KL and antigen act in synergy to promote degranulation and transcription of cytokine genes. (A,B) Human mast cells were incubated overnight in the presence of antigen-specific IgE in the absence (deprived cells) or presence (nondeprived cells) of KL and IL-6. Cells were left unstimulated or stimulated with 100 ng/mL KL or antigen (Ag), individually or in combination. Release of the granule marker, β-hexosaminidase, was measured 15 minutes after addition of stimulants (A). Values are expressed as percent of intracellular β-hexosaminidase that was released into the medium and are the mean ± SEM from 6 separate experiments. For measurement of the cytokine mRNAs by an RNase protection assay, stimulation was stopped 2 hours after addition of KL or antigen (B). The blots shown are from 1 of 3 experiments. The expected positions of the cytokine mRNA probes are as indicated. (C,D) Cells were incubated overnight in the presence of IgE, KL, and IL-6 and then for 3 hours in the absence of growth factors. Cells were subsequently stimulated or not with antigen and KL for 16 hours for measurement of GM-CSF and IL-8 in the culture medium by ELISA. Values are mean ± SEM from 3 experiments and have been corrected for values in the absence of stimulants (ie, GM-CSF, 45 pg/106 cells; and IL-8, 380 pg/106 cells).
