HYPOTENSIVE ACTION OF AGGREGATED IGG IN RATS - STUDY OF THE UNRESPONSIVENESS TO A 2ND DOSE FOLLOWING RESTORATION OF THE BLOOD-PRESSURE

Human IgG preparations containing aggregates have been reported to ind uce hypotension in rats. Animals surviving a hypotensive dose of such a preparation were found unresponsive to a second dose given the next day. Unresponsiveness was induced by an isolated fraction of aggregate d IgG, but not by purified monomers. Preparations containing aggregate d and monomeric IgG appeared more efficient in inducing unresponsivene ss than aggregates alone. The phagocyte function in vivo was assessed in unresponsive animals. No significant difference was found in the ca rbon clearance and in the human erythrocyte clearance test suggesting that a general impairment of the phagocyte function is not necessary f or unresponsiveness. Previous studies indicated the involvement of PAF in hypotension by aggregated IgG. Hypotension was elicited by the inj ection of PAF in rats made ''refractory'' to aggregated IgG like in co ntrols.