title: Is decreased blood plasma concentration of the complement C4B protein associated with attention-deficit hyperactivity disorder?
abstract: OBJECTIVE
  The complement system is a group of blood proteins that play an important role in defending against viral and bacterial infections. The objective of this investigation was to study the plasma levels of the C4B protein in attention-deficit hyperactivity disorder (ADHD) in an attempt to associate infections with the development of some cases of this disorder.
  
  
  METHODS
  C4B plasma protein levels were studied using an enzyme-linked immunosorbent assay in a group of 23 subjects meeting DSM-III-R criteria for ADHD and a similar number of age- and sex-matched controls. Also studied were parents of the ADHD subjects.
  
  
  RESULTS
  C4B plasma levels (157.0 micrograms/mL) in the ADHD subjects were significantly (p < .01) lower than those (239.3 micrograms/mL) in the normal age-matched subjects. Mothers of the ADHD subjects also had significantly lower C4B values compared with mothers of normal children. On the other hand, C4B values in the fathers were not significantly altered.
  
  
  CONCLUSIONS
  Decreased C4B levels in ADHD, if replicated, may represent an important marker for ADHD (or a subgroup of ADHD). It also seems plausible that C4B levels are an important etiological factor for ADHD.
authors.affiliation: Center for Persons with Disabilities, Utah State University, Logan 84322, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Warren
authors.forename: J D
authors.initials: JD
authors.lastname: Odell
authors.forename: W L
authors.initials: WL
authors.lastname: Warren
authors.forename: R A
authors.initials: RA
authors.lastname: Burger
authors.forename: A
authors.initials: A
authors.lastname: Maciulis
authors.forename: A R
authors.initials: AR
authors.lastname: Torres
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000097:blood* / Q000235:genetics / Q000821:virology; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015935:Complement C4b / Q000172:deficiency*; D005260:Female; D006801:Humans; D008285:Major Histocompatibility Complex; D008297:Male; D016555:Matched-Pair Analysis; D014777:Virus Diseases / Q000150:complications
chemical_list: D015415:Biomarkers; D015935:Complement C4b