To test the effect of infusions of CAMPATH-1H on levels of proinflammatory secretory phospholipase A2 (sPLA2) and tumor necrosis factor alpha (TNF-alpha) in patients with rheumatoid arthritis (RA).
Two patients with RA were infused with CAMPATH-1H; extracellular nonpancreatic sPLA2 activity was tested using radiolabelled E. coli membrane phospholipid, and circulating TNF-alpha levels were tested by ultrasensitive immunoassay.
Circulating TNF-alpha began to rise within the first 2 h after infusion, reaching > 1000-fold values compared to preinfusion levels. Circulating sPLA2 activity began to rise a few hours after the start of infusion and reached extremely high values in 12 h, concomitant with fever and hypotension. The activity of sPLA2 decreased to pretreatment values in 3-18 days after infusion.
The mechanism leading to the increase of TNF-alpha and hyperphospholipasemia A2 has not been elucidated. It is possible that CAMPATH-1H activates cells that synthesize and release TNF-alpha and sPLA2, and/or that it induces interleukin 2 release, which in turn activates TNF-alpha, with subsequent release of sPLA2.