Characteristics of human mononuclear cell fractions separated on the basis of theophylline sensitivity of E rosette forming ability.

T lymphocytes may be separated into theophylline-sensitive (Tsens) and theophylline-resistant (Tres) fractions based on their loss or retention of ERFC-forming ability after incubation with 3 mM theophylline. It has been claimed that Tsens cells have a predominant suppressor function, whilst Tres cells have mainly helper activity. We have studied the sensitive and resistant fractions to ascertain their degree of homogeneity with regard to putative markers for helper and suppressor function. Incubation with theophylline caused no significant change in the expression of OKT3, OKT4, OKT8, and OKM1 antigens. Compared to Tsens, Tres contained significantly more cells expressing OKT4 or Leu 3A antigens and cells bearing Fc mu receptors or containing Gall bodies. The Tsens fraction was enriched for cells with Fc gamma receptors but not for cells expressing OKT8 or LEU 2A. The results suggest that the Tres fraction is enriched for cells with putative helper markers and that the Tsens fraction is enriched for cells with some suppressor markers but also contains a large number of cells of monocytic lineage. However, the two fractions are not homogeneous with respect to Fc receptor status, presence of Gall bodies or antigens defined by OKT or Leu antisera, hence the use of theophylline sensitivity as a means of estimating the sizes of the helper and suppressor populations does not seem advisable.