Complement-fixing granulocyte-specific antinuclear factors in neutropenic cases of rheumatoid arthritis.

Forty-one sera from patients with rheumatoid arthritis (RA) and accompanying neutropenia, including twenty-one with Felty's syndrome, were studied to investigate the occurrence and determine the titres of granulocyte-specific antinuclear factors (GS-ANF) belonging to the three main immunoglobulin classes. Furthermore complement (C3) fixing GS-ANF and rheumatoid factors were titrated in the sera. Complement-fixing GS-ANF were found in thirty-five of these sera compared with only four out of twenty-eight sera from RA patients without neutropenia. Complement-fixing GS-ANF were similarly detected in all of six sera from non-arthritic patients with severe neutropenia and positive Waaler—Rose tests. Complement-fixing properties of the antibodies were mostly found in sera containing high titres of GS-ANF of the IgG and IgM classes, but the titres of complement-fixing GS-ANF were on the whole markedly lower than the corresponding IgG and IgM antibody titres. A direct autoaggressive activity of complement-fixing GS-ANF on the neutrophilic granulocytes or their precursors is suggested.