Protection from complement-mediated injury in livers and kidneys of transgenic mice expressing human complement regulators

The major problem in the use of phylogenetically distant donors is a fast, strong reaction called hyperacute rejection. This reaction mediated by complement is directed against the vascular endothelia of the transplanted organ. Complement activation is tightly controlled by several regulatory proteins which inhibit the formation and function of different complement components. To verify the hypothesis that organs expressing such inhibitory factors could be spared from complement-mediated hyperacute rejection, we have generated mice transgenic for the human complement inhibitor membrane cofactor protein (hMCP) and decay accelerating factor (hDAF). Different levels of hMCP and/or hDAF expression, according to the promoter used, were detected by RNA analysis in the major organs, specifically on the organ vascular endothelia, as revealed by immunohistochemical analysis. The development of an in vivo model of human plasma perfusion allowed the characterization of complement-mediated damage in control animals and the degree of protection due to the presence of hMCP, hDAF, or both in the organs derived from single or double transgenic mice. In this paper we compare the level of expression of complement regulators with the degree of protection in two major organs: liver and kidney.