ANTIGENS & IMMUNOGENICITY Flashcards
(18 cards)
*Immunogen is
*Immunogen: a stimulus that produces a humoral or cell-mediated immune
response
*Antigen:
any substance that binds specifically to an antibody or a T-cell
receptor
*Epitope:
the portion of an antigen that is recognized and bound by an Ab or
TCR/MHC complex
*Hapten:
a low molecular weight molecule that can be made immunogenic by
conjugation to a suitable carrier
The two attributes of antigenicity are:
Induction of an immune response (immunogenicity).
Specific reaction with antibody or sensitized cells (immunological reactivity).
Examples of haptens are
antibiotics, analgesics Penicillin, and other low molecular weight compounds.
What are cytokines?
Low molecular weight hormone-like proteins or
glycoproteins
Actions of cytokines
Pleiotropy
Redundancy
Synergy
Antagonism
pleiotropy
multiple biological actions
redundancy
the phenomenon in which, and the ability of, multiple
cytokines to exert similar actions
synergy
two or more cytokines acting together
antagonism
cytokines causing opposing activities
The Humoral Immune Response
The Humoral Immune Response (HIR) is the aspect of immunity that is mediated by secreted antibodies produced in the cells of the B lymphocyte lineage called plasma cells
igG
Dominant Ig in immune response.
* Major antimicrobial activity in plasma and extravascular fluids (in milk
also).
* IgG1, IgG3 & IgG4 cross placenta.
* IgG3 most effective complement activator > IgG1»_space; IgG2; IgG4 does
not activate complement.
* IgG1 & IgG3 bind with high affinity to Fc receptors (FcγR) on phagocytic
cells mediating opsonization
igA
Monomer in serum and Dimer in secretions.
It is secreted in quantities more than any other Abs.
IgA-secreting plasma cells are concentrated along
mucus membrane surfaces (MALT).
Doesn’t activate classical complement pathway.
It does not crosses the placenta.
Secretory IgA is important in defense against
bacteria and viruses
igM
Monomeric IgM is expressed as
membrane-bound antibody on B
cells (B-cell receptor).
IgM is secreted by plasma cells as
a pentamer in which 5 monomer
molecules joined by disulphide bonds
and a J (joining) chain
First to appear in neonate and in the normal immune response.
It does not cross placenta and does not diffuse well in tissue fluids.
It does not have hinge region.
igE
Slightly larger, more rigid than IgG.
No hinge.
Classical antibody of anaphylaxis (Type I
allergies) and certain parasitic infections
igD
Largely confined to membrane of mature B-cell
together with membrane IgM.
Not expressed on immature B-cells
