[Eosinophils: protection or pathology: a cell with two personalities]

Expression of various membrane receptors on human eosinophils for immunoglobulin, complement, certain cytokines and chemotaxis factors, and adherence molecules as well as CD4 and class II major histocompatibility complex antigens has led to a reconsideration of the role of the eosinophil in the immune response. Eosinophils are able to present antigen and become infected by HIV. Eosinophils are not to only source of cytotoxic and proinflammatory mediators but can also release different cytokines and growth factors including their own differentiation factors. The recent demonstration that eosinophils can express IgE-binding molecules belonging to different multigenic families as well as two different IgA receptors which participate equally to the protective and to the pathological inflammatory responses reinforces the concept of a dual functionality for the eosinophil.