CD4 and infection: In this study, we first extended this finding by demonstrating that B cells or DC loaded with a low, 10−3 multiplicity of infection (MOI) of R5-tropic HIV-1BaL could trans infect phytohemagglutinin (PHA)/IL-2-activated CD4+ T cells, with the efficiency of trans infection being significantly greater for B cells than DC (one-way analysis of variance [ANOVA], P < 0.0001, Fig. 1A).