FIG. 2.

Blocking of T-lymphocyte effectors with monoclonal antibodies to CD4 and CD8 suggested that both CD4⁺ and CD8⁺ T lymphocytes were parasite-specific, MHC-restricted CTL. Killing was present without antibody blocking, when CD4⁺-T-lymphocyte effectors were blocked and when CD8⁺-T-lymphocyte effectors were blocked. When subsets were concurrently blocked, killing was reduced by 75%. Results are from a single experiment with cow 562 effectors, with findings representative of two experiments per cow. The effectors were 95% CD4⁺, 1% CD8⁺, and <1% γδ T lymphocytes by flow cytometry. Error bars indicate the SEM.