Objective. To analyze the presence and specificity of anti-alpha-enolase an
tibodies in various systemic autoimmune diseases.
Methods. Sera from patients with systemic lupus erythematosus (SLE), mixed
cryoglobulinemia (MC), systemic sclerosis (SSc), and rheumatoid arthritis (
RA) were tested by immunoblot on partially purified alpha-enolase from huma
n kidney and on beta- and gamma-enolase. The isotype of anti-enolase antibo
dies was determined by means of isotype-specific monoclonal antibodies.
Results. IgG anti-alpha-enolase antibodies were detected in 9/33 (27%) SLE
sera (6/9 patients had active renal disease), in 6/19 sera from patients wi
th MC and nephritis, in 0/15 sera from MC patients without renal involvemen
t, in 6/20 (30%) SSc sera, in 2/35 (67%) disease controls with RA, and in 2
/32 (6%) healthy controls. The antibodies were not species-specific, but in
most cases were specific for the alpha isoform of enolase. The anti-enolas
e immune response was not isotypically restricted. In half of the patients
with SLE the anti-alpha-enolase and anti-DNA antibodies constituted distinc
t antibody populations, while in the other half a partial overlap of the 2
antibody specificities was observed.
Conclusion. Anti-alpha-enolase antibodies can frequently be detected in sys
temic autoimmune disorders. In SLE and MC they are associated with nephriti
s and in SSc they are associated with severe endothelial damage. Alpha-enol
ase is ubiquitous, but is highly expressed in the kidney and also on the me
mbrane of several cell types including endothelial cells. Thus, anti-alpha-
enolase antibodies could contribute to renal injury not only by the local f
ormation of immune complexes, but also by direct damage to endothelial cell
s.