Changes in plasma fibronectin during donor apheresis and therapeutic plasma exchange

Changes in plasma levels of the opsonic glycoprotein fibronectin were studied during machine apheresis in 32 healthy plasma donors and 18 patients undergoing a total of 86 therapeutic plasma exchanges. Donation of 500 ml of plasma at 3-monthly intervals produced a 10% immediate decrease in plasma fibronectin with no evidence of a long-term affect on levels of this protein. One plasma volume exchange with fibronectin-poor plasma protein fraction produced subnormal plasma fibronectin levels in 98% of post-exchange samples. Efficiency of exchange was significantly lower in patients with paraproteinaemia, probably reflecting increased plasma volume in such patients. Daily plasma exchange produced progressive depletion of plasma fibronectin (index of recovery 0.68) whereas levels were maintained close to the initial value with longer exchange intervals, except in the more severely ill patients. Reduction of plasma fibronectin by plasma exchange may increase susceptibility to infection and reduce the efficacy of this procedure when the object of exchange is to reverse reticuloendothelial blockade.