SLAMF1 and lymphopenia: Similarly to the severe lymphopenia observed in children [3], [25], MV infection of suckling CD150 transgenic mice greatly reduced the number of lymphoid cells: the number of splenocytes 10–14 days after infection (dpi) was regularly lower in infected transgenic mice (4.7±2.1×107) than in infected nontransgenic littermates (9.2±3.6×107) (for 15 and 12 mice respectively, p<0.05, student t-test).