[Dysfunction and deficiency of decay-accelerating factor (DAF) demonstrated in the lymphocytes from a patient with...

A defective cell-mediated immunity was seen in a 62-year-old female with paroxysmal nocturnal hemoglobinuria (PNH). We studied the functional defect of the patient's lymphocytes and its relation to the deficiency of decay-accelerating factor (DAF) on the lymphocytes. T cells (CD 5+) and B cells (CD 20+) were obtained by cell-sorting using fluorescence-activated cell sorter (FACS-IV). These two types of cells from the patient were demonstrated to be deficient in DAF by the fluorometric measurement of DAF content using monoclonal anti-DAF antibodies. These cells were shown to be more susceptible to complement-mediated lysis than normal human lymphocytes by a complement-mediated lysis study. It was carried out by treatment of the lymphocytes with either anti-CD 5 or anti-CD 20 antibody plus rabbit complement. The lymphocytes became more susceptible to complement-mediated lysis by an additional treatment with an anti-DAF antibody both in PNH and in normal controls. From these results, we suggest that DAF plays an inhibitory role against complement activation on human lymphocytes. The mononuclear cells of the patient responded poorly to phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM). Skin tests both for PPD and for DNCB showed negative. From these findings, we suggest T cell function in the patient is impaired. Causative relations of the deficiency of DAF to the poor responses of the lymphocytes to lectins and to negative skin tests were discussed.