Module 2: Antigens and antibodies Flashcards Preview

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Flashcards in Module 2: Antigens and antibodies Deck (50)
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1

antigen

a variety of large molecular structures that can interact with an antibody or a t cell receptor

2

immunogens

antigens that are recognized by a persons immune system as foreign or abnormal and which therefore cause an immune response
Not all antigens are immunogens

3

tolerogens

antigens for which an individual developed tolerance in contrast to an immunogen which evokes an immune response.
Self antigens are usually tolerated

4

Allergens

antigens that elicit production of IgE antibodies instead of IgM/IgG of normal immune response

5

Antigenicity

potency of an antigen

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Hapten

chemically active substance with LOW molecular weight that is unable to induce an immune response by itself but when conjugated with a carrier molecule, it becomes immunogenic

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heterophile antibodies

endogenous antibodies present in human serum that may interfere with various immunoassays

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Heterophile antigens

an antigen common to more than one species

ex. exposure to e coli early in life initiates anti B production in blood group A and O individuals

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epitope

epitope of an antigen is the exact structural component either on or within an antigen with which an antibody reacts

AKA antigenic determinant

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Carrier region

regions on the antigen structure to which antibody is not formed

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Specificity

exact anatomic and molecular characteristics of the epitope that enables it to be recognized and classified

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9 factors affecting ability of antigen to evoke an immune response

Chemical nature of antigens (proteins/IgG are best; polysaccharides/IgM less immunogenic; lipids, nucleic acids and inorganic substances not immunogenic)

Chemical complexity

Molecular size

Structural conformation of the molecule

Ionic charge (high charge could decrease immunogenicity)

Foreignness

Route, dosage, frequency of exposure to immunogen

Genetic composition of host (age, health)

Adjuvants

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Adjuvants

agents that can be administered with antigen that enhance the immune response

not immunogenic on their own

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2 ways antibodies are produced by b lymphocytes and secreted through the exocytosis pathway

Membrane bound
Secreted form

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Membrane bound antibody production

antibody serve ad the b cell antigen receipt (site on b cell which will bind with corresponding antigen)
If they make contact with specific antigen, B cell differentiates and becomes an antibody forming plasma cell

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Secreted form antibody production

plasma cells secrete free antibody into the blood or lymph
Secreted ab promote phagocytosis, neutralize antigens and activate complement

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2 types of light chains

kappa
lambda

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5 kinds of heavy chains

differentiate the class of antibody

IgM mu chains
IgG gamma chains
IgA alpha chains
IgD delta chains
IgE epsilon chains

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domains

loops of about 110 amino acids in the heavy and light chains

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constant domains of heavy chains

have the same amino acid sequence for all antibodies in a class

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constant domains of light chains

have the same amino acid sequence for either kappa of lambda light chains

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Variable domains (VH and VL)

have amino acid sequences that are specific to the epitope of the antigen that induced antibody production

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function of variable light domain

determines antibody specificity
site of antigen binding

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function of constant light domain

determines if chain is kappa or lambda
orientates antibody during antigen binding

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function of variable heavy domain

determines antibody specificity
site of antigen binding

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function of constant heavy 1 domain

orientates antibody during antigen binding

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function of constant heavy 2 domain

involved in complement activation

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function of constant heavy 3 domain

involved in phagocyte binding

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Fab (fragment antigen binding) fragment

consists of entire light chain and half of heavy chains
NH2 (amino) end of the antibody
Site that recognizes and binds antigen (epitope)

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Fc fragment (fragment crystallizable)

consist of other half of heavy chain
COOH end
Functions: Complement activation
Macrophage attraction when coating an antigen
Placenta expresses Fc receptors; allow binding of maternal IgG molecules for transport across placenta to baby
May be labeled for in vitro detection of antigen