ENHANCEMENT BY STEM-CELL FACTOR OF INTERLEUKIN-2 (IL-2)-INDUCED DNA-SYNTHESIS IN HUMAN DECIDUAL CD16(-)CD56(BRIGHT) NATURAL-KILLER-CELLS MEDIATED BY INCREASED EXPRESSION OF THE IL-2 RECEPTOR-ALPHA CHAIN

Extracts of chorionic villous and decidual tissue specimens from women in the early stages of pregnancy contained stem cell factor (SCF), th e amount in the latter tissue (246.6 +/- 119.7 pg/mg protein) bring ap proximately three times that in the former. Immunohistochemical analys is revealed the presence of SCF in the mesenchymal cells of the chorio n, the trophoblast, and decidual stromal cells, whereas the SCF recept or, c-kit, was detected in the trophoblast and decidual mononuclear le ukocytes but not in decidual stromal cells. Reverse transcription and polymerase chain reaction analysis detected transcripts corresponding to both secretory and membrane-bound types of SCF in chorionic tissue, but only those encoding the secretory type in decidual tissue. Flow c ytometric analysis showed that c-kit was expressed on decidual CD16 (- ) CD56(bright) natural killer (NK) cells, CD14(+) macrophages, and CD3 4(+) hematopoietic progenitor cells, but not on CD3(+) T cells or CD16 (+) NK cells. Although SCF alone had no effect on DNA synthesis in dec idual CD16(-)CD56(bright) NK cells, it enhanced the proliferative effe ct of interleukin-2 (IL-2) at IL-2 concentrations that selectively sat urate the high-affinity IL-2 receptor (IL-2R). Flow cytometry of decid ual mononuclear leukocytes cultured in the presence of SCF demonstrate d that this factor increased the expression of the: IL-2R alpha chain, but not IL-2R beta and gamma chain expression on CD16(-)CD56(bright) NK cells. Results suggest that SCF produced in the decidua increases t he expression of the IL-2R alpha which is usually present in smaller a mounts than other two IL-2R chains on decidual CD16 CD56(bright) NK ce lls, and thereby promotes the proliferation of these cells in response to low concentrations of IL-2, resulting in an increase of the high a ffinity IL-2Rs. (C) 1998 Elsevier Science Ireland Ltd. All rights rese rved.