title: [The relation between the HLA-DRB1*1501 allele and the severity of multiple sclerosis in a sample of the Spanish population from the Balearic Islands: the influence exerted by sex].
abstract: BACKGROUND
  There is some controversy about the possible relation between HLA-DR2 (DRB1*1501-DRB5*0101-DQA1*0102-DQB1*0602) and the severity of multiple sclerosis (MS), which could be due, at least in part, to methodological differences among the different studies dealing with this subject and/or to a lack of phenotypic homogeneity within the series of patients.
  
  
  OBJECTIVE
  This study aims to contribute information about the possible relation between DR2 (more specifically the HLA-DRB1*1501 allele) and the severity of MS.
  
  
  METHODS
  We conducted a study of 43 individuals with clinically defined MS, whose degree of severity was determined using Kurtzke's EDSS, and 107 controls from a similar ethnic origin. DETERMINATIONS: HLA typing by PCR-SSO and PCR-SSP, analysis of oligoclonal IgG bands in CSF by isoelectric focusing, and quantification of the intrathecal synthesis of IgG (IgG index, IgG ratio, Reiber's formula and Tourtellotte's formula).
  
  
  METHODS
  Chi2 test, Mann-Whitney test and Kendall correlation coefficient.
  
  
  RESULTS
  DRB1*1501 is associated with the presence of MS only in females and with lower severity of the disease only in males. These associations do not appear to depend on any kind of effect exerted by DRB1*1501 on the intrathecal synthesis of IgG that differs between the two sexes.
  
  
  CONCLUSIONS
  The absence of a relation between DRB1*1501 and the severity of MS reported in many studies could be due to not stratifying the patients according to sex. Our findings emphasise how important it is in genetic studies of complex traits to reduce the phenotypic heterogeneity of patients as much as possible.
authors.affiliation: Fundación Balear Transplant, Palma de Mallorca, España.
authors.forename: J M
authors.initials: JM
authors.lastname: Zabay-Becerril
authors.forename: J
authors.initials: J
authors.lastname: Burcet-Dardé
authors.forename: J
authors.initials: J
authors.lastname: Mulet-Ferrer
authors.forename: J
authors.initials: J
authors.lastname: Soler-Farré
authors.forename: C
authors.initials: C
authors.lastname: Viader-Farré
mesh_terms: D000293:Adolescent; D000328:Adult; D000483:Alleles; D005260:Female; D006684:HLA-DR Antigens / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006801:Humans; D008297:Male; D009103:Multiple Sclerosis / Q000235:genetics*; D012720:Severity of Illness Index; D012737:Sex Factors; D013030:Spain
chemical_list: D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains