Studies on the enhancement of human eosinophil function by mononuclear cell products in vitro

Previous studies have shown that human mononuclear cells produce during culture an activity that enhances the functional properties of mature eosinophils, including their helminthotoxic potential (Veith & Butterworth, 1983). We have now found that the enhancing activity in mononuclear cell culture supernatants (MCS) is stable to dialysis for 24 h at pH 2 and sensitive to trypsin (0.1 mg/ml). It has a principal pI of 4.4 and possible secondary peaks with pI values of 5.0 and 5.7. The effect of MCS on eosinophils appears to be a general early stimulation of several functions. In comparison with eosinophils incubated in medium only, the proportion of eosinophils with Fc receptors is increased after incubation with MCS for 3.5 h (39 +/- 11% vs 16 +/- 3%) and 7 h (28 +/- 4% vs 17 +/- 3%). The temperature-dependent phase of eosinophil adherence to antibody coated schistosomula is enhanced after 3-4 h. The uptake of deoxyglucose is enhanced after a 1 h pre-incubation with MCS (24 +/- 1 X 10(3) d/min), compared with that of controls (15 +/- 2 X 10(3) d/min). Whether these effects are due to one mediator in MCS awaits further investigation.