Immunoglobulin production after marrow transplantation. III. The functional heterogeneity of FC-IgG receptor positive and negative T cell subpopulations.

Ten patients with chronic graft-versus-host disease (GVHD) after HLA-identical marrow transplantation were studied between 372 and 1649 days post-transplant for their T cell subset functions in pokeweed mitogen-stimulated immunoglobulin (Ig) synthesis. In vitro Ig synthesis was assessed using an indirect haemolytic plaque assay after 6 days of culture. T cells, TG+ cells (Fc-IgG receptor positive), TG- cells (Fc-IgG receptor negative), and B cell-enriched populations from the patients were co-cultured with normal T and/or B cells. Such cultures in patients with chronic GVHD showed deficient B cell activity (eight of 10); and deficient helper activity in T cells (six of 10), TG+ cells (five of nine), and TG- cells (three of nine). Greater than 50% suppression of Ig synthesis was detected with T cells (four of 10), TG+ cells (three of 10), and TG- cells (three of 10). This study provides evidence for variable regulatory function of Fc receptor T cell subsets in patients with chronic GVHD. The unexpected finding was that TG+ and TG- subpopulations can lack helper activity or actively suppress Ig synthesis.