TNFRSF4 and B-cell chronic lymphocytic leukemia: HIV(FIV) pseudotypes bearing Envs from GL8 or the five variants were used to infect either MYA-1 cells (low CXCR4) or CLL-CD134 (high CXCR4) in the presence of increasing concentrations of the CXCR4 antagonist AMD3100 and the 50% inhibitory concentration (IC50) estimated (Table 1).