INTERACTION OF ANTIBODY WITH FORSSMAN ANTIGEN IN GUINEA-PIGS - A MECHANISM OF ADAPTATION TO ANTIBODY-MEDIATED AND COMPLEMENT-MEDIATED INJURY

Forssman antigen is a glycosphingolipid with antigenic specificity det ermined by extra-membrane haptenic sugars similar to blood group antig ens and antigens that are the main barrier to xeno-geneic organ transp lantation. Herein, we describe the localization of Forssman antigen in guinea pig lungs and kidneys and the consequences of its interaction with antibodies in vitro and in vivo (Forssmas reaction). Exposure of cultured guinea Pig aortic endothelial cells to Forssman antibodies in duced rapid redistribution of antigen-antibody complexes at the cell s urface, followed by shedding that occurred by blebbing of plasma membr ane as vesicles or fragments, and was associated with disappearance of antigen from the cell surface (antigenic modulation). Guinea pigs sur viving frequent intravenous injections of increasing amounts of antibo dies, for a total of 20 to 40 lethal doses, developed a partial or com plete adaptation to generalized Forssman reaction, and adaptation was associated with partial or complete modulation of Forssman antigen at the surface of the pulmonary and in minor degree, renal endothelial an d epithelial cells. These findings support the hypothesis that modulat ion of endothelial carbohydrate antigens contributes to adaptation of highly vascularized organs exposed to tolerable levels of allo- or xen o-antibodies.