CHARACTERIZATION OF MURINE MONOCLONAL-ANTIBODIES AGAINST THE RO52 AUTOANTIGEN

Immunization of BALB/c mice with purified recombinant human Ro52 prote in resulted in three anti-Ro52 MoAbs termed 2E7, 4C6 and 4F11. All ant i-Ro52 MoAbs specifically reacted with recombinant human Ro52 protein, and also with Ro52 protein in total extracts of all human cell lines analysed, including the epithelial cell line HeLa, the B cell line Raj i, the bladder carcinoma cell line RT112, and a fibroblast cell line d erived from patients with xeroderma pigmentosum. The anti-Ro52 MoAbs w ere able to immunoprecipitate the recombinant human Ro52 protein expre ssed in wheat germ extract, but failed to precipitate hY RNAs from cel l extracts. The staining pattern of the MoAbs strongly differed betwee n the RT112 cells and the fibroblast cell line. RT112 cells displayed an intense cytoplasmic staining and in addition distinct fine nuclear speckles. In contrast, in the fibroblast cell line no cytoplasmic stai ning but only staining of distinct nuclear speckles was observed. Usin g deletion mutants of Ro52 the epitopes recognized by the anti-Ro52 Mo Abs 2E7, 4C6 and 4F11 were partially mapped. All three MoAbs appeared to recognize distinct epitopes, that are located in the regions of Ro5 2 bordered by amino acids 136-164, 208-363 and 136-190, respectively. These MoAbs can be of great use in studying the cellular processes in which the Ro52 protein is involved.