FH regulation of complement involves interacting with the host cell on the carboxyl terminal domains and interacting with complement C3b and FI on the amino terminal of the protein. This interaction results in inactivation of C3b (iC3b), prevention of host cell lysis and inflammation, and prevention of complement-mediated micro- and macrothrombotic angiopathies. A mutation on the carboxyl end of FH at W1206R (W1183R in human) results in a loss of host cell contact by FH without affecting regulation of complement. This loss of host cell interaction appears to result in a multiorgan thrombotic angiopathy, including stroke, retinopathy, and TMA, which leads to renal failure.