[Cell biology and function of eosinophilic granulocytes in immunologic inflammation]

In recent years, increasing evidence has accumulated to suggest that the eosinophil represents a potent cytotoxic effector cell which plays a key role in the pathogenesis of pulmonary diseases as well as other human disorders. Beside contributing to antiparasitic host defense, eosinophils can prove detrimental to a number of host organs and tissues via release of their preformed basic proteins as well as de novo generated lipid mediators or oxygen radicals. Eosinophil effector functions are stimulated by certain lipid mediators and cytokines released by other cells in the course of active disease. In addition to their effector functions, eosinophils may have other functions in immune responses. Synthesis and expression of class II proteins of the major histocompatibility complex (MHC) may enable eosinophils to serve as antigen-presenting cells, i.e. to the antigens that appear at mucosal surfaces. In addition to collaborative interactions with lymphocytes, CD4-expressing eosinophils may elaborate cytokines that can effect cells within their tissue milieu. In conclusion, the evolving understanding of eosinophils indicates that eosinophils may not only serve as end-stage effector cells but also interact cooperatively with other cellular tissue elements in related diseases.