HIV-1 infection of MK-committed HPCs (results from a representative experiment). Cells were infected at day 0 with NL4-3 (m.o.i. 0.1 and 1, top and bottom panels, respectively) or m.o.i. 0.1 of BaL-1 strain (top panel) and p24 release was assayed in culture supernatants at different times. MK and UT-7 cells treated with heat-inactivated and infectious NL4-3 respectively, were used as negative controls. (•) MK and NL4-3; (○) UT-7 and NL4-3; (▴) MK-inactivated NL4-3; (▵) MK BaL-1.