Contrasting patterns of newer histocompatibility determinants in patients with rheumatoid arthritis and systemic lupus erythematosus.

The Ia alloantigens as measures of different alleles of loci in the major histocompatibility complex were determined in patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA). The Ia specificities of reagents used were defined by their pattern of reaction with lymphoblastoid lines derived from normal donors homozygous for HLA-D determinants. The reagent specificities included those associated with a single Dw type as well as those reacting with a single specificity shared by several Dw types. Patients with RA had a marked elevation in the frequency of alloantigens detected by reagent sera that recognize various determinants shared by cell lines from HLA-Dw4, Dw7, or Dw10 individuals (Ia 4-7-10). The frequency of mixed lymphocyte culture alleles Dw4 and Dw10 was found to be increased; however this elevation did not approach the higher frequency for the serologically determined antigens of the Ia 4-7-10 group. In contrast, patients with SLE had an increased frequency of reactions with the reagent alloantisera defined by reactions with either HLA-Dw2 or Dw3 positive cell lines. The data suggest that immunogenetic factors are relevant to both groups of patients, but that these are entirely distinct for each disease.