[Cloning deletion of mouse medullary CD4SP thymocyte subgroups induced by superantigen staphylococcal enterotoxin B].

Objective: To investigate the clonal deletion of medullary CD4SP thymocyte subgroups induced by superantigen SEB, and to understand the stage specificity of thymic negative selection based on the developmental pathway of medullary CD4SP thymocytes we established previously.

Methods: SEB was intravenously injected into C57BL/6 mice, and then the expression of surface molecules and apoptosis of thymocytes were detected by FACS. The reduction of each subgroup of medullary CD4SP thymocytes was analyzed by FACS assay and cell counting.

Results: The percentage of apoptotic CD4SP thymocytes significantly increased after the intravenous injection of SEB. The cell number of CD4SP decreased about 43.8%. Among TCR Vbeta8(+)CD4SP thymocytes, the percentage of 6C10(+)CD69(+)Qa-2(-)thymocytes(SP1) was reduced by two thirds and the percentage of Qa-2(+) thymocytes(SP4) was comparatively increased, while the cell numbers of SP1 to SP3 decreased over 80% and that of SP4 decreased about 50%.

Conclusion: Thymic negative selection occurs during the stage of SP and goes through the whole developmental progress from SP1 to SP4.The thymocytes in the stage of SP1 to SP3 are more sensitive to apoptosis than those in the stage of SP4.