The anaphylatoxin C5a is generated upon complement activation and contributes to the development of many inflammatory disorders, including glomerulonephritis (Welch, 2002), pulmonary hypersensitivity (Shushakova et al., 2002), and contact hypersensitivity (Tsuji et al., 2000). The gene discussed is C5AR1; the disease is glomerulonephritis.