130 IMMUNOLOGY 



characterized by an infiltration oL' neutroi)liilcs which actively 

 phagocytize the bacteria. This process does not lead to a local- 

 ization of the infection, but instead, the latter spreads throughout 

 the subcutaneous tissue in the form of a cellulitis. 



On tlie other hand, wlien they inject staphylococci into the skin 

 of previously immunized pigs the organisms are agglutinated into 

 masses of various sizes, and there is an infiltration of cells from the 

 subreticular layer of the cutis where vast numbers of "tissue 

 macrophages" have accumulated as a result of the previous intra- 

 cutaneous vaccination. ]\Iany of the clumps of bacteria are 

 ]^hagocytized by the large mononuclear pliagocytes and the infec- 

 tion remains localized ])ecause of phagocytosis and other factors. 



Local Fixation. — In discussing their results Cannon and 

 Pacheco (1930) call attention to the significant work of Opie 

 (1929) which enabled them to offer a rational explanation of the 

 observed phenomena. Opie studied the Arthus phenomenon and 

 concluded that when one injects an antigen into tissues containing 

 antil)odies the resultant antigen-antibody complex acts as a tissue 

 irritant, with a resulting inflammatory reaction characterized by 

 an infiltration of neutrophiles, edema, and the deposition of fibrin. 

 The small blood and lymph vessels are injured and become throm- 

 bosed. He obtained similar results when he injected antigen and 

 antibody simultaneously into the tissues of the rabbit. Of con- 

 siderable significance is his observation that antigen injected into 

 the skin of normal rabbits passes rapidly into the blood whereas 

 antigen injected into immune animals is fixed at the i>oint of injec- 

 tion. When along with these results one takes into consideration 

 the work on opsonification discussed in Chapter V, it would appear 

 that Cannon's explanation of tissue immunity to staphylococci 

 observed in the immunized guinea pigs may be summarized as 

 follows : 



Summary of Cannon's Work on Tissue Immunity to Staphy- 

 lococci.— 



1. As a result of intracutaneous vaccination there is a mobiliza- 

 tion of mononuclear phagocytes within the subreticular layer of 

 the cutis. 



2. There is an accumulation of antibody (opsonins, agglutinins, 

 etc.) within the tissues which is perhaps adsorbed by tissue cells. 



