Monoclonal anti-idiotypic antibodies against monoclonal rheumatoid factors derived from patients with Sjögren's syndrome.

Monoclonal anti-idiotypic antibodies (mA-IDs) were produced against IgM-K, IgA-L and IgA-K monoclonal rheumatoid factors (mRFs), respectively, derived from patients with Sjögren's syndrome (SS). Each mA-ID inhibited the RF activity of the autologous M-protein, but did not inhibit the activity of the other mRFs. As for the specificity of mA-IDs, it was confirmed to bind only to the mRF used for immunization. A cross-reactive idiotype (CRI) was detected in 3 out of 106 polyclonal RFs (pRFs) using AW5/3 mA-ID by double immunodiffusion or ELISA inhibition assay on pRF activity. However, no CRI was detected on AMB1/5 or SF18/2 mA-ID. One of the mA-IDs, AW5/3, cross-reacted with nuclei of proliferating lymphocytes, such as PHA-stimulated lymphocytes, interleukin 2 dependent T cell lines, B-lymphoblastoid cell lines or cultured lymphoma cell lines, but barely reacted with nuclei of normal resting lymphocytes.