T suppressor cell growth factor and anti-CD3 antibodies stimulate reciprocal subsets of T lymphocytes.

Because of the central role of IL-2 in clonal expansion of T cells, we have postulated that lymphocyte subpopulations with opposing regulatory functions might be independently regulated by differential requirements for expression of cell-surface IL-2-R. Purified CD4+ and CD8+ cells proliferated in an IL-2-dependent manner to crosslinked anti-T cell receptor antibodies (anti-CD3-Seph). Similarly, both CD4+ and CD8+ cells became IL-2 responsive after incubation in T suppressor cell growth factor (TsGF), a newly described approximately 8,000 Mr product of activated CD4+ cells. In support of our hypothesis, however, we observed that subpopulations of CD4+ and CD8+ cells, possessing distinct cell-surface antigens, showed differential responses to these stimuli. Those cells of suppressor-inducer or suppressor-effector phenotype failed to proliferate when cultured in anti-CD3-Seph plus IL-2, but did proliferate in an IL-2-dependent manner to TsGF. Furthermore, the suppressor-effector population was unresponsive to TsGF plus IL-2 when cocultured in anti-CD3-Seph, suggesting that functionally induced Ts may be refractory to growth stimuli. Conversely, cells with helper-inducer or cytolytic phenotype proliferated when incubated in anti-CD3-Seph and IL-2, while remaining essentially unresponsive to TsGF and IL-2. The results could not be explained by differences in the level of CD3 expression by the T cell subsets. Thus, cells within the helper and suppressor lineages appear to have distinct and reciprocal patterns for the induction of IL-2 responsiveness.

Primary culture of bovine mammary acini on a collagen matrix.

Lactating bovine mammary epithelial acini were isolated and primary culture on rat tail attached collagen gels are described. Acini rapidly attach to the gels and morphologically change little over days of culture under the culture conditions described herein. Cells release lactose, alpha-lactalbumin and alpha-s1 casein over a 6-day period. A new HPLC method for measuring lactose in mammary cell culture media is described. Comparisons of acini cultures with individual cell cultures show acini to be 1.5-5 times more productive than cells in secreting lactose and casein, respectively.