Importantly, the infections of CD62L-CEM #2 and #25 by a replication-competent X4-tropic HIVLAI were 3-to-4-fold higher than that of the parental CEM cells as measured by intracellular viral capsid p24 staining (Fig. 2a), suggesting that L-selectin facilitated HIV-1 infection. Here, SELL is linked to infection.