Immune Response Flashcards
T/F: a microbe must be whole to be detected by immune cells and considered an antigen
FALSE
Antigens can be entire microbes, parts of microbes, bacterial toxins, pollen, transplanted organs, or incompatible blood cells
5 Characteristics of Antigens
- Immunogenicity
- Specific Reactivity
- Foreignness
- Size
- Shape
Immunogenicity
Antigen’s ability to stimulate specific (humoral or cellular) immune response
E.g. the ability to cause the formation of Ab and T-cells
Specific Reactivity
Capacity to be recognized by the Ab and T-cells
(E.g. ability to bind to the immune cells already produced)
Foreignness
Ability to be recognized as non-self
What size must an antigen be to be recognized?
At least 10 kd
The extent of antigenicity is determined by…
The antigen’s tertiary and quaternary structures
Antigens that are more _____ (simple/complex) are more likely to be detected
Complex
This is why plastics used in joint replacements are simple repeating subunits, to not elicit an immune response
Eptitope
Antibody-binding site on the antigen
The binding triggers the immune response
Hapten
Smaller substance that cannot trigger an immune response unless attached to body protein of Ab already formed
What determines the great diversity of antigen receptors on immune cells?
Genetic Recombination of small gene segments
Explain the process of antibody-mediated immunity binding
Antigen presented to B-cell in lymphatic tissue/organs and then B-cell differentiates into plasma cells to secrete Ab —> Ab circulates and attach to epitope of antigen
Functions of an antibody (5)
- Agglutination and precipitation
- Neutralization
- Immobilize
- Complement Activation
- Enhance Phagocytosis (via precipitation, complement, or opsonization)
Antibodies consist of _____ chains, linked by ____ bonds
Polypeptide chains linked by disulfide bonds
The c in Fc portion of an antibody stands for
Crystallizable
Describe the structure of an antibody
T or Y shaped monomer of 4 polypeptide chains (2 heavy and 2 light)
How does IgM bind to surfaces of B-cells?
Through the membrane, as an integral membrane protein
T/F: Surface IgM are structurally different than circulating IgM
TRUE
In the Fc region
What form of IgM is typically found in blood?
5-unit macromolecules (pentamers)
Which antibody is the first to be produced in response to an infection?
IgM
Which antibody can exist as a monomer or a dimer?
IgA
Most abundant Ab in blood?
IgG
Ab found most in response to parasitic infections
IgE
Which Ab is secreted the least?
IgD
IgA is most common and most active where?
Mucosal surfaces
The dimeric Ab is bound together via
J chain
How does IgA transport through cells?
It receives a secretory (“pass”) from epithelial cells that binds to its surface and allows it through
What is colostrum?
What Ab is associated with it?
First secretion of breast milk, after birth
Associated w/ IgA
What Ab is the only class able to pass placental barrier
IgG
Which Ab is the best for opsonization?
IgG
Which Ab is associated with Type 1 Hypersensitivity reactions?
IgE
What are the differences between primary and secondary response?
Primary: slow onset, low in magnitude, short lived, IgM
Secondary: rapid, high in magnitude, long-loved, IgG (or IgA, IgE)
HLA
Human Leukocyte-Antigen System — group of proteins called Major Histocompatibility Complex (MHC) presented on cell surfaces and help distinguish between self-cells and foreign cells.
Which class of MHC (I/II) is found on almost all cells?
What are the types?
MHC 1:
A, B, and C
Which class of MHC (I/II) is found on immune cells?
What are the types?
MHC II:
D (DP, DQ, DR)
