Neonatal mouse CD4+ mature thymocytes show responsiveness to interleukin 2 and interleukin 7: growth in vitro of negatively selected V beta 6- and V beta 11-expressing CD4+ cells from (C57BL/6 x DBA/2)F1 mice.

By three colour flow microfluorimetry, we have recently shown that neonatal mouse CD4 single positive thymocytes are a population of proliferating cells. Furthermore, analysis of CD4+ thymocytes from (C57BL/6 x DBA/2)F1 mice showed that they proliferate regardless of whether they express particular V beta-encoded TCR molecules (V beta 6 and V beta 11) that are undergoing intrathymic deletion. In this report, cell culture experiments demonstrate that unstimulated neonatal CD4+ thymocytes from such mice proliferate in vitro in response to a combination of r-IL-2 and r-IL-7. Simultaneous three colour analysis of V beta TCR, CD4 expression, and DNA content of these cultured cells shows that V beta 6+, -8+, and -11+ cells grow equally well. Experiments where cells were cultured overnight in unsupplemented medium did not reveal preferential loss of negatively selected (V beta 6+ and V beta 11+) subpopulations of CD4+ cells. Taken together, these results suggest that IL-2 and IL-7 play a role in the intrathymic proliferation of developing mature T cells.