Local production of interleukin-5 by T lymphocytes is associated with recruitment of eosinophils in patients with eosinophilic granuloma of the soft tissue.

Abstract

Eosinophilic granuloma of the soft tissue (EOSG) is a rare disease of unknown cause. Since the in vivo mechanism of eosinophilia remains unclear, the present study was performed to investigate the mechanism of the infiltration of eosinophils into the granuloma tissue. Immunohistochemical techniques and an eosinophil chemotactic assay were used in analysis. Peripheral blood eosinophils obtained from one patient showed an increased chemotactic response against tissue extract that was inhibited by pretreatment with anti-IL-5 antibodies. Eosinophils obtained from the peripheral blood of patients with EOSG showed a significant increase in chemotactic activity toward 10(-9) M recombinant human (rh) IL-5 versus that of healthy individuals, whereas eosinophils from granuloma tissue showed no chemotactic response toward rhIL-5, indicating that IL-5 may deactivate the eosinophils. Immunohistochemical studies showed that CD4+ cells were predominantly found in the extrafollicular region, along with interleukin-5+ (IL-5) cells. Staining of the adjacent 3-micrometers sections for CD3, eosinophils, and IL-5 revealed that most of the IL-5 immunoreactive CD3+ cells exhibited cytoplasmic staining. Conversely, 97% of IL-5+ eosinophils were stained peripherally in a ring-like manner, suggesting that IL-5 was bound to its cell surface receptor on the eosinophil. IL-5 mRNA expression was detectable in the CD3+T lymphocytes but not in eosinophils from granuloma tissue. These findings suggest that locally produced IL-5 from T lymphocytes may enhance the infiltration of eosinophils into the eosinophilic granuloma.