Depressed degranulation response of synovial fluid polymorphonuclear leucocytes from patients with rheumatoid arthritis to IgG aggregates.

No difference was found between the degranulation responses to FMLP of synovial fluid (SF) polymorphonuclear leucocytes (PMNL), from patients with rheumatoid arthritis (RA), and either paired blood PMNL or blood PMNL from a healthy donor. In contrast, the response of SF PMNL to heat-aggregated IgG was often reduced compared with autologous blood PMNL. Similarly, SF from some (35%) RA patients stimulated degranulation of PMNL but the response of SF-derived PMNL to autologous stimulatory SF was reduced compared with the response of blood PMNL. The stimulatory activity of the SF was removed by sepharose-protein A. These results were taken to suggest that the activity is due to immunoglobulin aggregates and that SF PMNL (from some RA patients) are tachyphylactic to stimulation by immunoglobulin aggregates as measured by degranulation because they have been stimulated by immunoglobulin aggregates in vivo. In other studies the concentration of myeloperoxidase (MPO) was measured enzymically in RA SF and was found to be present in varying amounts. However, only a weak relationship was found between MPO levels and either PMNL numbers or levels of complement-bearing IgG aggregates in SF. It is considered that the relationship between MPO and immunoglobulin aggregates levels is obscured by the presence of a peroxidase inhibitor in the fluids and/or because only aggregates bound to tissue stimulate degranulation in vivo.