AB0702 IGG and IGM anti-DSDNA isotypes in patients with systemic lupus erythematosus

Background Systemic lupus erythematosus (SLE) is an autoimmune disease, where renal involvement is common, being a determinant for bad prognostic. Lupus nephritis is generally associated to the presence of anti-dsDNA. The IgM isotype of this autoantibody, unlike the IgG isotype, seems to be nephroprotector. Objectives To study the influence of isotypes IgG and IgM anti-dsDNA antibodies on clinical and laboratory manifestations of SLE. Methods We conducted a cross-sectional study with 137 patients with SLE, in which we explored the presence of isotypes IgG and IgM anti-dsDNA antibodies. The research of anti-dsDNA was performed by indirect immunofluorescence with Crithidia luciliae (CLIF). Results Fifty-eight (42%) patients had IgG anti-dsDNA reagent and were selected for the study of the IgM isotype. The group of patients who had anti-dsDNA IgG alone (n=43) compared with the group who had concomitant isotypes IgG and IgM (n=15), showed a higher frequency of active urine sediment (34.9% versus 6.7%, p=0.046). Analysis of the median distribution of IgG/IgM anti-dsDNA ratio, according to the presence or absence of clinical and laboratory features, showed a trend of the IgG/IgM ratio be greater in the presence of arthritis and leukopenia/lymphopenia [4 (2-8)versus 1 (1-2), p=0.070 and 4 (3-8) versus 1 (1-4), p=0.066, respectively]. Conclusions Our study showed that the concomitance of the isotypes IgM and IgG anti-dsDNA inhibited the effect of the isotype IgG isolated in association with active urinary sediment. Future studies are needed to clarify the role of anti-dsDNA isotypes in SLE. References Bootsma, H., et al., The predictive value of fluctuations in IgM and IgG class anti-dsDNA antibodies for relapses in systemic lupus erythematosus. A prospective long-term observation. Ann Rheum Dis, 1997. 56(11):661-6. Witte, T., et al., IgM anti-dsDNA antibodies in systemic lupus erythematosus: negative association with nephritis. SLE Study Group. Rheumatol Int, 1998. 18(3):85-91. Forger, F., et al., Clinical significance of anti-dsDNA antibody isotypes: IgG/IgM ratio of anti-dsDNA antibodies as a prognostic marker for lupus nephritis. Lupus, 2004. 13(1):36-44. Munoz, L.E., et al. Predictive value of anti-dsDNA autoantibodies: importance of the assay. Autoimmun Rev, 2008. 7(8):594-7. Atta, A.M., et al., Anti-dsDNA antibodies in Brazilian patients of mainly African descent with systemic lupus erythematosus: lack of association with lupus nephritis. Clin Rheumatol, 2009. 28(6):693-7. Disclosure of Interest None Declared