Blockade of the RES was accomplished by the intravenous injection of carbon particles, thorotrast, zymosan, or a suspension of Bordetella pertussis. The blockade resulted in a decrease in sensitivity to anaphylaxis produced by the intravenous injection of soluble antigen-antibody complexes consisting of an optimal shocking mixture of bovine plasma albumin and mouse antibody to this antigen. The decrease in sensitivity to anaphylaxis was dependent on the dose of blockading agent and on the time between blockade and challenge with complex. The loss of sensitivity to anaphylaxis could not be restored by the administration of fresh serum from normal mice nor by guinea pig complement. Antigen-antibody complexes were rapidly removed from the blood with an average half-time of 11.9 minutes in normal mice. Complexes were cleared at significantly more rapid rates in mice previously sensitized to antigen.
Although not all the results can be explained on the basis of blockade the facts indicate that the RES does play an important but as yet undefined role in passive homologous anaphylaxis in the mouse.