Preferential proliferation and differentiation of double-positive thymocytes into CD8(+) single-positive thymocytes in a novel cell culture medium

The identification of factors that regulate the proliferation and different iation of double-positive (DP) into CD4(+) and CD8(+) single-positive (SP) thymocytes has proven difficult due to the inability of DP thymocytes to pr oliferate, expand, and differentiate into SP thymocytes in available cell c ulture media. Here we report on the ability of DP thymocytes to differentia te in a novel conditioned medium, termed XLCM, derived from the supernatant of mitogen activated human cord blood mononuclear cells. During a 5-day cu lture in XLCM in the absence of thymic stromal cells, DP thymocytes from no rmal mice and MHC double knockout mice (lack SP thymocytes) proliferate, ex pand, and differentiate into several (alpha beta TCR+, NK1.1(+)alpha beta T CR+, and gamma delta TCR+) subsets of CD4(+) and predominantly CD8(+) SP th ymocytes. These studies suggest that the use of XLCM may aid in the charact erization of factors that regulate the differentiation of DP thymocytes int o CD8(+) SP thymocytes. (C) 2000 Academic Press.