Fig. (4) CD4 is required for gp120 inhibition of SDF- 1α induced chemotaxis. (A) Purified primary human CD4 T cells were pre-treated with either gp120 (IIIB) (1µg/ml), BSA (1µg/ml) or gp120 (IIIB) (1µg/ml) incubated with sCD4 (1:3) and then chemotactic response of CD4 T cells to SDF-1α (40nM, 1 hour) cells measured. P values were determined by Student’s paired t test. (B) Cells were pre-treated with either gp120 (IIIB) (1µg/ml), BSA (1µg/ml) or gp120 (IIIB) (1µg/ml) incubated with sCD4 (1:3) for 2 min and then stimulated with SDF-1α (40nM) for 1 min, and Factin content was measured. The data is representative of three independent experiments.