Naturally acquired anti-alpha Gal antibodies in a murine allograft model similar to delayed xenograft rejection

Antibodies directed against galactose-alpha 1,3-galactose (alpha Gal) are b elieved to play an important role in the pathogenesis of delayed xenograft rejection (DXR). This study was designed to determine whether alpha 1,3-gal actosyltransferase-deficient (Gal KO) mice can naturally acquire a sufficie nt anti-alpha Gal titre to cause the delayed type rejection of alpha Gal-ex pressing hearts. Gal KO mice of various ages were assessed for anti-alpha G al antibody levels. alpha Gal-expressing hearts were transplanted heterotop ically into these mice and monitored daily. Rejecting and surviving hearts were evaluated histologically. In Gal KO mice greater than 6-month-old, 64% had an anti-alpha Gal antibody titre above the background level. When wild -type alpha Gal-expressing hearts were transplanted into this group, 45% of grafts rejected within 5 to 13 days. Histological examination of the rejec ted hearts displayed marked tissue damage and an inflammatory infiltrate of predominantly macrophage/monocytes. Surviving grafts showed preserved morp hology. Like humans, Gal KO mice naturally develop anti-alpha Gal antibodie s with age. The titre in these mice was sufficient to cause a "delayed-type " rejection of a significant proportion of alpha Gal-expressing cardiac gra fts. This model thus provides an opportunity to investigate the role of nat urally acquired anti-alpha Gal antibodies in the pathogenesis of DXR.