Brief Definitive Report DETERMINANTS RECOGNIZED BY MURINE RHEUMATOID FACTORS: MOLECULAR LOCALIZATION USING A PANEL OF MOUSE MYELOMA VARIANT IMMUNOGLOBULINS* BY VI~RONIQUE STASSIN,* PIERRE G. COULIE,* BARBARA K. BIRSHTEIN, § DAVID S. SECHER, ! AND JACQUES VAN SNICK* *From the Unit of Experimental Medicine, Universit~Catholique de Louvain and International Institute of Cellular and Molecular Pathology, Brussels, Belgium; ~Departmentof Cell Biology, Albert Einsteb~ College of Medicine, Bronx, New York 10461; mMRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH, England It is now well established that rheumatoid factor (RF)-like anti-IgG autoanti- bodies frequently occur in the mouse (1-6). The development of RF-secreting hybridomas derived from polyclonally acti- vated spleen cells or obtained from animals spontaneously producing RF made it possible to study the fine specificity of these autoantibodies. It appeared that, whatever their origin, the majority of mouse monoclonal RF were specific for a single IgG subclass: most were directed against IgG1 or IgG2a, some against IgG2b. Competition experiments with heat-aggregated immunoglobulins showed that subclass specificity was also characteristic of the polyclonal RF found in the serum of autoimmune strains, NZB and MRL/MpJ-lpr (7). In addition, many IgG2a-specific RF derived from BALB/c (Igh a) or 129/Sv (Igh a) mice also displayed aliotype specificity in the sense that they failed to react with IgG2a of the "b" allotype. To localize the determinants involved in these RF-IgG interactions, we have investigated the reactivity of RF, both polyclonal and monoclonal with immu- noglobulins carrying abnormal heavy chains (8, 9). The results indicate that both the allotypic and isotypic determinants recog- nized by mouse RF are located in the C-terminal region of 3'1, 3"2a, and 3"2b heavy chains. Materials and Methods Rheumatoid Factors. RF-secreting hybridomas were derived from spleen cells of 129/ Sv, BALB/c, CBA/Ht, or C57B1/6 mice as described (5, 7). Both cell culture supernatants and purified proteins were used as a source of monoclonal RF. RF-containing sera were obtained from 20-wk old 129/Sv, MRL/MpJ-Ipr and NZB/BinJ mice. The former were maintained in our colony; the latter two were obtained from The Jackson Laboratory (Bar Harbor, ME). Protein,s. Hen egg white lysozyme was purchased from Koch-Light Laboratories Ltd * Supported by grants from F.N.R.S., F.R.S.M., and Loterie Nationale, Belgium. V. S. Is the recipient of a fellowshipfrom 1.R.S.I.A., Belgium. P. G. C. is the recipient of a fellowshipfrom the F.D.S., Universit~Catholique de Louvain (U.C.L.), Belgium. J. V. S. is a research associatewith the F.N.R.S., Belgium. J. ExP. MEn. © The Rockefeller University Press • 0022-1007/83/11/1763/06 $1.00 1763 Volume 158 November 1983 1763-1768 Downloaded from http://rupress.org/jem/article-pdf/158/5/1763/1664420/1763.pdf by guest on 20 May 2024