Systemic lupus erythematosus is not associated with allotypic markers of immunoglobulin kappa in Caucasians.

OBJECTIVE

To determine whether systemic lupus erythematosus (SLE) is associated with a specific Km genotype or allele. Specific genetic markers located both within the major histocompatibility complex (MHC) and outside the MHC have been associated with SLE. However, serologic studies of Km allotypes have led to contradictory results.

METHODS

A novel molecular genetic technique was used to determine Km genotypes. First, the kappa constant segment (C kappa) was amplified from genomic DNA by the polymerase chain reaction (PCR). Then the resulting PCR product was subjected to restriction enzyme digestion. AccI cleavage of the C kappa PCR product correlated with Km (3) allotype, and presence or absence of an MaeII site correlated with Km (1) or Km (1, 2), respectively.

RESULTS

There was no difference in the distribution of Km genotypes or alleles between Caucasian patients with SLE (n = 26) and controls (n = 107). Clinical features did not differ in 4 Km (1, 2) positive patients with SLE compared to 22 Km (1, 2) negative patients with SLE, nor did the frequency of anti-Sm or antinative DNA autoantibodies (2 Km (1, 2/3) versus 4 Km (3/3); and 1 versus 6, respectively). No Km (1, 2/3) positive individual had anti-La (anti-SSB) autoantibodies.

CONCLUSION

Genotypic frequencies of C kappa coding region markers (Km allotypes) do not differ between Caucasian patients with SLE and controls.