Antibodies to Ro(SSA) and the heterogeneity of systemic lupus erythematosus.

The clinical heterogeneity of systemic lupus erythematosus (SLE) is associated with a multiplicity of autoimmune responses to both cellular and soluble antigens. At least part of the clinical heterogeneity is associated with serological heterogeneity and this is particularly striking among patients with SLE who produce anti-Ro(SSA) and anti-La(SSB). Certain subsets within the lupus spectrum are closely associated with the anti-Ro(SSA) response. These include subacute cutaneous lupus erythematosus, the lupus like syndrome associated with homozygous C2 and C4 deficiency, and neonatal lupus erythematosus. Moreover, among the patients with SLE who produce anti-Ro(SSA) are 2 stable groups, on which produces anti-Ro(SSA) alone and one which produces both anti-Ro(SSA) and anti-La(SSB). Clear clinical and serological differences distinguish these groups and it is hypothesized that these differences are due to genetic differences in the HLA-D region. Exact identification of the genes involved and how they control immune responses should lead to a clearer understanding of the clinical phenomena seen in these patients.