2001 OPEN FORUM Abstracts
HUMAN PERIPHERALBLOOD EOSINOPHILS EXPRESS STEM CELL FACTOR
Mor-Li Hartman Ph.D*, AdrianM. Piliponsk,,* Vladislav Temkin*, Francesca Levi-Schaffer*, Ph.D. Departmentof Pharmacology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
*Current Post-doctoral fellow,Department of Pathology, Beth Israel Deaconess Medical Center, Boston, MA
Stem cell factor (SCF) or c-Kit ligandis a cytokine associated with the differentiation, survival, and activationof mast cells. Eosinophils have pleiotropic functions in several diseases and,together with mast cells, are key cells in allergy. Mast cell-eosinophil interactionscan take place during the late and chronic phases of allergy. It was, therefore,investigated whether eosinophils can produce SCF and consequently influencemast cells. Human peripheral blood eosinophils variably expressed mRNA for thesoluble and uncleaved forms of SCF (reverse transcription-polymerase chain reaction)and produced the 18.5-kd protein backbone of SCF (Western blot analysis). Afterovernight incubation in medium, eosinophils also produced SCF of higher molecularweight (42-45 kd) that might represent its glycosylated forms. Eosinophils expressedcytoplasmic SCF that colocalized with major basic protein (confocal laser microscopy).Freshly isolated eosinophils contained 8.9 ± 1.7 pg SCF/106 (mean± SEM; enzyme-linked immunosorbent assay). Although overnight incubation ofthe eosinophils in either culture medium or in phorbol 12-myristate 13-acetate-calciumionophore did not cause the secretion of SCF, the addition of chymase inducedSCF release. In summary, it was demonstrated that human peripheral blood eosinophilsare a source of SCF. These results may contribute to a better understandingof the interactions between eosinophils and mast cells in allergic inflammation.