Term
|
Definition
Tolerance-state of specific
unresponsiveness to an antigen. learned
response during fetal development
developing fetuses become tolerant to any antigen to
which they are exposed during fetal development.
antigen-MHC
complex is presented to a T
cell in the *absence of the
second activation signal* |
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Term
| Self-reactive T cells that survive clonal deletion are kept in check by 3 mechanisms. |
|
Definition
. Induction of anergy;
B. Active suppression by T regulatory cells; and,
C. Sequestering of self-reactive antigens in immunologically privileged sites |
|
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Term
| Active Suppression by T Regulatory Cells |
|
Definition
have antigen-specific receptors that are specific for self antigens
express CD-4, CD-25 and
CTLA-4 on their surface, and a unique
transcriptional repressor protein in their cytoplasm called *FoxP3.*
-suppress self-reactive naive T cells several ways(CTLA-4 costimulatory molecules binds B7 with 20 times more
affinity than CD-28 on naive T cells., and Bind IL2. IL-2 does not
activate T regulatory cells to proliferate because they express the FoxP3 repressor.) |
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Term
|
Definition
occurs in T cells and develops in T cells that are exposed to very low Ag concentrations (10-50 ng/ml).
A. It is induced quickly (3-4 days).
B. Once induced it lasts for months |
|
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Term
|
Definition
occurs in B cells that are
exposed to very high Ag concentrations.
A. It takes about 1 week to induce and is
relatively short lived (a few weeks) unless there is continuous exposure to high concentrations of the Ag. |
|
|
Term
| T cell tolerance to self antigens |
|
Definition
the major mechanism for preventing the development of autoimmunity by self-
reactive lymphocytes that escape clonal deletion. |
|
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Term
| Peptidyl arginine deaminase |
|
Definition
an example of an inducible
enzyme that can modify a self-peptide, producing an
altered peptide with a new epitope that can activate T
cells and trigger autoimmunity.
arginine residues in peptides into citrulline residues
responsible for about 50% of rheumatoid arthritis cases |
|
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Term
|
Definition
Celiac disease cause
deaminates glutamine residues in peptides, forming glutamate residues.
altered
gluten peptides that active naive CD-4 T cells, produce inflammatory
cytokines that cause gut
inflammation when the
host eats gluten |
|
|
Term
| One of the best known examples of antigenic memicry |
|
Definition
rheumatic fever Group A Streptococcus produces an Ag
that has a epitope in common with an
Ag in human heart tissue |
|
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Term
|
Definition
T cells infiltrate the pancreas and destroy the Beta cells in the islets
of Langerhans. |
|
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Term
|
Definition
A disease similar to lupus erythematosus develops
spontaneously in New Zealand Black mice. |
|
|
Term
| The thymus in humans also degenerates with increasing age, |
|
Definition
This may explain why autoimmunity increases in frequency in humans
with age as shown for rheumatoid arthritis |
|
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Term
|
Definition
substances that non-specifically
activate B lymphocytes to differentiate into plasma cells.
they stimulate
a *polyclonal* antibody response to many different antigens. |
|
|
Term
|
Definition
Rheumatoid factors can be IgG or IgM
antibodies, and are present in high levels in the serum of rheumatoid arthritis patients. |
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