Aryl hydrocarbon hydroxylase activity in subpopulations of peripheral blood mononuclear cells

Peripheral blood mononuclear cells (PMC), isolated by density gradient techniques with Ficoll-Hypaque, contain T- and B-lymphocytes and monocytes. Aryl hydrocarbon hydroxylase (AHH) activity was measured in PMC subfractions consisting of T-lymphocyte-enriched, T-lymphocyte-depleted, and monocyte-depleted populations. The T-cell-enriched populations consistently showed enhancement of AHH activity with both the fluorometric and radiometric technique when compared to the total PMC population. This enhanced AHH activity was observed when T-cell-enriched populations were isolated either before or after 96 hr of lymphocyte culture, by the sheep red blood cell rosette method, or by the nylon wool column technique before lymphocyte culture. T-cell-depleted populations (B-cell enriched) obtained by sheep red blood cell rosette method had diminished AHH activity. Monocytes were shown to contribute to the total PMC AHH activity through an indirect technique by first depleting the monocytes from PMC with the carbonyl iron method. The monocyte-depleted populations had less AHH activity than did the total PMC population after both 24 and 96 hr of culture. The greatest amount of AHH activity was present in PMC populations with their native number of monocytes when cultured for 96 hr in the presence of mitogens.