title: C4A deficiency in children and adolescents with recurrent respiratory infections.
abstract: Increased susceptibility to recurrent viral and bacterial respiratory infections in children and young adults is not well understood. To evaluate the role of complement factor C4 in the defense against respiratory infections, we studied complement factor C4 allotypes C4A and C4B and copy numbers of C4A and C4B genes in 84 children and young adults with recurrent acute otitis media, sinusitis, or pneumonia and in 74 healthy controls. The occurrence of C4A gene deficiency was significantly higher in patients compared with controls (26% vs 14%, p = 0.048). Girls predominated in the group of patients with C4A deficiency (73% girls and 27% boys, p = 0.004). The lectin pathway of complement was more often functionally impaired in patients with C4A deficiency than in patients with no C4A deficiency (41% vs 13%, p = 0.033). Classical and alternative pathways were normal in individuals with C4 null alleles. C4A deficiency is 1 of the minor defects of the innate immunity that may predispose children and young adults to recurrent respiratory infections. C4 gene testing should be added to the list of investigations when the cause for recurrent acute otitis media, maxillary sinusitis, or pneumonia in children and young adults is sought.
authors.affiliation: Department of Pediatrics, Turku University Hospital, Turku, Finland. leena.kainulainen@tyks.fi
authors.forename: Leena
authors.initials: L
authors.lastname: Kainulainen
authors.forename: Ville
authors.initials: V
authors.lastname: Peltola
authors.forename: Mikko
authors.initials: M
authors.lastname: Seppänen
authors.forename: Markku
authors.initials: M
authors.lastname: Viander
authors.forename: Qiushui
authors.initials: Q
authors.lastname: He
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Lokki
authors.forename: Olli
authors.initials: O
authors.lastname: Ruuskanen
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015934:Complement C4a / Q000172:deficiency / Q000235:genetics / Q000276:immunology*; D015935:Complement C4b / Q000235:genetics / Q000276:immunology; D037582:Complement Pathway, Mannose-Binding Lectin / Q000276:immunology; D005260:Female; D018628:Gene Dosage / Q000276:immunology; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics*; D007223:Infant; D008297:Male; D010033:Otitis Media / Q000235:genetics* / Q000276:immunology; D011014:Pneumonia / Q000235:genetics* / Q000276:immunology; D012008:Recurrence; D012737:Sex Factors; D012852:Sinusitis / Q000235:genetics* / Q000276:immunology
chemical_list: D015934:Complement C4a; D015935:Complement C4b