CELLULAR-LOCALIZATION OF INTERLEUKIN-5 EXPRESSION IN RECTAL-CARCINOMAWITH EOSINOPHILIA

Eosinophilia often occurs in malignant diseases. This report concerns a female patient aged 76 pears, diagnosed with rectal carcinoma with e osionophilia. Sera were obtained at two different periods (at diagnosi s and after the operation) for the evaluation of levels of interleukin -5 (IL-5). The serum IL-5 level increased to 264 pg/mL, and returned t o an undetectable level after the operation. The serum at diagnosis en hanced the viability of normal eosinophils in vitro, and this activity nas inhibited by antihuman IL-5 polyclonal antibody. Immunohistochemi stry and in situ hybridization revealed that stromal eosinophils conta ined IL-5 protein and messenger RNA (mRNA), but no IL-5 transcripts we re detected in eosinophils attached to carcinoma cells. In situ detect ion of apoptosis showed that several eosinophils attached to tumor cel ls underwent apoptosis and lost their eosinophil secreted cationic pro tein ((ECP) and major basic protein (MBP). These results map suggest t hat activated eosinophils by IL-5 play an important role in host defen se mechanisms, releasing their toxic granule proteins on adjoining tum or cells. Copyright (C) 1998 by W.B. Saunders Company.