Hypersensitivity and Immune Tolerance Flashcards
What is immunological tolerance?
specific unresponsiveness to self Ags
What is an example of a complex antigen?
bacteria -> has many epitopes
What are adjuvants?
added to Ag to stimulate response to Ag
How do adjuvants work?
- enhance cytokine production
- extend presence of Ag to activate macrophages and lymphocytes
What is central tolerance?
- occurs in thymus or bone marrow
- wants cells to recognize self; if recognition is too strong -> apoptosis
- generation of regulatory T cells -> CD4/ CD25/ Foxp3
What is peripheral tolerance?
- occurs in secondary lymphoid organs
- T cells recognize Ags but do not respond
What are the mechanisms that prevent self reaction in peripheral tolerance?
- anergy of slef-reacting cells
- T cell recognizes Ag without strong co-stimulation
- death of self-reacting cells
- suppression by regulatory T cells
What are the types of CD4 cells?
- Th1
- Th2
- Th17
- T regs -> CD4, CD25, Foxp3
What is IPEX syndrome?
- mutation in Foxp3
- lack of central tolerance
What is polyendocrine syndrome?
- mutated AIRE gene
- self Ags are not expressed in thymus
- lack of negative selection -> can respond to self
What are the responses in peripheral T cell tolerance?
- normal response -> effector and memory T cells
- anergy -> functional unresponsiveness
- suppression -> block in activation
- deletion -> apoptosis
What are the 2 types of T cells antigens in B cell tolerance?
- dependendent -> tolerance can be generated via T cells
- independent -> tolerance at the level of B cell
What are the characteristics of organ-specific autoimmunity?
- occurs when one organ is targeted
- treated with organ-specfific corrections
- ex: diabetes type 1 -> treated with insulin
What are the characteristics of systemic autoimmunity?
- widespread inflammation
- treated by general down-regulation of IS
- ex: rheumatoid arthritis -> treated with steroids
What is associated with ankylosing spondylitis?
HLA-B27
What are the factors involved with infections & autoimmunity?
- cross-section -> “little women” (rheumatic fever)
- bystander effect
- removal of sequestration
- adjuvant effect
What is type 1 hypersensitivity?
- mediated by IgE
- immediate -> seconds to minutes
- wheal and flar reaction
- Th2 response
- ex: allergic reactions
What is type 2 hypersensitivity?
- mediated by IgG & IgM
- auto Abs bind to self Ags and trigger immune response
- activates compliemtn system
- ex: rehumatic fever, graves disease, hashimoto disease
What is type 3 hypersensitivity?
- mediated by immune complexes
- complexes build up in blood vessels and kidney -> serum sickness
- ex: lupus & rheumatoid arthritis
What is type 4 hypersensitivity?
- mediated by T cells
- delayed reaction -> 24-48 hours after exposure
- contact sensitivity
- cytokine release leads to tissue injury
- ex: reaction to tuberculosis skin test
