Proliferative response of a murine CD4 T cell clone to gp120 is suppressed when gp120 is bound by anti-CD4bs mAbs. A) Mouse T cell clone T1 was tested for proliferation to different concentrations of gp120, alone or in the presence of anti-CD4bs mAb 654 or anti-C5 mAb 450 (10 μg/ml each). B) Proliferation of clone T1 was tested in response to different gp120/mAb complexes. For comparison, the response to gp120 alone is normalized to 100%. Gp120 was tested at 3 μg/ml and combined with 10 μg/ml of each mAb. Irradiated splenocytes were used as antigen-presenting cells. Average values and standard deviation from two repeated experiments are shown.