Glossary of Immunology lecture 02

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Define antigen
Any substance that may be specifically bound by an antibody molecule or a T cell receptor
Define immunogen
Antigen that stimulates an immune response
3 Characteristics of immunogens
1. Big (>10,000d)
2. Complex
3. Foreign
Define haptens
Antigenic determinants that bind to effector cells, but do not activate them
Define Pathogen Associated Molecular Patterns (PAMPS)
Conserved molecules produced only by microbes and not by host organisms
Define adjuvants
Substances used to enhance the immune response to any immunogen. Work by delayed release of antigen
Antigens (immunogens) express:
Antigenic determinants (epitopes) which are specific and often cross-reactive
What are the compositions of some common adjuvants?
Oil in water, with mycobacteria, aluminum hydroxide gel, matrix of lipid micelles
Define antibodies
A class of heterogeneous serum glycoproteins that are 82-96% protein, 4-18% carbohydrate
Which antibodies are in the gamma fraction? The beta fraction?
Gamma: IgG
Beta: IgM and IgA
Model of IgG:
L chains are covalently attached to H chains, and H chains are covalenty attached by S-S bonds
The enzyme papain breaks antibodies into:
2 Fab fragments and 1 Fc fragment
Define multiple myeloma
A disease in which one particular immunoglobulin-producing cell (B cell) divides over and over so that the patient has an enormous number of identical B cells>>miligram quantities of immunoglobulins
What are the five classes of immunoglobulins
IgM, IgG, IgA, IgD, IgE
In man, how many subclasses does IgG have?
How many subclasses does IgA have?
Define allotypes
Inherited differences on Ig molecules, not associated with the antibody-combining site
Define idiotypes
Unique structures on a single antibody molecule which represent a unique amino acid sequence in or close to the antibody combining site
What are the characteristics of the hinge region
High in proline, contains most of the cysteines involved in disulfide bonds; important in flexibility of the molecule
How many domains does the IgG monomer contain?
12, each ~110aa long and contains an intrachain disulfide bond. These domains are the fundamental units of the immunoglobulin molecule
Characteristics of IgG
Systemic immunity (Peripheral immune system). Only class of antibody that can cross placenta; therefore, important in passive immunity of the neonate
Characteristics of IgA
Mucosal Immunity (Mucosal immune system). Body secretions. IgA1 in serum, IgA2 in secrections
Characteristics of IgM
Macroglobulin; 12% carbohydrate; occurs as pentamer, no hinge region; monomer on the cell surface of B cells (antigen-specific receptor)
Characteristics of IgD
Acts as an antigen-specific receptor on B cells
Characteristics of IgE
Responsible for immediate hypersensitivity and anaphylaxis; binds to receptor on Mast cells

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