Treatment with OVA and anti-CD4 mAb causes a significant loss of OVA-specific CD4+ transgenic T cells by six days post-mAb treatment whereas this loss is significantly reduced by co-treatment with the anti-CD8 mAb. BALB/c mice were injected with 2.5 × 106 CD4+ KJ1-26+ cells isolated from BALB/c DO11.10 mice and, on the same day, either left without further treatment or, treated with either OVA alone or, OVA and anti-CD4 mAb plus isotype control or, with OVA and anti-CD4/anti-CD8 mAb cocktail. On day 6 after OVA and mAb treatment splenocytes were isolated from all mice and the total number of CD4+ KJ1-26+ was determined for each mouse by FACS. Data shown are mean ± SEM for each group and are representative of 2 experiments. * indicates statistical significance to 0.01–0.05. *** indicates statistical significance to 0.0001–0.0009. The Student t test was used to determine statistical significance. n = 3 per group.