Anti-NuMA antibodies: an uncommon specificity in scleroderma sera.

Background: Serum antibodies in scleroderma patients are generally directed against the nucleolus and centromeres. A small proportion of patients have serum antibodies to the centrioles and mitotic apparatus.

Objective: To determine the prevalence of serum autoantibodies against the mitotic apparatus in scleroderma patients.

Material and methods: Sera from 113 patients with various forms of scleroderma were tested for antinuclear antibodies by indirect immunofluorescence on HEp-2 cells. The specificity of the antibodies was determined by Western blot.

Results: Only two scleroderma sera recognized the mitotic apparatus. Western blot results showed that in both cases the target was an about 235 kDa protein corresponding to the NuMA determinant. Affinity-purified anti-NuMa antibodies were used to perform immunolocalization in synchronized HEp-2 cells using scanning laser confocal microscopy. The anti-NuMA autoantibodies recognized the mitotic asters but neither the centrioles nor the microtubules.

Conclusion: Our data suggest that anti-NuMA autoantibodies may be devoid of clinical significance in scleroderma. However, they remain useful as probes in cell biology studies.