Mice immunized with the gp120/anti-CD4bs mAb complex have lower gp120-specific lymphoproliferation than mice immunized with gp120 alone or other gp120/mAb combinations. Mice were immunized with gp120 alone or gp120 mixed with anti-CD4bs mAb (654), anti-C5 mAb (670), or irrelevant anti-parvovirus mAb (1418), along with Ribi adjuvant. Each animal received 3 μg of gp120 and 10 μg of mAb. Control mice were injected with Ribi adjuvant containing no antigen (PBS). The splenocytes were tested in the 3H-thymidine incorporation assay for proliferative responses to gp120 protein (A) or pooled gp120 peptides (B).