title: Deficiency of human complement factor I associated with lowered factor H.
abstract: Deficiencies of factor I and/or factor H result in an increased consumption of C3 and higher susceptibility to recurrent infections. Here we describe a case of human factor I deficiency and lowered factor H levels. C3 concentration was 50% lower than normal, the classical pathway-dependent hemolytic activity was reduced to almost 30% of normal, and alternative pathway-dependent activity was completely absent. The killing by peripheral leukocytes of Candida albicans treated with deficient serum and the production of complement-dependent chemotactic factors were reduced in the proband's serum when compared with normal serum. Finally, we observed that C3 antigen present in the proband's serum has a different electrophoretic mobility than native C3 (most likely C3b), confirming the deregulation of complement activation due to the lack of regulatory proteins factors I and H. The impaired complement system described in this case, the first of its kind described in a Chile, explains the higher susceptibility to infections found in the proband.
authors.affiliation: Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, 05508-900, Brazil.
authors.forename: G M
authors.initials: GM
authors.lastname: Naked
authors.forename: M P
authors.initials: MP
authors.lastname: Florido
authors.forename: P
authors.initials: P
authors.lastname: Ferreira de Paula
authors.forename: A M
authors.initials: AM
authors.lastname: Vinet
authors.forename: J S
authors.initials: JS
authors.lastname: Inostroza
authors.forename: L
authors.initials: L
authors.lastname: Isaac
mesh_terms: D000818:Animals; D002630:Chemotactic Factors / Q000096:biosynthesis; D002633:Chemotaxis; D002648:Child; D002675:Child, Preschool; D003176:Complement C3 / Q000032:analysis; D003179:Complement C3b; D017242:Complement Factor H / Q000378:metabolism*; D017244:Complement Factor I / Q000172:deficiency*; D003170:Complement Pathway, Alternative / Q000502:physiology; D003171:Complement Pathway, Classical / Q000502:physiology; D004912:Erythrocytes; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007122:Immunoelectrophoresis; D008297:Male
chemical_list: C493495:CFH protein, human; D002630:Chemotactic Factors; D003176:Complement C3; D003179:Complement C3b; D017242:Complement Factor H; D017244:Complement Factor I