Nephritic factor (NeF) of alternate pathway (NeFA) and of classical pathway (NeFc).

NeFA and NeFc were studied in various cases (115 cases). 5 cases were followed up for a long time. NeFA assay was done by the "microtest plate method". We detected the NeF activity for the first time in the cases of Sjögren syndrome (SjS) and SjS+SLE+Hashimoto's disease (Hashimoto). In some cases NeF activity disappeared after therapy, and in one case NeFA and NeFc were positive at first, but then only NeFA activity became negative following the adequate therapy. As to the antibody nature of NeF, the possibility was suggested that NeFA might be anti C3b autoantibody and NeFc might be anti C4b and/or C4b2a auto-antibody.