Characterization of a keratinocyte-derived T cell growth factor distinct from interleukin 2 and B cell stimulatory factor 1.

Epidermal epithelial cells (keratinocytes) produce and secrete a variety of immunologically active cytokines. We have previously reported that both transformed (PAM 212) and normal murine keratinocytes produce a soluble factor which induces proliferation of the T cell line, HT-2. In the present study we sought to compare keratinocyte-derived T cell growth factor (KTGF) with other T cell growth factors, characterize its physicochemical properties, and substantially purify KTGF from PAM 212 conditioned medium. KTGF from PAM 212 conditioned medium was not inhibited by antibodies which block the effect of interleukin 2 (IL 2) (S4B6) or B cell stimulatory factor 1 (BSF 1) (11B11). KTGF is heat-stable, has an isoelectric point of 4.8, and a relative molecular mass of 16 to 23 kilodaltons under nonreducing conditions. KTGF activity was enhanced at least 41,413-fold by sequential hydroxylapatite bulk preparation, desalting by reversed-phase chromatography, gel filtration high pressure liquid chromatography (HPLC), and reversed-phase HPLC. Keratinocytes produce a T cell growth factor with physicochemical properties distinct from IL 2 and BSF 1. KTGF may play a role in regulating the growth and differentiation of T cells in the epidermis.