Cellular Reactions to Soluble Foreign Materials in Rabbit Knee Joint Cavities **

For well over half a century, since the days of the imaginative and enthusiastic genius, Metchnikoff, it has been known that foreign materials cause inflammation.' When the material is a splinter in our finger, we take it for granted that the body will mobilize its phagocytes to react to the foreign material. Less well known is that soluble foreign proteins and polysaccharides ("antigens" in usual biologic reference) regularly induce a similar prompt outpouring of polymorphonuclear leukocytes. The mechanism of this local reaction, which has been termed "norergic" as contrasted with "allergic" inflammation,' has received surprisingly little attention when contrasted to the vast literature on the immunologic response to foreign materials. Lack of curiosity about the mechanism of this inflammatory reaction probably stems from its generally mild and transient nature. However, this is not always true since biologists who use casein or glycogen to produce a polymorphonuclear peritoneal exudate are taking advantage, perhaps, of this type of reaction to foreign material. During the course of some observations on inflammation and infection in rabbit suprapatellar bursae, Metchnikoff's cellular reaction to foreignness, so well described by Clark and Clark 30 years ago,8 was re-encountered. Synovial membrane seems a particularly suitable site for observations on cellular inflammatory exudate. The observations were conducted in an effort to understand more about the nature of the acute inflammatory response to soluble materials, as well as its possible relation to the immune response elicited by these materials.