CONSTITUTIVE EXPRESSION OF INTERFERON GAMMA-INDUCIBLE PROTEIN-10 IN LYMPHOID ORGANS AND INDUCIBLE EXPRESSION IN T-CELLS AND THYMOCYTES

Interferon gamma-inducible protein 10 (IP-10), a member of a family of small proinflammatory chemotactic polypeptides, is expressed in inter feron gamma-stimulated keratinocytes, macrophages, fibroblasts, and en dothelial cells. Here we report that IP-10 is also expressed by activa ted but not resting T hybridoma cells, normal T cells, and thymocytes. Although resting lymphocytes did not synthesize IP-10, surprisingly h igh levels of IP-10 transcripts were found in lymphoid organs (spleen, thymus, and lymph nodes). Thymic and splenic stromal cells were found to express constitutively high levels of both IP-10 mRNA and protein, accounting for the high level of spontaneous expression in lymphoid t issue. Therefore, in addition to its role as a proinflammatory cytokin e, IP-10 may participate in T cell effector function and perhaps T cel l development.