Serial study of T lymphocytes in childhood leukemia during remission.

Peripheral blood T lymphocyte numbers and function were studied in 22 children on UKALL X maintenance chemotherapy over a 2-year period, and results were compared with 20 healthy children. CD4 and CD8 subsets were enumerated using indirect immunofluorescence, and specific (HSV-1) and polyclonal (Con A, PWM) activation was studied by proliferation and IL-2/IL-4 production in vitro. T lymphocytes were significantly decreased with a greater fall in CD4 than CD8 T lymphocyte numbers. Proliferation responses were slightly but significantly decreased whereas IL-2 and IL-4 production were not significantly different from control values. These findings suggest that decreased numbers of CD4 helper T cells may be the most important factor in clinical immunodeficiency during maintenance chemotherapy for cALL contributing to increased susceptibility to opportunistic infections and argue against the presence of T lymphocytes with defective function.