Failures of the immune system Flashcards
primary immunodeficiencies
are rare genetic diseases caused by single gene defects, mutations, etc that cause children to be born without some aspect of the immune system
B cells are made in the …
bone marrow
T cells are generated or emerge from the …
thymus
if children is born with epithelial effect in thymus (thymus fails to develop i.e. no T cells), this is called ..
Digeorge syndrome
if a child has a loss of function of the absence of T cells, then they have no B cell help so cell mediated and humoral immunity are defective
SCID - severe combined immunodeficiency
* no functional T cells
comon cause of scid:
no machinery to link VDJ segements - kids born with no T or B cells (RAG type SCID)
loss of IL-7 function (X-linked SCID)
what cytokine is needed to drive the lymphoid progenitor (made from stem cell) to differentiate into T cells
What is the disease when there is a genetic deficiency for this cytokine
IL-7
lymphoid progenitor has receptor for IL-7
X linked SCID
the absence of functional BTK enzyme in the expansion of B cells causes there to be no expansion i.e. no B cells
what is the disease?
X-linked agammaglobulinemia (XLA)
- development of B cells is impaired
- No BTK
self tolerance:
this is the process of “testing” T cells in the thymus after expansion to see which are self-reactive (central tolerance)
the self-reactive ones get a sigal to curl up and die
the rest of the T cells exit to body periphery
however, sometimes cells are missed so we need mechanism using regulatory T cells (peripheral tolerance) too to supress self-reactive cells that escape from thymus
clonal deletion
self tolerance:
in peripheral tolerance of T cells that exit thymus, … is used to dampen the effector T cells that are self-reactive
regulatory T cells
* can suppress effector B and T cells.
self tolerance process:
in the case of B cells (from bone marrow) the process of self tolerance is called …
instead of killing the self-reactive b cells, we allow them to go to another round of gene rearrangement to become edited and no longer self reactive
(T cell process kills them)
receptor editing of B cells
There are three major mechanisms of immunological tolerance:
- T cell central tolerance is mediated by clonal deletion of self-reactive cells.
- T and B cell peripheral tolerance is mediated in part by regulatory T cells that suppress self-reactive cells.
- B cell central tolerance is mediated mainly by receptor editing.
B cell and T cell receptor diversity is generated by ….
V(D)J recombination
mechansims of autoimmune diseases can be either due to:
antibodies ex: myathenia gravis, Lupus
T cells ex: type 1 diabetes, psoriasis
autoimmune disease where muscle receptors are blocked by antibodies, actylcholine unable to bind to receptors, prevents neuromuscular tramsmission
droopy eye, nerve unable to send signal
myasthenia gravis
* autoimmune caused by antibody dysfunction
autoimmune disease where glomerulus is not normal, antibodies form immune compelxes (with complement) depoist in different areas, cause inflammation that damages kidney vessels
kidney disease
patients have rash on cheeks
Lupus
autoimmune disease caused by T cell dysfunction
inflammation of pancrease
reduced insulin production
T cells attack cells of the pancreas
type 1 diabetes
autoimmune disease caused by T cell dysfunction
T cells cause inflammation in the skin
psoriasis
* the most common autoimmune
most common form of immune disease
occurs in genetically susceptible individuals in response to harmless environmental agents
invovles IgE, mast cells, eosinophils
allergy
what is the first step of an allergic reaction? exposure to allergen (usually a protein) causes a B/T cell response that results in antibody class switching to IgE * IgE then binds to mast cells Fc recpetor all over body
sensitization
in the second step after sensitization, re-exposure to allergen leads to …
- allergen binds to IgE on mast cells causes cross linking - signal in cells to release granules (histamine, prostaglandins, cytokines like TNF)
- vascular leak - inflammation
- Mast cell degranulation can cause rashes, airway obstruction, GI symptoms, and severe systemic symptoms
mast cell activation
naive T cells -> TH2 cells -> IL-4/IL-5 -> … -> relases granules like proteases
this process also contribules to allergic inflammation
eosinophil activation
the response to allergen binding to IgE on mast cells is called the …
clinically manifests as rashes, airway obstruction, naursea, GI issues, vomiting
immediate hypersensitivity reaction
