DEFENSINS - MICROBICIDAL AND CYTOTOXIC PEPTIDES OF MAMMALIAN HOST DEFENSE CELLS

Multicellular organisms contain specialized cells (granulocytes, macrophages, cytotoxic lymphocytes, natural killer cells, etc.) that can selectively destroy invading microbes, larger parasites, and abnormal or senescent host cells. All cells that manifest microbicidal/cytotoxic activity contain cytoplasmic granules that are released on contact onto the appropriate target. Analysis of these granules has shown that they contain a variety of lytic enzymes and microbicidal or cytotoxic proteins. Although it is by no means certain how individual microbicidal and cytotoxic proteins contribute to the destruction of their targets, the ability of these proteins to permeabilize biological membranes appears to be a common theme. The granules of neutrophils, eosinophils, and killer lymphocytes have been particularly rich sources of such proteins. This review is focussed on defensins, small and highly abundant microbicial and cytotoxic peptides of mammalian phagocytes.