Electroimmunoassay of alpha-2-opsonic protein during reticuloendothelial blockade

Physiological regulation of reticuloendothelial (RE) phagocytic activity by a plasma opsonic factor has been documented. In the recent study, serum levels of this alpha-2-opsonic protein in rats during colloid-induced RE blockade were measured utilizing an electroimmunoassay (Rocket immunoelectrophoresis) with monospecific antiserum to the purified alpha-2-glycoprotein. RE blockade was produced by the intravenous injection of the gelatinized "RE-test-lipid emulsion" at a dose of 50 mg/100 g body wt. The opsonic activity of serum at various intervals during colloid-induced RE blockade as measured by tissue slice bioassay manifested a high correlation (r = 0.98) with the serum opsonic protein concentration as measured by the electroimmunoassay. During RE blockade (30 min), there was a rapid depletion of the opsonic alpha-2-glycoprotein to 20% of the initial preinjection levels. Serum concentration of this glycoprotein remained low for at least 2-3 h after which time its concentration progressively increased with approximation of normal values by 6 h postblockade. Opsonic protein concentration at 24 h postinjection were significantly (P less than 0.05) elevated above controls. Thus, colloid-induced RE blockade is associated with the removal of this glycoprotein from the serum and recovery from RE blockade is accompanied by a restoration of opsonin levels. The electroimmunoassay can provide a sensitive technique to monitor this humoral factor known to exert a physiological control on the RE system.