P. Welker et al., Human mast cells produce and differentially express both soluble and membrane-bound stem cell factor, SC J IMMUN, 49(5), 1999, pp. 495-500
Stem cell factor (SCF), characterized as mast cell growth factor, is known
to be produced by fibroblasts, keratinocytes and endothelial cells. Two dif
ferent splice variants encode for either a soluble (SCF-1) or a membrane-bo
und (SCF-2) form. In order to explore whether mast cells themselves can pro
duce SCF, we examined cultured cord blood (CBMC) and peripheral-blood-deriv
ed mast cells (PBMC), mast/basophil cell lines (HMC-1 and KU-812), and skin
mast cells for SCF expression. On immunocytochemistry, cytoplasmatic SCF-r
eactivity was observed in HMC-1 cells, with additional cell membrane staini
ng in KU-812, skin and cultured mast cells. Low amounts of SCF could be det
ected by ELISA in lysates of isolated and unstimulated mast cells and in su
pernatants of skin cells stimulated with anti-IgE or Ca-ionophore A23187. S
CF mRNA was detected in all cells, although marked quantitative differences
were observed among the various cell types. SCF-2 mRNA expression was low
in HMC-1 cells while it was marked in skin mast cells, KU-812 cells, CBMC a
nd PBMC. A time-dependent, increasing induction of both SCF forms was seen
in CBMC and PBMC during culture. After stimulation with A23187 and phorbol
myristate acetate, an up-regulation of SCF mRNA was noted in HMC-1 and KU-8
12 cells, without changes in the relationship of the two splice variants. T
he differential expression of SCF-specific mRNA splice variants in immature
and mature human mast cells and the secretion of this molecule by these ce
lls may play a role in autocrine stimulation, maintenance of survival and t
he differentiation of tissue mast cells.