T-lymphocyte subpopulations in relation to immunosuppression in measles and varicella.

Patients with measles or varicella were studied during the acute phase (first week) of illness and, after recovery, by lymphocyte stimulation tests and determination of T-lymphocyte subpopulations, using the monoclonal antibodies Leu 2a and Leu 3a directed at the suppressor/cytotoxic and the helper T-cell subsets, respectively. Low proliferative responses to phytohemagglutinin were found during the acute phase of both diseases. The response to purified protein derivate of tuberculin was also low in all measles patients tested and in some of the varicella patients. In both infections increased spontaneous DNA synthesis was demonstrated. In the acute phase of measles there was T lymphocytopenia but no change of the ratio between T lymphocytes of helper and suppressor/cytotoxic cell phenotypes. In the acute phase of varicella the percentage and the absolute number of Leu 2-positive (suppressor/cytotoxic) T cells were increased. Measurement of the size of the lymphocytes indicated activation of this subset. Cryopreserved blood mononuclear cells from the acute phase of varicella could suppress the phytohemagglutinin response of autologous convalescent-phase cells. This was not seen when cells from measles patients were tested. The suppression of the lymphocyte stimulation response in varicella is probably in part caused by activation of suppressor cells, whereas the suppression of the stimulation response in measles seems to be due mainly to other mechanisms.