Comparison of antileukemic immunity against U937 cells in atopic asthmatics versus healthy controls

To assess the antitumor effects in atopic asthmatics versus healthy adults, we designed this study using in vitro mononuclear cells (MNC) culture as an immunity model with human leukemic U937 cells as the target. MNCs were collected from asthmatic subjects and healthy controls. Conditioned media from the MNC cultures (MNC-CM) were collected after stimulation with various concentrations of phytohemagglutinin (PHA). We treated U937 cells with these MNC-CMs, then assayed their proliferation and differentiation after 5 days of culture. At lower PHA doses (1.25 microg/ml), as well as in absence of PHA, the asthmatic MNC-CMs inhibited U937 cells growth to a slightly greater extent than did the MNC-CMs from controls. In contrast, when higher doses of PHA were used (5, 10 microg/ml), this growth-inhibiting effect was dramatically reversed. The dual effect of MNC-CM in these two groups was also shown in U937 cell differentiation assay, assessed as follows: morphological change by Liu's staining, functional change by NBT reduction test and CD 14 expression by flow cytometric detection. We suggest that the antileukemic effects of MNCs from asthmatic patients result from a slightly immunopotentiated status. This immunity may be dramatically reversed, however, after marked activation of MNCs.