The use of: (a) a complement Factor H polypeptide or an isolated cell expressing a complement Factor H polypeptide in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH polypeptide comprises isoleucine at a position corresponding to position 62 of SEQ ID NO:2 and tyrosine at a position corresponding to position 402 of SEQ ID NO:2; (b) a polynucleotide comprising a sequence encoding a CFH polypeptide, said sequence operably linked to a promoter in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH polypeptide comprises isoleucine at a position corresponding to position 62 of SEQ ID NO:2 and tyrosine at a position corresponding to position 402 of SEQ ID NO:2; (c) a complement Factor H-related 5 (CFHR5) polypeptide or an isolated cell expressing a complement Factor H-related 5 (CFHR5) polypeptide in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 polypeptide comprises proline at a position corresponding to position 46 of SEQ ID NO:8; (d) a polynucleotide comprising a sequence encoding a CFHR5 polypeptide, said sequence operably linked to a promoter in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 polypeptide comprises proline at a position corresponding to position 46 of SEQ ID NO:8; (e) an agent that reduces expression of a CFH variant polypeptide associated with increased risk of developing membranoproliferative glomerulonephritis type II (MPGNII) in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH variant polypeptide comprises histidine at a position corresponding to position 402 of SEQ ID NO:2; or (f) an agent that reduces expression of a CFHR5 variant polypeptide associated with increased risk of developing MPGNII in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 variant polypeptide comprises serine at a position corresponding to position 46 of SEQ ID NO:8. (a) a complement Factor H polypeptide or an isolated cell expressing a complement Factor H polypeptide in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH polypeptide comprises isoleucine at a position corresponding to position 62 of SEQ ID NO:2 and tyrosine at a position corresponding to position 402 of SEQ ID NO:2; (b) a polynucleotide comprising a sequence encoding a CFH polypeptide, said sequence operably linked to a promoter in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH polypeptide comprises isoleucine at a position corresponding to position 62 of SEQ ID NO:2 and tyrosine at a position corresponding to position 402 of SEQ ID NO:2; (c) a complement Factor H-related 5 (CFHR5) polypeptide or an isolated cell expressing a complement Factor H-related 5 (CFHR5) polypeptide in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 polypeptide comprises proline at a position corresponding to position 46 of SEQ ID NO:8; (d) a polynucleotide comprising a sequence encoding a CFHR5 polypeptide, said sequence operably linked to a promoter in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 polypeptide comprises proline at a position corresponding to position 46 of SEQ ID NO:8; (e) an agent that reduces expression of a CFH variant polypeptide associated with increased risk of developing membranoproliferative glomerulonephritis type II (MPGNII) in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFH variant polypeptide comprises histidine at a position corresponding to position 402 of SEQ ID NO:2; or (f) an agent that reduces expression of a CFHR5 variant polypeptide associated with increased risk of developing MPGNII in the preparation of a medicament for prevention or treatment of membranoproliferative glomerulonephritis type II (MPGNII), wherein the CFHR5 variant polypeptide comprises serine at a position corresponding to position 46 of SEQ ID NO:8.