http://www.nlm.nih.gov/medlineplus/ency/article/003354.htm NIH document says http://www.nlm.nih.gov/medlineplus/ency/article/003354.htm Complement Component 4 http://www.nlm.nih.gov/medlineplus/ency/article/003354.htm http://www.nlm.nih.gov/medlineplus/ency/article/003354.htm Medline Plus: Componente 4 do complemento (C4) [em inglês] NIH document says C4 level