HUMAN C1Q INDUCES EOSINOPHIL MIGRATION

Eosinophils (Eo) play a significant role in allergic inflammation and the host's immunity to parasitic infections. Although the presence of Clq-binding cell surface molecule(s) (C1q-R) on Eo had been previously implicated by the ability of Clq to augment IgG-dependent, Eo-mediate d killing of schistosomula, little is known about the structure or the function of this receptor. The present studies were therefore underta ken to immunochemically demonstrate and to examine the biology of Eo C 1q-R, Eo were purified to homogeneity (>90%) and viability (>98%) from hypereosinophilic donors by Percoll density gradient. Western blot an alysis using antibodies to cC1q-R and gC1q-R showed distinct bands cor responding to cC1q-R (60 kDa) and gC1q-R (33 kDa) when immunoblotted w ith their respective antibodies. The Eo C1q-R was tested for its abili ty to induce chemokinesis and/or chemotaxis as assessed by the modifie d Boyden microchamber assay utilizing 5-mu m-pore polycarbonate membra nes and using C1q, cC1q, or gC1q (10 mu g/ml) as agonists. The known c hemotactic factors C5a and RANTES (10(-8) M) were used as positive con trols, The results showed that at this concentration, cC1q was most ef ficient in its ability to induce Eo migration (20 +/- SEM 12, n = 4) f ollowed by Clq (107 +/- SEM 7, n = 7) and gC1q (77 +/- SEM 10, n = 10) , When checkerboard analysis was performed, the data indicated that th e observed phenomenon was likely to be due largely to chemokinesis, As expected, C5a (145 +/- SEM 15, n = 7) and RANTES (145 +/- SEM 43, n = 7) were both chemotactic. Furthermore, incubation of Eo with 50 mu g of either C1q, gC1q, or cC1q (1 hr, 37 degrees C) did not cause releas e of eosinophil cationic protein as measured by RIA, nor did it enhanc e the expression of CD11b or CD29 as assessed by FAGS analysis, The da ta presented in this paper show that Eo express both cC1q-R and gC1q-R and may participate in Eo function by providing a primary signal for locomotion. (C) 1996 Academic Press, Inc.