An Analysis of the Lymphocytotoxic Activity Found in Sera from Patients with Hypogammaglobulinaemia

Sera from 59 patients with hypogammaglobulinaemia (hypogamma) were assessed for lymphocytotoxic activity. The activity was compared wilh that found in sera from patients with systemic lupus erythematosus (SLE) in titre, class of antibody, target cell, and complement requirements. Sera from patients with hypogamma showed cytotoxic activity when compared with sera from normal donors; however, the activity was far less than that in sera from SLE patients. The cytotoxic titre of both hypogamma and SLR sera was greater against T cells than non‐T cells. Sera showing activity could be used to sensitize lymphocytes and render them susceptible to subsequent lysis, but IgM was not detectable on the surface of the sensitized cells. Following sucrose density gradient fractionalion of the sera the lymphocytotoxic activity was recovered in those fractions that contained IgM. Lymphocy‐lotoxic activity was dependent on classical complement pathway activity. In all the experiments the hypogamma sera showed the same pattern of activity as the SLE sera, but the activity was always far weaker than that found in SLE sera. The evidence does not suggest that lymphocytotoxicity is likefy to be important in the pathogenesis of hypogamma.