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nbme 11 - mili99
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02-05-2012, 06:23 PM
laser scanning microscopy-- BM derived stem cell migrate throughout the thymus.result of this processes---
1.cd40 induction 2.germinal center formation 3.membrane immune globuline expression 4.thymic involution 5.T lymphocyte antigen receptor selection
02-06-2012, 07:11 AM
sorry mili, just saw your equations. The answer is 5.
It's the process of negative selection in T cell maturation to eliminate the T cells that react with self antigens with high affinity.
02-06-2012, 07:58 AM
ANS is5.
The thymus, is the principal organ responsible for the T cell's maturation. All T cells originate from haematopoietic stem cells in the bone marrow. Haematopoietic progenitors derived from haematopoietic stem cells populate the thymus and expand by cell division to generate a large population of immature thymocytes. The earliest thymocytes express neither CD4 nor CD8, and are therefore classed as double-negative (CD4-CD8-) cells. As they progress through their development they become double-positive thymocytes (CD4+CD8+), and finally mature to single-positive (CD4+CD8- or CD4-CD8+) thymocytes that are then released from the thymus to peripheral tissues. About 98% of thymocytes die during the development processes in the thymus by failing either positive selection or negative selection, whereas the other 2% survive and leave the thymus to become mature immunocompetent T cells. Positive selection "selects for" T-cells capable of interacting with MHC. Negative selection removes thymocytes that are capable of strongly binding with "self" peptides presented by MHC. |
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