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NNL Awaitin The Unexpected Topics: 779 Posts: 6613	Apr 12, 2007 - 4:45 AM       #1 A superantigen is a bacterial product that A. binds to B7 and CD28 costimulatory molecules B. binds to the b chain of TCR and MHC class II molecules of APC stimulating T cell activation C. binds to the CD4 + molecule causing T cell activation D. is presented by macrophages to a larger-than-normal number of T helper CD4 + lymphocytes E. stimulates massive amounts of IgG synthesis because of its large size
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al-fateh Forum Newbie Topics: 3 Posts: 13	Apr 12, 2007 - 5:08 AM       #2 A
Feyza Forum Guru Topics: 51 Posts: 1413	Apr 12, 2007 - 6:02 AM       #3 B and the bugs doing this are staph aureus with its TSST-1 and strep pyogenes with its erythrogenic toxin...thus stimulating release of IFN gamma and IL 1...
salmonella Forum Elite Topics: 46 Posts: 289	Apr 12, 2007 - 6:20 AM       #4 B agree
keepgoing ..... Topics: 109 Posts: 1865	Apr 12, 2007 - 7:58 AM       #5 b
usmle4me Forum Elite Topics: 6 Posts: 281	Apr 12, 2007 - 11:29 AM       #6 B.Polyclonal activatorsof Th cells.TCR B chain to MHC II.
NNL Awaitin The Unexpected Topics: 779 Posts: 6613	Apr 12, 2007 - 1:33 PM       #7
NNL Awaitin The Unexpected Topics: 779 Posts: 6613	Apr 12, 2007 - 1:33 PM       #8 The correct answer is B. A superantigen, such as TSST- 1 or staphylococcal enterotoxin, cross-links the variable domain of the TCR b chain to the MHC class II molecule and specifically induces massive T cell activation. The superantigen does not bind the B7 and CD28 costimulatory molecules (choice A). Instead, the costimulatory molecules bind to each other to stimulate the reaction between the antigen-presenting cell and T cell. The superantigen does not bind the CD 4 molecules (choice C) but instead binds on the other side of the TCR receptor complex. The term superantigen has nothing to do with the antigen being presented by macrophages to T cells (choice D). The term superantigen has nothing to do with its size or its ability to stimulate antibody production (choice E). The term superantigen is used because of its unusual ability to create massive T cell activation by the unique type of binding.

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