Eicosanoid production in rheumatoid synovitis

Leukotriene B₄ (LTB₄) synthesis in rheumatoid synovitis was studied using peripheral and synovial fluid polymorphonuclear leukocytes (PMNs) and rheumatic synovial lining cells. No differences were found in LTB₄ synthesis between peripheral PMNs from healthy volunteers and rheumatoid arthritis patients. When peripheral and synovial PMNs from the same RA patient were compared, arachidonic acidinduced LTB₄ synthesis in synovial fluid PMNs was increased 1.7–7.2 fold, whereas the response to Ca ionophore A23187 stimulation was similar. This suggests 5-lipoxygenase stimulating factor(s) in inflamed joints. Rheumatic synovial lining cells in a primary cell culture produced small amounts of LTB₄, the concentrations being less than 0.1 per cent of those of prostaglandin E₂ (PGE₂). PGE₂ synthesis in synovial cells was increased when arachidonic acid or interleukin-1 was added to the culture, whereas LTB₄ production remained unaltered. The present results suggest that in inflamed joints LTB₄ originates mainly from PMNs whereas synovial lining cells are the source for PGE₂.