Antigen non-specific activities in culture supernatants from clones of a radiation leukemia virus transformed, ovalbumin-specific helper T lymphoma were studied. After stimulation with ovalbumin-pulsed macrophages, these clones release factor(s) capable of providing carrier-specific help for anti-hapten antibody responses. It was found that in addition to IL 2-like activity, one clone constitutively released a suppressive factor that could inhibit polyclonal growth and differentiation of B cells stimulated with LPS. The factor inhibited activation of both syngeneic and allogeneic B cells directly, rather than via activation of accessory suppressor T lymphocytes. However, upon dilution of the supernatant, B cell growth and differentiation activities were detected. A role for a polyclonal B cell suppressor factor in the overall helper activity of the clone is proposed.