A satisfactory quantitative test of lymphocyte response to phytohaemagglutinin for the definition of normal control values and recognition of immunological defects.

Despite widespread doubts about the quantitative validity or clinical usefulness of lymphocyte response to phytohaemagglutinin (PHA), a satisfactory quantitative test of such responsiveness suitable for the clinical recognition of immunological defects has been developed here. This was achieved by exploring and controlling technical and other variables in the culture of lymphocytes and the quantitation of their response to phytohaemagglutinin. The aspects evaluated included intraperson as well as person-to-person variations, non-lymphocytic cell content, lymphocyte number, PHA batch, atmospheric conditions, culture duration, and quantitation of response. As a result of the information gained from these studies, together with the normal dose-response curve previously established (Fitzgerald, 1971), a satisfactory quantitative and reproducible method suitable for routine clinical use has been realized. This has been applied to the investigation of patients with suspected immunological deficiency disorders, and significant deviations from the normal have been shown. In addition, a PHA dose-response ratio derived from the responses of normal individuals and patients gives a practical quantitative expression of such defects.