Immuno 4 Flashcards
all antibodies are of a class of protein called
immunoglobulin
structure of an immunoglobulin
4 polypeptide chains bound together by disulfide bonds
2 light chains, 2 heavy chains
what are the 2 regions of the immunoglobulin
variable and constant region
variable region of an immunoglobulin
(also called FAB- fragment antigen binding)
-the end of the immunoglobulin and the one that forms the structure that will bind to a specific antigen (fingers), variations
constant region of an immunoglobulin
- backbone that doesn’t have as many variable combinations (only varies from one class to another)
- (also called fragment Fc region)
5 immunoglobulins and percentages
- IgG - 80%
- IgA - 15%
- IgM - 5%
- IgD - 0.2%
- IgE - 0.002%
where is IgG usually found
epithelial tissue such as skin and conjunctiva of the eye
IgG is primarily responsible for
fixation of complement and opsonization
IgG is the principle source of ____ immunity against organisms in _____ space
humoral immunity against organisms in extravascular space
IgA is associated with ___ tissue
epithelial
what is IgA in the blood stream versus in the tissue
blood: monomer
tissue: dimeric
what is secretory IgA
is after dimer and secretory component are added
-it bathes epithelial tissue
how does secretory IgA work?
it inhibits virus particles from sticking on from epithelial surface- “it slides off like teflon paint”
in secretory IgA, what forms the monomers and what connects them to make a dimer
monomers are produced by lymphocytes
-dimer formed from connections from J chain
a unique feature of IgM is its
high molecular weight
5 monomers
IgM is especially efficient at
fixing complement (at attaching complement once it is activated to the invading organism)
what immunoglobulin is “first at the scene” at the site of infection
IgM
role of IgM is protecting _____ space
intravascular space (blood vascular system inside the vessels)
IgD
nearly all IgD appears on the surface of lymphocytes (like IgM does too)- so could be related or coordinated with IgM
IgE is also called the
“skin sensitizing antibody”
IgE normally has a physiological role to
protect mucosal surfaces
IgE triggers release of certain agents that start inflammation response such as
- vasodilation of blood vessels
- chemotactic factors which attract macrophages
what is an allergy (hypersensitivity)?
an exaggerated immune response
type I hypersensitivity is also known as
immediate Rx, anaphylaxis
what occurs during initial exposure during type I hypersensitivity ?
B cells -> plasma cells, plasma cells produce type of IgE called reagin which binds to mast cells
what occurs during second exposure during type I hypersensitivity ?
allergen binds to IgE, destabilizing the cell membrane which bursts (if the allergen bridges two IgE molecules)
-explosive degranulization releases components from mediators
explosive degranulation causes the mediators to release :
- histamine
- heparin
- prostaglandins
- proteolytic enzymes
the mix of mediators in type I hypersensitivity causes
- smooth muscle contraction
- vasodilation (redness)
- increased vascular permeability (tissue starts to lose fluid)
- mucous secretion (causing hay fever symptoms)
what occurs with the mast cell in immediate hypersensitivity?
all those packets of mediators inside the mast cells blow up and released all at once
what occurs in systemic anaphylaxis
release of a bunch of mast cells throughout the body:
-smooth muscle contraction and bronchioles constrict
-arterioles dilate, drastically reducing blood pressure
-permeability of the vessels increases and they start losing fluid
(shock)
what occurs during localized anaphylaxis
localized release of mediators- often in mucous membrane, resulting in hay fever
-if in lower respiratory tract, bronchial asthma (deeper and airborne)
type IV hypersensitivity is also called
cell-mediated, delayed
what occurs during onset on type IV hypersensitivity
subset of T lymphocytes called delayed type hypersensitivity cells (TH1) recognize antigen, react, and release cytokines which can cause tissue damage
process during type IV hypersensitivity
- T lymphocytes recruited via cytokines
- cytokines increase capillary permeability: macrophages have exaggerated response (tissue damage)
- special T cells amplify the whole thing
why is it called delayed hypersensitivity
the whole process for T cells to proliferate, send out cytokines, and recruit macrophages can take a day or two
type IV hypersensitivity is involved in what pathologies
- autoimmune diseases
- transplant rejection
- killing cancer cells
- contact dermatitis
what is contact dermatitis
occurs with certain products (cosmetics, TPAs, metals)
-it is an immune reaction to something that isn’t biologic
how can contact dermatitis illicit an immune response
small molecules called haptens when attached to a carrier (protein in the skin)- this combination is antigenic
