Gender balance in patients with systemic lupus erythematosus.

Factors are reviewed that contribute to the contemporary view of a disproportionate prevalence and incidence of SLE in females. Recent studies on the epidemiology of SLE report that global incidences and prevalences of SLE for Caucasian and Black populations are of the order of 5.5 and 13.1 per year and 81 and 212 per 100,000 persons respectively. Both parameters displayed age dependent variation over a 90-year lifespan. The female to male (F:M) incidence of SLE varied with age, being approximately 1 during the first decade of life, followed by a sharp increase to 9 during the 4th decade, thence declining in subsequent decades before an increase during the 7th or 8th decade. A cognate review of SLE diagnosis in neonates revealed a F:M ratio of ≈1.2, consistent with the epidemiology review and the sporadic nature of SLE. Notional estimates of disease duration showed a steady increase from a base level for both males and females. The linear trend line for males was always lower than the trend line for females, supporting clinical experience that SLE is a more severe disease in males. Over a 14-year interval ending in 2012, the notional duration of SLE increased from 10-15years to 20-25years, probably reflecting advances in diagnosis and clinical practice. A metastudy of SLE concordance in twins revealed a 75% discordance in monozygotic twins compared to a 95% discordance in dizygotic twins confirming the importance of environmental factors in susceptibility to SLE. The elevated discordance in dizygotic SLE twins (and between siblings) suggests a role for the intrinsic genomic sexual dimorphism due to divergence of Y chromosome regulatory loci from their X chromosome homologues due to lack of recombination of mammalian sex chromosomes over evolutionary time. Estimates were made of the incidences of SLE in males and females based on population data for nine autosomal deficiency loci of major effect, plus expected male prevalence associated with Klinefelter's syndrome and female prevalence associated with Triple X syndrome. These genetic abnormalities accounted for ≈4% of female and ≈23% of male Caucasoid prevalence and for SLE resulting in a F:M ratio of ≈0.17. It may be deduced therefore that the impressive preponderance of SLE in females arises from a combination of environmental triggers and susceptibility loci of relatively small effect acting between the interval from the mini-puberty of childhood to the peak of reproductive adulthood. It is in this cohort of females, and especially in the Black population, that combinations of loci of minor effect acting together with environmental factors initiate defective apoptosis resulting in consequential autoimmune disease especially SLE. We postulate that because apoptosis is itself a very complex process, and defective apoptosis is an important contributor to SLE, there will be many combinations of susceptibility loci and environmental stimuli that can result in SLE (and other autoimmune disease(s)), of varying severity.

Establishment of gene copy number-specific normal ranges for serum C4 and its utility for interpretation in patients with chronically low serum C4 concentrations.

OBJECTIVE: To establish gene copy number (GCN)-specific normal ranges for serum C4 genes and to determine their utility with respect to the interpretation of chronically low serum C4 concentrations in patients with clinically quiescent systemic lupus erythematosus (SLE). METHODS: C4 serum concentrations were estimated by automated turbidimetry, and C4 GCNs were determined using the TaqMan real-time polymerase chain reaction (PCR) analysis in 184 unselected individuals and in 10 patients with type 1 diabetes mellitus (DM) who were selected for the presence of only 2 copies of the C4 gene. C4 GCNs were also determined in 11 patients with clinically quiescent SLE who had chronically low serum C4 concentrations. RESULTS: A total of 33% of the variation in serum C4 concentrations could be accounted for by both C4A and C4B GCNs (R(2) = 0.30, P ≤ 0.0001). There was a median of 2 gene copies at the C4A locus (53.8%) and 2 at the C4B locus (58.7%). The median total number of C4 genes was 4 (55.4%). C4 GCN-specific normal ranges were established. A chronically low serum C4 concentration was explained by a low C4 GCN in 3 of 11 patients tested. CONCLUSION: This study establishes the feasibility of establishing C4 GCN-specific normal ranges using the TaqMan real-time PCR assay. Chronically low serum C4 concentrations in SLE patients are sometimes explained by low C4 GCNs.

Characterization of the sheep Complement Factor B gene (CFB).

The Complement Factor B gene (CFB) of the alternative complement pathway has been identified in the sheep Major Histocompatibility Complex (MHC) and its genomic sequence determined. CFB is located approximately 600 bp upstream of the complement C2 gene, contains 18 exons, and manifests the domain signature characteristic of CFB protein. Thirteen single nucleotide polymorphisms were identified in merino sheep and interbreed variation was identified by comparison with International Sheep Genomics Consortium data. Two predicted non synonymous substitutions were observed and in-silico analysis indicates that these are likely to have a destabilizing effect on the protein structure. Sheep and cattle CFB were compared and shown to contain a common nine nucleotide deletion in exon 18 relative to human CFB. Predicted CFB amino acid sequences for these two species contain 761 aa relative to 764 aa in the human orthologue. Sequencing of the cosmid and BAC clones used in this study permitted the relative positions of three adjacent loci to be determined and showed that the previously described microsatellite locus (BfMs) is located within SKIV2L.