Mark all appropriate answers. Presentation of exogenous antigens (as opposed to

Question

Mark all appropriate answers.

Presentation of exogenous antigens (as opposed to that of endogenous antigens) involves fragmentation into antigenic determinants by a proteasome viral antigens only MHC class I only both MHC class I and class II transport of antigenic peptides by TAP-1 and TAP-2 all of the above none of the above Thymic education of a maturing T cell involves apoptosis of thymocyt es with nonproductive generic rearrangements for the TcR apoptosis of thymocyte whose TcR can not bind self-MHC. apoptosis of thymocytes whose TcR bind self-MHC, but bind too well. apoptosis of thymocytes whose TcR binds self- MHC plus antigen too well discontinuation of expression of either CD4 or CD8, depending upon whether the TcR binds MHC class II or lass I, respectively. all of the above none of the above Positive selection refers to apoptosis of self-reactive thymocytes, and is uncommon involves apoptosis of thymocytes with TcR binding ANY antigen in any self-MHC protein involves apoptosis of thymocytes with TcR binding only self antigen in self-MHC proteins involves apoptosis of thymocyte with TcR binding only nonself antigen in self-MHC is not involved in self-nonself discrimination or tolerance of self interferes with otherwise orderly differentiation and m; turation of thymocytes into functional T cells none of the above. Negative selection involves preprogrammed death of cells with TcR which can bind ANY antigen in self-MHC proteins, involves preprogrammed death of cells with TcR which can bind ONLY SELF antigen in self-MHC involves preprogrammed death of cells with TcR which can bind ONLY NONSELF antigen in self-MHC. is not necessary for self-nonself discrimination. interferes with an otherwise orderly education of thymocytes. refers to NONE of the above.

Explanation / Answer

5. The exogenous are processed by the fragmentation into antigenic determinants by the proteasome, they are transported to TAP1 and TAP2 and they are expressed only by MHC II molecules. The answer is A and C

6. Thymic education of T cells happens in the thymus during the T cell development. The T cells are presented with self MHC and self-antigens to undergo negative selection. In this apoptosis of thymocytes whose TcR binds self-MHC with self MHC too well. So the negative selection will kill the thymocytes that can bind to self-peptides with high affinity. The answer is all of the above.

7. Positive selection indicates that selection occurs when double positive t cell bind cortical epithelial cells expressing either class I or class II MHC plus self-peptides with high enough affinity to get survival signal. The answer is only C

8. Negative selection occurs when double positive T cells bind to bone-marrow derived APC (macrophages and dendritic cells) expressing Class I or Class II MHC plus self-peptides with a high enough affinity to receive an apoptosis signal. The answer is only B

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