T lymphocytes in atopic children.

The number of circulating T and B cells and the sensitivity of lymphocytes to stimulation with phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweek mitogen (PWM) was studied in 233 atopic children. The number of T lymphocytes was found to be decreased in cases of rhinoconjunctivitis, asthma as well as atopic eczema. Levels of B lymphocytes were normal. Sensitivity to stimulation with PHA and to a lesser degree, Con A, was significantly decreased whereas stimulation with PWM was unaffected. The severity of the atopic eczema was inversely correlated to T cell numbers. Several lines of evidence indicated that the abnormalities observed were intrinsically associated with the atopic conditions and not evoked by corticosteroid treatment. The results are compatible with the hypothesis that atopy is associated with a defect of a subpopulation of T cells. The possibility that this subpopulation has a suppressor function on reagin formation is discussed.