Neonaltal mouse CD4+ mature thymocytes show responsiveness to interleuking 2 and interleukin 7: Growth in vitro of negatively selected V_β 6- and V_β 11-expressing CD4+ cells from (C57BL/6xDBA/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 × DBA×2)F1 mice showed that they proliferate regardless of whether they express particular vyencoded TCR molecules (V_β6 and V_β11) 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 Vs TCR, CD4 expression, and DNA content of these cultured cells shows that V_β6⁺, -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_β6⁺ and V_β11⁺) 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.