ORGAN DISTRIBUTION OF THE RO (SS-A) ANTIGEN IN THE GUINEA-PIG

Using an anti-Ro (SS-A)-specific "sandwich" enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting, we determined the Ro (SS-A) content (both quantitative and qualitative) in saline-perfused organs of the guinea pig. All tissue extracts contained substantial concentrations of Ro (SS-A) antigen and could be grouped into 3 categories based on quantitative reactivity in the sandwich ELISA. The 60-kd and 52-kd molecular forms of Ro (SS-A) present in tissue extracts were similar to those described in Wi-L2 extracts, and the 54-kd molecular form of Ro (SS-A) in guinea pig erythrocytes was similar to that found in human erythrocytes. The tissue distribution of the isoforms of Ro (SS-A) was shown by Western immunoblotting to vary in different tissues, and the reactivity to the 60-kd Ro (SS-A) was correlated with the activity seen in the ELISA. Both the 60-kd and 53-kd Ro (SS-A) bands in guinea pig liver extracts were very weak on Western immunoblots, in contrast to the high concentration of Ro (SS-A) antigen in the ELISA. Other data suggest the possible existence of a unique form of Ro (SS-A) in the liver. Guinea pig tissues have 4 Y RNA that are equivalent to the 4 human RNA-hY1, hY3, hY4, and hY5-present in HeLa cells, while guinea pig red blood cells have only one Y RNA, which is equivalent in size to human hY4. This heterogeneity of the Ro (SS-A) antigen suggests that there is differential expression of the various Ro (SS-A) genes in different tissues and expands the possibilities for tissue-specific pathologic events involving the Ro (SS-A)/anti-Ro (SS-A) system.