Detection of IgG rheumatoid factor secreting cells in autoimmune MRL/1 mice: a kinetic study

The kinetics of appearance of cells secreting IgG rheumatoid factor (IgG RF) has been studied in MRL/l mice by means of the ELISPOT assay, a new immunoenzyme procedure. Mice of the MRL/l strain spontaneously develop an autoimmune disease associated with arthritic manifestations. IgG RF secreting splenocytes were first detected at the clinical onset of the disease at the age of 3 months. Peak frequencies of IgG RF secreting cells amounting to almost 10% of the total number of IgG secreting cells were observed at later stages. The appearance of IgG RF secreting cells was preceded by at least 1 month by elevated levels of circulating immune complexes and abnormally high numbers of IgG secreting cells. The frequencies of IgG RF secreting cells and of IgG secreting splenocytes did not follow each other at least not during the first 3 months preceding the onset of clinical disease. The data presented suggest that IgG RF production in MRL/l mice is not triggered as part of an early stage of polyclonal activation but could be induced by IgG containing immune complexes.