ALTERED EXPRESSION OF CD11B AND CD62L AFTER CROSS-LINKING OF CD45 ISOFORMS ON HUMAN EOSINOPHILS

Background: Phosphotyrosine phosphatase CD45 is exclusively found on n ucleated hematopoietic cells, CD45 is an essential component of signal ing of mast eel degranulation and of lymphocyte activation? but little is known about its role in eosinophils, In the present study, we have determined the expression and function of CD45 isoforms on human eosi nophils. Methods: Expression of CD45 isoforms on purified peripheral b lood eosinophils was examined using indirect immunofluorescence and fl ow cytometry. Eosinophils were cultured with anti-CD45 isoform monoclo nal antibodies (mAbs) for up to 24 h, Eosinophil activation was evalua ted by measuring surface expression of CD11b or CD62L by flow cytometr y. Results: Fresh eosinophils express CD45, CD45RB, CD45RO epitopes bu t not CD45RA, Incubation with anti-CD45 isoform mAb for 30 min did not alter the expression of either CD11b or CD62L on eosinophils. In cont rast, the expression of CD11b was significantly enhanced after 24 h of incubation with mAbs against CD45, CD45RB, or CD45RO, In addition, th e expression of CD62L was also significantly reduced with anti-CD45RB and with anti-CD45RO mAbs. Conclusions: Cross-linking of surface CD45 isoforms for 24 h significantly induced upregulation of CD11b expressi on and CD62L shedding, consistent with activation of eosinophils, Our data suggest that CD45 isoforms are functionally expressed on human eo sinophils, and are capable of modulating eosinophil function and might participate in allergic inflammation.