Heterologous specificity of reticulin RS antibodies.

: Reticulin antibodies were detected by the indirect immunofluorescence technique in 1450 sera from miscellaneous patients. R1 pattern on human and rat tissues was found only in 2 cases with adult coeliac disease. Reticulin Rs staining, involving intrasinusoidal cells of rat liver as well as interstitial and endothelial structures of various rat tissues, was demonstrated in 3.7% of cases, without correlation with gastro-intestinal or skin disorders. Rs pattern, due to IgG antibodies, could be absorbed by rat erythrocytes. Only Rs positive sera showed high titres of anti-rat IgG-type hemoagglutinins. Rat RBC agglutinating activity was demonstrated by a modified indirect Coomb's test. Heterologous Rs antibodies appear unrelated to particular diseases and should not be mistaken for the R1 and R2 patterns, which may be useful for diagnostic procedures.