Autoimmunity Flashcards
Paul Erlich (1900s) introduced the phenomenon he called “__________” or “_________”
“horror autotoxicus” or “fear of self-poisoning”
The immune system could attack the very host it was intended to protect
“horror autotoxicus” or “fear of self-poisoning”
___________ are targeted toward self-antigens resulting to organ and tissue damage
immune response
Can be caused by T-cell–mediated immune
responses or autoantibodies that are directed
against host antigens
autoimmune diseases
The ability of the immune system to accept
self-antigens and not initiate a response against
them
self tolerance
A state of immune unresponsiveness that is directed against a specific antigen, in this case, a self-antigen
immunologic tolerance
2 levels of immune tolerance
central tolerance
peripheral tolerance
Occurs in the central or primary lymphoid organs,
the thymus, and the bone marrow; Negative and
Positive Selection during T cell maturation; Receptor editing in B cells
central tolerance
Can result from anergy (a specific state of
unresponsiveness to the antigens) caused by the
absence of a costimulatory signal from an
antigen-presenting cell (APC) or binding of inhibitory receptors such as CTLA-4 (a molecule that prevents T-cell activation)
peripheral tolerance
A molecule that prevents T-cell activation
CTLA-4
More prevalent among family members and among monozygotic (genetically identical) twins than dizygotic (non-identical) twins or siblings
genetics
Women are 2.7 times more likely to acquire an
autoimmune disease than men; about 78% of
patients with autoimmune diseases are females; the stimulatory effects of female hormones may place women at a greater risk for developing autoimmune disease
hormonal influence
female hormones affected in autoimmune disease
Estrogen
Androgen
Prolactin
“Immunologic tolerance” some self-antigens may
be cryptic, or hidden within the tissues of the host. T and B lymphocytes are shielded from these
sequestered antigens and are not educated to
become tolerant to them
TISSUE TRAUMA AND RELEASE OF CRYPTIC ANTIGENS
TISSUE TRAUMA AND RELEASE OF CRYPTIC ANTIGENS
Tissue damage could be caused by factors such as:
infections
contact with environmental toxins
physical injury from exposure to ultraviolet (UV) radiation
Bacteria, viruses, and other infectious pathogens
may be able to trigger autoimmune responses
microbial infections
many bacterial or viral agents
contain antigens that closely resemble the structure or amino acid sequence of self-antigens
molecular mimicry
the microorganism can induce a local inflammatory response that recruits leukocytes and stimulates APCs to release cytokines that nonspecifically activate T cells; some of the T cells that are activated may have specificity for self-antigens
bystander effect
proteins that are produced by various microbes that have the ability to bind to both class II MHC molecules and TCRs, regardless of their antigen specificity
superantigens
can cause polyclonal activation of B cells
Epstein-Barr virus (EBV) and cytomegalovirus (CMV)
_______ refers to modifications in gene expression that are not caused by changes in the original DNA sequence.
epigenetics
can induce epigenetic changes by increasing or decreasing methylation of cytosine bases, modifying histones, and causing abnormal regulation by microRNAs; underexpression of certain genes in the immune system may result in
homeostatic imbalances and a breakdown of
self-tolerance, leading to autoimmunity
Triggered by exposure to environmental
toxins, ingestion of harmful foods or drugs,
or the aging process
Exposure to environmental factors can lead
to changes at the protein level; post-translational modifications and may involve biochemical processes such as:
acetylation
lipidation
citrullination
glycosylation
may cause break in immunologic tolerance,
autoreactive T cells recognize and proliferate in
response to self-antigens and B cells develop into
plasma cells that secrete autoantibodies
complex interactions between genetic and environmental factors