Human eosinophils elaborate the lymphocyte chemoattractants. IL-16 (lymphocyte chemoattractant factor) and RANTES

Eosinophils and CD4+ lymphocytes are preferentially recruited into sites of allergic inflammation. A role for eosinophils in the recruitment of CD4+ lymphocytes has not been defined. We studied the capacity of human eosinophils to release chemoattractants for T lymphocytes. Supernatants of cultured eosinophils contained chemoattractant activity for lymphocytes, which was predominantly due to IL-16 (lymphocyte chemoattractant factor) and RANTES. With neutralizing Abs, eosinophil-derived lymphocyte chemotactic activity was diminished by a mean (+/- SEM) of 60 +/- 3% with polygonal anti-IL-16 Ab, 69 +/- 4% with anti-IL-16 mAb, 48 +/- 3% with anti-CD4 F(ab) (IL-16 receptor blockade), 40 +/- 4% with anti-RANTES mAb, and 88 +/- 5% with a combination of anti-IL-16 and anti-RANTES mAbs. IL-16 and RANTES were detectable in eosinophil-derived supernatants by ELISA. Eosinophils constitutively expressed mRNA transcripts for both IL-16 and RANTES detectable by reverse transcription-PCR and contained preformed IL-16 and RANTES demonstrable by ELISA of cell lysates and by immunocytochemistry of freshly isolated eosinophils. Thus, eosinophils are a source of two cytokines, IL-16 and RANTES, that are chemoattractants for lymphocytes as well as eosinophils. These data indicate that eosinophils could contribute cytokines to enhance the recruitment of additional populations of CD4+ lymphocytes and eosinophils.