T lymphocyte number and functions in paroxysmal nocturnal haemoglobinuria (PNH). A preliminary report

T lymphocyte counts in the peripheral blood, lymphocyte response to phytohaemagglutinin (PHA) and delayed hypersensitivity reactions were studied in ten patients with paroxysmal nocturnal haemoglobinuria (PNH). Delayed hypersensitivity was abnormal in most patients and in vitro studies revealed impaired lymphocyte transformation to PHA in 50 per cent of the cases. These tests gave evidence of a functional alteration of lymphocytes in some PNH patients. The hypothesis of a disorder originated in a pluripotent lymphohaematopoietic stem cell is suggested.