Glossary of Microbiology Chapters 16,17,18, and 20.

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This accounts for about 10-15% of the antibodies in serum, but is the most common in bodily secrections like saliva, tears, mucus membranes and breast milk. IgA is the most abundant immunogglobin in the body. Used mostly for prevention of attachtment of pathogens, particularly viruses and certain bacteria, to mucosal surfaces.
Make up only about .2% of total antibodies in the serum. These are found in blood and in lymoh and on the surface of B cells. They soley act as antigen receptors on B cells.
Only consist of .002% of serum. They participate in allergic reactions. When pollen interacts with a cell that is binded to IgE than the cell will release histamine.
Antigen antibody complex
This is when an antibody binds to an antigen through the antigen-binding site. The antibody attachtment to the antigen does nothing to harm it, it sijmply tags it as forgien so that the complement and phagocytes acan get to it.
Mechanisms of the antibody
Agglutination: When the antibody binds to more than one antigen at once, clumping them.
Nuetralization: When antibodies inactivate viruses by blocking their attachtment sites and inactivates bacterial toxins by blocking their binding sites.
Opsinozation: When the bacterial cell is covered in antibodies which aid in phagocytosis.
Antibody dependent cell mediated cytotoxicity: like opsonization.
This is what communicates between the cytokine cells. Interlukin 2 is produced by CD4 cells, and aids in T cell proliferation.
T cells
These are the key cellular compnent in immunity and they develope from stem cells in the red bone marrow, and then mature in the thymus. There are four kinds:
Helper T cells
Suppressor T cell
Hypersensitivity T Cells
Cytotoxic T cell
Helper T cells
CD4 cells, which contain memory cells. These cells use cytokines to influence the activity of other immune system cells. Helper T cell activation:
1) antigen presenting cell 1st encounters and processes an antigen
2) Binding of Th cell to an antigen MHC complex on the APC stimulates APC to secrete IL-1.
3) IL-1 activates the Th cell to produce IK-2. This activates mature Th cells to be made.
4) repeat step 3 w/ more Th cells.
Cytotoxic (killer) T cells
Destroy target cells on contact. Because some bacteria and viruses roduce inside host cells phagocytosis cannot get to them, the Tk can.
1) the Tk cell binds with the MHC-antigen complex on the cells surface and
2) the Tk releases a protein called perforin. This forms a pore in the membrane of the target cell, causing
3) lysis.
Delayed Hypersensitivity T Cells
These are associated with certain allergic reactions, such as to poison ivy and the rejection of transplanted tissue.
Suppressor T cells
The are thought to be T cell that regulate the immune response by turning it off when an antigen is no longer present.
T-dependent antigens
These are antibodies that are made with the help of t cells. They are mainly protein. Process:
1) The antigen is ingested and processed by an APC. Fragments are presented on the surface of the APC in the close proximity to MHC molecules.
2) A Th cell specific for that antigen reacts with the MHC-antigen complex(recognized the complex as a whole)
3) The Th cell reacting with the MHC -antigen complex then produces IK-2 that influences a B cell to
4) differentiate into a plasma cell that begins to produce humoral antibodies.

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