Heterogeneity of T-CLL defined by monoclonal antibodies in nine patients

Abstract

Surface markers were examined on peripheral lymphocytes from 450 patients with chronic lymphocytic leukemia (CLL). In nine (2%), the lymphocytes had the characteristics of thymus-derived cells (T-CLL). These nine patients had a milder clinical course than that usually attributed to T-CLL, lack of massive hepato- or splenomegaly, and fewer skin lesions. Lymphocytes from these patients were studied with surface markers, including a panel of monoclonal antibodies (MoAb) and also for in vitro functional activity. Whereas cells from two patients appear to represent heterogeneous proliferations, as detected by MoAb, seven cases gave a clearly recognized phenotype. Evaluation of immunoregulatory functions showed that OKT8 +, Fc IgG receptor-positive cells (three patients) were able to suppress either lymphocyte proliferation, or immunoglobulin biosynthesis, or both. In three patients with a proliferation of OKT4 + cells, in vitro help was not demonstrable, but in two of them, high levels of serum IgA were detected. Our results clearly show that T-CLL may originate from different T-cell subpopulations. Some, if not all of the T-CLL cells, seem to represent the proliferation of well-differentiated T cells, corresponding to the normal T-cell subsets. In some cases these cells retain functional activity. The expression of a given phenotype pattern, as detected by MoAb, represents a useful tool in determining the clonal origin of proliferating cells.