunogenic, but disaggregated can become tolerogenic (related to antigen processing/presentation)
CTLA-4
binds to B7 much more tightly than CD28 and blocks further activation of T lymphocyte
How does portal of entry induce tolerance?
subcutaneous/intradermal usually IMMUNOGENIC - IV/orally usually induce tolerance
What type of antigen induces humoral immunity and CMI?
protein antigens - not polysaccharides and lipids for CMI
What is FOXP3?
transcription facot - turns down immune response in t reg cells
What is antigen blocking?
antibody sequestering antigen - binds antigen and prevents it from being recognized by other antigen recognizing cells
IgM immune complex does what?
binds to antigen presenting cells and aids in presentation to b and t cells - ENHANCES immune response
