ANTIPERINUCLEAR FACTOR OF THE IGA ISOTYPE IN ACTIVE RHEUMATOID-ARTHRITIS

Objective: For rheumatoid arthritis (RA), antiperinuclear factor (APF) is as efficient a marker as rheumatoid factor (RF). However, the prev alence and significance of APF of the IgA isotype in active RA, as wel l as its correlation with RF-IgA, have not been determined. Our goal w as to obtain information on these points. Methods: APF-IgA were screen ed in 80 sera from patients with active RA, prospectively and consecut ively selected over an 8-month period. Sera from 22 patients with Sjog ren's syndrome and 50 with lupus were also studied retrospectively for APF-IgG and IgA. Results: APF-IgA were found at a 1:10 dilution or ab ove in 31 RA sera (39%), which were all positive for APF-IgG as well a t higher titers. In the 64 sera positive for APF no correlations were found between APF-IgA and IgA or immune complexes-IgA, latex, the Rose -Waaler test and RF-IgA. Conversely, an association of APF-IgA was fou nd with both APF-IgG (p<0.0001) and anti-stratum corneum of rat esopha gus (ASC)-IgG (p<0.0001). APF-IgA, though correlated with the presence of secondary sicca syndrome in RA (p=0.0023), was not more frequent ( 5/22) in primary Sjogren's sera. Conclusions: RF-IgA and APF-IgA are n ot correlated Despite its localization in the mucosae, the target anti gen for APF elicit fewer IgA antibodies in RA than does the RF target.