Unusual phenotype and function of an expanded subpopulation of T cells in patients with haemopoietic disorders.

We have studied two patients, one with red cell aplasia and the other with neutropenia. Both showed lymphocytosis. In both cases, 90-100% of E rosetting cells were T cells as defined by the monoclonal antibodies UCHT1 and OKT3. The majority of these cells also carried the OKT8 suppressor/cytotoxic marker and were HLA-DR- and Fc gamma R-positive. In spite of the similarity of this phenotype to that reported for suppressor cells, these cells failed to suppress pokeweed mitogen-induced polyclonal Ig synthesis. Cells from both patients also failed to respond significantly to Con A and PHA. They were, however, unable to suppress the Con A responses of normal donors although cells from one patient were able to suppress completely a normal PHA response. These results demonstrate the existence of a genuine subset of T cells with Fc gamma receptors but suggest that not all such cells have typical suppressor function.