| Abstract: | T cells from anti-mu-treated mice, normal goat serum ( NGS )-treated mice or untreated control mice were compared with respect to their surface antigenic phenotypes, T cell mitogenic responses, helper function and precursor frequency of helper T cells. Anti-mu treatment arrested the development of B cells at an immature stage, as determined by flow microfluorometry; it resulted in no serum IgM, but detectable levels of IgG by solid-phase radioimmunoassay. Proliferative responses to phytohemagglutinin and concanavalin A were significantly decreased in T cells obtained from mu-suppressed C57BL/6 mice, but not from control mice. When T cells from anti-mu-treated mice were tested in vitro for their helper activity to collaborate with B cells from nu/nu C57BL/6 mice to give plaque-forming cells to sheep red blood cells, they provided far less help than did T cells from control mice. The frequency of T helper cells, as measured by limiting dilution analysis, was much lower in the anti-mu- than in the NGS -treated mice. Cell mixing experiments provided evidence for active suppression of T helper function among splenocytes taken from mu-suppressed mice. |
