Stimulation of human rheumatoid synovial cells by non-lethal complement membrane attack.

Area of Science:

• Immunology
• Rheumatology
• Cell Biology

Background:

• Rheumatoid arthritis involves chronic inflammation of synovial cells.
• The complement system plays a role in inflammatory processes.
• Understanding cellular responses to complement attack is crucial for rheumatoid arthritis research.

Purpose of the Study:

• To investigate the effects of non-lethal complement membrane attack on human rheumatoid synovial cells.
• To identify the specific complement complexes involved in cellular responses.
• To elucidate the downstream signaling pathways triggered by complement activation.

Main Methods:

• Cultured human rheumatoid synovial cells were subjected to non-lethal complement attack.
• Measurements included reactive oxygen metabolite release, prostaglandin E2 levels, leukotriene B4, and tumor necrosis factor.
• Specific complement complexes (C5b-9, C5b-8) and extracellular calcium were manipulated.

Main Results:

• Non-lethal complement attack induced rapid reactive oxygen metabolite release dependent on C5b-9.
• A biphasic release of prostaglandin E2 was observed, with the second phase dependent on C5b-8 and protein synthesis.
• Extracellular calcium removal reduced prostaglandin E2 release; leukotriene B4 was released in small amounts, but tumor necrosis factor was not detected.

Conclusions:

• Non-lethal complement attack significantly impacts rheumatoid synovial cells, inducing inflammatory mediator release.
• The findings highlight the differential roles of complement complexes in cellular responses.
• These cellular responses may contribute to the pathogenesis of rheumatoid arthritis, suggesting potential therapeutic targets.