Thymocyte emigration is mediated by active movement away from stroma-derived factors.

T cells leave the thymus at a specific time during differentiation and do not return despite elaboration of known T cell chemoattractants by thymic stroma. We observed differentiation stage-restricted egress of thymocytes from an artificial thymus in which vascular structures or hemodynamics could not have been playing a role. Hypothesizing that active movement of cells away from a thymic product may be responsible, we demonstrated selective reduction in emigration from primary thymus by inhibitors of active movement down a concentration gradient (chemofugetaxis).

Impaired CTL recognition of cells latently infected with Kaposi's sarcoma-associated herpes virus.

Kaposi's sarcoma-associated herpes virus (KSHV) is a recently identified human gamma2-herpesvirus associated with Kaposi's sarcoma, primary effusion lymphoma, and Castleman's disease. We reasoned that CTL responses may provide host defense against this virus, and consequently, KSHV may have evolved strategies to evade the CTL-mediated immune surveillance. In this study six B cell lines latently infected with KSHV were found to express reduced levels of HLA class I surface molecules compared with B cell lines transformed by the related gamma-herpesvirus EBV.