IL-6 attenuates apoptosis, while neither IL-6 nor IL-10 affect the numbersor protease phenotype of fetal liver-derived human mast cells

Background The combination of recombinant human stem cell factor (rhSCF), r h interleukin (IL)-6 and rhIL-10 was reported to be optimal for mast cell d evelopment from cord blood progenitors and to induce chymase expression in all such mast cells earlier in their development than tryptase. Objective The effects of rhIL-6 and rhIL-10 in various combinations on the rhSCF-dependent development of human mast cells from fetal liver progenitor s were examined in serum-free media. Methods Dispersed fetal liver cells were cultured in serum-free AIM-V mediu m with rhSCF alone, or with combinations of rhIL-6 and rhIL-10. Tryptase an d chymase expression, surface Kit expression, metachromasia with toluidine blue and apoptosis were measured. Results Neither rhIL-6 nor rhIL-10 nor the two interleukins together, when included from day 0 of culture, affected the number or protease phenotype o f mast cells at 1 or 3 weeks. Expression of tryptase paralleled the appeara nce of metachromasia and surface Kit, both of which preceded chymase expres sion, regardless whether a rabbit polyclonal or mouse monoclonal anti-chyma se antibody preparation was used. On the other hand, rhIL-6 markedly attenu ated baseline levels of apoptosis in the presence of rhSCF as well as apopt osis occurring after withdrawal of rhSCF, whereas rhIL-10 had no effect. Conclusion RhIL-6 protected fetal liver-derived mast cells from apoptosis, particularly after withdrawal of rhSCF, but neither rhIL-6 nor rhIL-10 nor the combination of these interleukins affected the numbers or protease phen otype of these mast cells.