Aryl Hydrocarbon Hydroxylase Activity in Subpopulations of Peripheral Blood Mononuclear Cells1

Peripheral blood mononuclear cells (PMC), isolated by density gradient techniques with Ficoll-Hypaque, contain Tand B-lymphocytes and monocytes. An/I hydrocarbon hydroxylase (AHH) activity was measured in PMC subtrac tions consisting of T-lymphocyte-enriched, T-lymphocytedepleted, and monocyte-depleted populations. The T-cellenriched populations consistently showed enhancement of AHH activity with both the fluorometric and radiometrie technique when compared to the total PMC population. This enhanced AHH activity was observed when the Tcell-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 tech nique before lymphocyte culture. T-cell-depleted popula tions (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 deplet ing 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.