Human skin mast cells rapidly release preformed and newly generated TNF-alpha and IL-8 following stimulation with anti-IgE and other secretagogues

Several groups have previously reported that rodent or human leukemic mast cells produce inflammatory cytokines such as TNF-alpha and IL-8 as well as the pro-allergic cytokines IL-4, IL-5 and IL-13. Comparatively little is kn own, however, regarding the ability of normal human skin mast cells to secr ete these factors following either IgE-dependent or IgE-independent modes o f activation. We therefore investigated whether normal human skin mast cell s produce these cytokines following stimulation by a variety of secretagogu es. Enriched isolated skin mast cells released both TNF-alpha and IL-8 foll owing activation with either anti-IgE, SCF, substance P compound 48/80 or A 23187. This release was dose- and time-dependent, with maximal levels being reached within 4 h of stimulation involving, in part, the secretion of pre formed stores of both cytokines. In accordance with this, using lysates of highly purified (>90%) skin mast cells, we could demonstrate that both TNF- alpha and IL-8 mRNA and protein were present in both unstimulated as well a s stimulated mast cells. In stark contrast to these results, no significant levels of either IL-4, IL-5 or IL-13 were detected, regardless of the secr etagogue used or the period of stimulation. These results show that human s kin mast cells are capable of rapidly secreting pro-inflammatory cytokines like TNF-alpha and IL-8 following IgE-dependent activation and stimulation by the neuropeptide substance P, SCF and the basic polypeptide analogue com pound 48/80. In contrast to other types of human mast cells however, human skin mast cells were incapable of secreting IL-4, IL-5 or IL-13 in these se ttings.