IGE-DEPENDENT EXPRESSION OF MESSENGER-RNA FOR IL-4 AND IL-5 IN HUMAN LUNG MAST-CELLS

By using the reverse transcriptase (RT)-PCR and in situ hybridization we have studied the expression of mRNA for IL-5 and IL-4 in human lung mast cells induced by cross-linkage of high affinity Fc epsilon Rs. L ung mast cells were purified using affinity magnetic selection with mA b YB5.B8 against c-kit to achieve a final mast cell purity >93%. Purif ied mast cells were precultured with stem cell factor (SCF) (10 ng/ml) and myeloma IgE (3 mu g/ml) for 16 h before challenge with anti-IgE(1 or 10 mu g/ml). IgE-dependent activation of lung mast cells caused ex pression of IL-5 mRNA, which was evident by 2 h and persisted for up t o 48 similar to 72 h in all of 12 experiments, whereas IL-4 mRNA expre ssion was of a shorter duration and was demonstrable in 6 of 13 experi ments. We confirmed that mast cells, and not T cells, were the source of these cytokine messages by using reverse transcriptase-PCR in cell preparations containing known numbers of mast cells and T cells, in si tu hybridization in enriched mast cell preparations, and double in sit u hybridization-immunocytochemical staining. IL-5 mRNA expression did not require the pretreatment of cells with SCF, whereas expression of IL-4 mRNA seemed to require both anti-IgE and SCF. The strength of IL- 5 mRNA signal was related to anti-IgE concentration. Immunoreactive IL -5 was detectable 8 h after anti-IgE challenge, and 10(6) mast cells g enerated a mean of 731 +/- 400 pg of IL-5 into the supernatant during 48-h culture, but no IL-4 product was detectable. These findings demon strate the capacity of human lung mast cells to transcribe IL-4 and IL -5 after IgE-dependent activation and to synthesize and release immuno reactive IL-5.