A case of acquired hypogammaglobulinaemia has been examined. Total and differential leucocyte counts and distribution were normal as were the lymphocyte sub-populations when defined by surface membrane immunoglobulin, E-, EA- and EAC-rosette techniques. The proliferative response of unseparated lymphocytes to PHA and Con-A was normal while the response to PWM was clearly impaired. In contrast, testing of purified B-lymphocytes by PWM was within the normal range. The response to PWM was found to be depressed by adding the patient's T-lymphocytes to autologous B-lymphocytes as well as to B-lymphocytes from 10 normal, healthy controls. The patient's T-lymphocytes were further tested for cytotoxicity against autologous. B-lymphocytes and B-lymphocytes from the 10 control individuals. Cytotoxicity was observed against autologous B-lymphocytes and against the B-lymphocytes of 3 controls. These findings indicate the presence of peripherally circulating unspecific T-suppressor lymphocytes and cytotoxic T-lymphocytes of some immunogenetic specificity. The suppressor and cytotoxic T-lymphocytes may separately or in combination be involved in the pathogenesis of hypogammaglobulinaemia. Thus, these findings are equivocal but underline the immunologic aspects of the pathogenesis.
