Pulmonary intravascular macrophages: a review of immune properties and functions.

Pulmonary intravascular macrophages (PIMs) are mononuclear cells found apposed to the lung capillary endothelium in a number of mammalian species. Although first described in the 1970s, it was not until the 1980s that they were more completely described. In several species of veterinary interest (bovine, porcine, ovine, and feline), PIMs are very important in blood clearance, which is not the case in mice and rats. Only recently have the immunological activities of PIMs been verified. In this review, we present an overview of PIM research with particular emphasis on the immune functions of this highly reactive macrophage population.