RESUMEN
Phenotypes of T cells regulating human tonsillar IgE biosynthesis in vitro were studied by use of Leu 2a and Leu 3a monoclonal antibodies that recognize T cell subsets. B cells cultured with Leu 3a+-enriched populations (B cells plus T3a) produced significantly more IgE and IgG in the presence of pokeweed mitogen than B cells with the Leu 2a+-enriched populations (B cells plus T2a) (p less than 0.001 for IgE and p less than 0.001 for IgG). No significant differences were observed in IgE and IgG synthesis between the cultures of B cells alone and B cells plus T2a. T2a, but not T3a cells, significantly suppressed IgE synthesis (p less than 0.05 for geometric means and p less than 0.001 for percent suppression) when the cells were added to cultures of B cells plus T3a. Suppression of IgG synthesis was not observed under conditions that suppressed IgE synthesis, suggesting qualitative and quantitative differences in regulation of production of these isotypes. When T2a cells were irradiated, the suppressor activity disappeared. When graded numbers of T3a cells were added to B cells, it was noted that IgE synthesis first increased and then decreased as the numbers of T3a were increased. When the T3a cells were irradiated, IgE biosynthesis was suppressed at lower T/B ratios (less than 1 in four of five experiments) and was enhanced at higher T/B ratios (greater than 1 in all five experiments). Similar results were observed in experiments with OKT4 and OKT8 monoclonal antibodies. It is concluded that phenotypes of helper T cells for IgE synthesis are Leu 3a+ or OKT4+ and that IgE suppressors are predominantly Leu 2a+ or OKT8+ and are radiosensitive, as reported for regulation of other isotypes. However, it is suggested that Leu 3a+ and OKT4+ cells consist of radioresistant and radiosensitive helper cells and, presumably, a minor population of suppressor cells.