Immunology lecture 02
Terms
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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?
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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?
- 4
- How many subclasses does IgA have?
- 2
- 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