CD4 and infection: In this assay, b12 appeared to be slightly more potent against primary CD4+ T cell mediated infection (Figure 3A and C) compared to Jurkat cells (IC50 = 7.13 μg/ml in primary cells and 16.14 μg/ml in Jurkat cells) but like other CD4-binding site antibodies it also showed reduced potency compared to J3.