Phenotypical and functional studies on a subtype of suppressor cells (CD8+/CD11+) in patients after bone marrow transplantation.

Dual labeling with the monoclonal antibodies anti-Leu 2 (fluorescein-conjugated) and anti-Leu 15 (phycoerythrin-conjugated) was used to phenotype and sort the lymphocytes from 12 short-term (100 days postgrafting) recipients, 8 long-term (6 months postgrafting) stable, and 11 long-term patients with chronic graft-versus-host disease (GVHD). The proportion of Leu 2+ 15+ cells was increased in 11 of 12 short-term patients (mean + SEM: 31% +/- 3.6)-and in 6 of 11 patients with chronic GVHD (18% +/- 2.4) compared with normal controls (n = 8; 7.5% +/- 1.9). However, there was no correlation between proportions of Leu 2+ 15+ or Leu 2+ 15- cells and the presence of acute GVHD. Long-term patients with chronic GVHD tended to have a higher proportion of Leu 2+ 15- cells. To functionally characterize these two T cell subsets, Leu 2+ 15- and Leu 2+ 15+ subsets were sorted from purified T cells obtained from two recipients and one normal subject. Both Leu 2+ 15+ and Leu 2+ 15- cells from a short-term patient suppressed pokeweed mitogen--stimulated immunoglobulin production of normal B cells. Leu 2+ 15- cells from a long-term survivor with chronic GVHD and the normal control provided help, whereas the Leu 2+ 15+ cells also strongly suppressed immunoglobulin synthesis. The suppressor activity of the Leu 2+ 15+ subset in all three individuals was radiosensitive (12 Gy). These results illustrate the need for careful correlative phenotyping and functional studies. Furthermore, these studies clearly demonstrate that different functions may exist within a particular T cell phenotype after bone marrow transplantation.