Studies on the Cx-reactive protein. II. Inhibition of the Cx-reactive protein response in rabbits by blockade of the reticulo-endothelial system.

It has been found that normal rabbits respond to the intravenous administration of thorotrast by producing Cx-reactive protein. The amount of Cx-reactive protein produced in response to successive injections of thorotrast progressively diminishes until finally little or no further Cx-reactive protein production can be elicited. The reticulo-endothelial system is believed to be effectively blocked at this point. When such "blocked" rabbits are injected intracutaneously with Cx-reactive protein incorporated in adjuvant they produce significantly less Cx-reactive protein than the amounts elicited by the same stimulus prior to thorotrast treatment. They also fail to develop the characteristic inflammatory reaction seen in the control experiments. In addition, rabbits whose reticulo-endothelial systems are loaded with thorotrast respond to dermal infection with Type I pneumococcus by producing only very small amounts of Cx-reactive protein in comparison with the control animals.