Accumulation of inflammatory cells in response to intracutaneous platelet activating factor (Paf-acether) in man

Platelet activating factor (Paf-acether, AGEPC) is a family of ether-linked phospholipids known to be released from a range of inflammatory cell types. In vitro and in experimental animals, it seems to be a mediator of inflammation, and intradermal injection of Paf-acether in man elicits a biphasic inflammatory response, reminiscent of the dual response to allergen in sensitized individuals. In the present study, cutaneous histology was assessed in sequential skin biopsies from six normal volunteers after intradermal injection of 200 or 800 pmol Paf-acether. Paf-acether (200 pmol) induced intravascular accumulation of neutrophils, accompanied by a perivascular mixed cellular infiltrate which was composed predominantly of neutrophils at 4 and 12 hours, and lymphocytes and histiocytes at 24 hours. Control injections of lyso-Paf and normal saline induced no noteworthy histological changes. Paf-acether (800 pmol) resulted in vessel destruction, gross endothelial swelling and a perivascular infiltrate of mononuclear cells and neutrophils, accompanied by occasional evidence of leucocytoclasis. By virtue of its ability to induce inflammatory cell accumulation in human skin, Paf-acether should be considered as a potential mediator of inflammatory disorders such as psoriasis.