sqo local and tissue immunity 



more susceptible cells. At all events I see no evidence for believing with Besredka that 

 certain forms of active immunization ''close the specific portal of entry" — a concep- 

 tion that has shifted in his own explanations to "desensitization of the specifically 

 susceptible cells." It should be pointed out that he has confused the two ideas of 

 portal of entry and locus minoris resisientiae which are far from interchangeable. 



THE RETICULO-ENDOTHELIAL SYSTEM 



The reticulo-endothelial system of cells seems particularly concerned in active 

 phagocytic opposition to infectious agents. Certain components of this system, the 

 clasmatocytes (histiocytes, polyblasts, rhagiocrine cells, or tissue macrophages), can 

 be selectively marked by vital dyes and shown in the case of localized streptococcus 

 infections to be actively responsible and productive of marked protection when 

 increased in a given area (Gay and Morrison;' Gay,^ Gay, Clark, and Linton^). 

 They may actually be collected in one pleural cavity and attracted for purposes of 

 protection to the other pleural cavity. 



These same cells may also eventually be shown to be responsible for more durable 

 conditions of active immunity. Ledingham,'' for example, regards them, rather 

 than the epidermal cells, as responsible for vaccine immunity. 



The questions of antibody formation and local immunity are closely involved. 

 Local immunity may undoubtedly occur without the demonstrable presence of anti- 

 bodies, but I do not believe the two conditions are by any means mutually exclusive 

 as Besredka would seem to think. And again, the reticulo-endothelial system seems 

 implicated in the more generalized formation of antibodies, to judge from the evidence 

 that the "blockade" of these cells by dyestuffs (Gay and Clark,^ Jungeblut and 

 Berlot^) inhibits antibody production. Everything points, then, with increasing em- 

 phasis to the reticulo-endothelial system as forming the background of immunity 

 processes; the cells comprising the system are ubiquitous; certain of them, the mono- 

 cytes and the histiocytes, are mobile; both endothelial and reticular cells have re- 

 peatedly been shown to have direct phagocytic activity against bacteria, and those 

 cells which may be stimulated or blocked by dyestufifs are seriously concerned with 

 antibody formation. Blockade furthermore seriously affects the direct protective 

 function of the specific cells in both bacterial and protozoan infections (Meyer,? 

 Jungeblut^). 



The present tendency in histological studies would seem to indicate that the 

 monocytes of the circulating blood and the histiocytes (clasmatocytes) of connective 

 tissue are not only connected in origin but may actually be transformed into one 



' Gay, F. P., and Morrison, L. F.: loc. cil.; J. Infect. Dis., 33, 338, 1923. 



2 Gay, F. P.: /. Immunol., 8, i. 1923; Physiol. Rev., 4, 191. 1924; Arch. Path. &' Lab. Med., i, 

 590. 1926. 



3 Gay, F. P., Clark, A. R., and Linton, R. W.: loc. cit. 

 "Ledingham, J. C. G.: Brit. J. Exper. Path., 8, 12. 1927. 



5 Gay, F. P., and Clark, A. R.: J.A.M'A., 83, 1296. 1924. 



* Jungeblut, C. W., and Berlot, J. A.: J. Exper. Med., 43, 613. 1926. 

 'Meyer, H.: Ztschr.f. Hyg. u. Infektionskrankh., 106, 124. 1926. 



* Jungeblut, C. W.: ibid., 107, 357. 1927. 



