Production of Interleukin-6 by Human Mast Cells and Basophilic Cells

Abstract

Since mast cells and basophils are thought to play a central role in several types of cutaneous inflammatory and allergic reactions, and since interleukin-6 (IL-6) is an important mediator in these processes, we have studied the ability of the human mast cell line HMC-1, the human basophilic cell line KU812, and human skin mast cells to produce IL-6. All three cell types proved to be potent sources of this cytokine after appropriate stimulation. Transcription of IL-6 mRNA was first detectable 2 h after stimulation with the ester phorbol myristate acetate (PMA) and the calcium ionophore A23187 in both cell lines, as evidenced by semiquantitative reverse transcriptase polymerase chain reaction analysis. Whereas resting cells did not produce IL-6 protein, PMA/A23187-stimulated cells released immunoreactive and biologically active IL-6, as demonstrated and quantitated by enzyme-linked immunosorbent assay and by the use of TEPC 1033 cells, an IL-6-dependent murine plasmacytoma cell line. Stimulated KU812 cells secreted sevenfold more IL-6 (up to 15 ng/ml) than HMC-1 cells (up to 2.4 ng/ml). Immunoblotting of HMC-1- and KU812 cell-derived IL-6 revealed several IL-6 forms in the molecular weight range of 21 to 30 kDa. Immunoelectron microscopic studies of human skin biopsies provided evidence that unstimulated mast cells do not contain preformed IL-6 but accumulate IL-6 in cytoplasmic and extruded granules after IgE-dependent stimulation. These findings suggest that IL-6 secreted by human mast cells and basophils potentially contributes to allergic, other immunologically mediated and nonspecific inflammatory responses.

Cytokine Production by Skin-Derived Mast Cells: Endogenous Proteases Are Responsible for Degradation of Cytokines

“…By immunohistochemistry, mast cells of the MC TC phenotype in skin as well as ocular and respiratory tissues appeared to contain IL-4 and IL-13, but little if any IL-5 and IL-6, whereas MC T cells contained IL-5 and IL-6 and lesser levels of IL-4 (9,10). In contrast, another study of human skin-derived mast cells showed IL-6 mRNA and protein production after stimulation (11). Skin-derived mast cells also produce IL-8 (12) and TNF-␣ (13); however, in this latter study, no IL-4, IL-5, or IL-13 was detected.…”

Identification of Antigen-Capturing Cells as Basophils

“…LPS (50 g/ml) was used as additional stimulus but did not result in a significant release of IL-4. These functional properties were very much reminiscent of the previously described IL-4-secreting non-B non-T cells (19) and raised the possibility that the cell population might consist of basophilic granulocytes that are know to release IL-4 after stimulation (20,21). Indeed, staining with Abs against IgE and the IL-3R (CD123) showed that all allophycocyanin-positive non-B cells were highly positive for both molecules (Fig.…”

Is there a role for mast cells in psoriasis?

“…In addition, IL-4-positive mast cells are signiWcantly associated with the size of allergic skin prick-test wheal reaction and serum total IgE levels [156]. Even though human mast cells have been shown to express IL-6 and TGF-1 [88,99]; it is, however, not known to what extent mast cells contain these Th17 priming cytokines in the psoriatic skin. Our preliminary results suggest that mast cells contain IL-6 immunoreactivity in the developing psoriatic lesion induced by the tape-stripping technique (Suttle et al, unpublished results) (Fig.…”