Inheritance of monoclonal rheumatoid factor cross-reactive idiotypes in primary Sjogren''s syndrome (pSS). Comparative studies of a rabbit polyclonal anti-idiotype and 17109 monoclonal anti-idiotype

Abstract. A comparison of the presence of two idiotypes, one identified by a rabbit polyclonal anti-idiotypic antibody, first found on a cryoprecipitable IgM.± rheumatoid factor (RF) from an SS patient (3rd SS) and the 17109 idiotype, identified by a monoclonal antibody was performed in 106 sera and eight minor salivary gland biopsies of Sjögren's syndrome (SS) patients and 125 sera from age-sex matched normal controls. Of 106 of SS patients' sera 36 had immuno-globulins positive for the 3rd SS idiotype. 17109 activity was more prevalent in SS patients positive for the polyclonal anti-idiotype 3rd SS, than those with negative idiotype (9/36 VS 2/70 times2= 12.53 P <0.005). Cross inhibition studies, however, revealed that the polyclonal anti-idiotype binding was not inhibited by the 17109 moAb. 3rd SS and 17109 anti-idiotypes were reacted with immunoglobulins in the serum of 3–5% and 1.7% of normal human sera respectively. Immu-nohistologic studies demonstrated that 4/8 and 2/6 minor salivary gland biopsies had infiltrating plasma cells containing immunoglobulins bearing the 3rd SS and the 17109 idiotypes, respectively. The inheritance of both idiotypes was investigated in sera of 4 SS kindreds. In two kindreds with 3rd SS positive pro-bands, the idiotype was detected in 3 first degree relatives of the same generation. 17109 activity was detected in the serum of a sister of the positive proband who had a high RF titer. These results suggest that the 17109 moAb recognizes a different epitope of that of the 3rd SS. The idiotypes of monoclonal RFs are not inherited and probably are produced by plasma cells infiltrating the labial minor salivary glands of SS patients.