Cell-adhesion molecules expressed by activated eosinophils in Onchocerca volvulus infection.

Cell-adhesion receptors mediate the interaction between host effector cells and cellular or multicellular targets, including opsonized parasites. Our recent finding of a deposition of plasma proteins, including fibronectin, on the surface of infective larvae of the helminthic parasite Onchocerca volvulus led us to investigate the possible expression of cell-adhesion molecules (CAM), particularly fibronectin receptors, on eosinophilic granulocytes from persons infected with O. volvulus. Immunofluorescence analyses showed that freshly isolated eosinophils strongly expressed the beta 2-integrin CR3 and exhibited to a lower degree CR4 and the integrin-associated carbohydrate determinant Le(x), as well as antigen p24 (CD9). Eosinophils exposed to the eosinophil-active cytokines recombinant human interleukin 3 (rhIL-3) and granulocyte/macrophage colony-stimulating factor (rhGM-CSF) in addition to CR3, CR4, and CD9 expressed the beta 1-integrins VLA-4 and to a lesser extent VL-5 (both fibronectin receptors) as well as the intercellular adhesion molecule ICAM-1. Low-level expression of these adhesins was also observed on eosinophils cultured in the presence of these interleukins on confluent fibroblasts. The presence of VLA-4 as well as VLA-5 on activated eosinophils was confirmed by demonstration of the formation of immune rosettes using antibody-coated microspheres and by their attachment to fibronectin-coated surfaces. These results indicate the possibility of an involvement of previously unidentified antibody- and complement-independent mechanisms in cellular interactions with the parasite O. volvulus.