(T cells/cytokine superfamily/chemotaxis/monocyte/cytoplasmic free calcium)

The human cytokine 1-309 is a small glyco- protein secreted by activated T lymphocytes and structurally related to a number of inflammatory cytokines. To investigate the biological activities of 1-309 protein, we produced a stable Chinese hamster ovary cell transfectant, CDI.10, which con- stitutively secretes 1-309 protein into culture supernatant. Affinity chromatography on a heparin-Sepharose matrix fol- lowed by reverse-phase HPLC was used to purify to homoge- neity a glycoprotein doublet of 15-16 kDa from culture super- natant. Biochemical analysis showed the purified recombinant 1-309 glycoprotein to be indistinguishable from the natural 1-309 glycoprotein constitutively secreted by the T-cell line IDP2. Purifiled recombinant 1-309 stimulated migration of human monocytes but not neutrophils when tested by in vitro chemotaxis assay. Furthermore, the purifiled protein tran- siently increased cytoplasmic free calcium concentration in human peripheral blood monocytes but did not do so in lymphocytes or neutrophils. These results demonstrate that the 1-309 gene encodes an inflammatory mediator that specifically stimulates human monocytes.