36 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



The marked difference already observed in the reactions toward azo dyes of 

 these two great classes of connective-tissue cells constitutes, then, not an example of 

 the reputed fact that actually different structures arc tinged in these two cell cate- 

 gories, but of a fundamental difference in the biologj' of the two cells. It would 

 seem appropriate, consequently, for us to rehearse very briefly the striking biological 

 differences which make their imprint in the distinctive vital-staining effects which 

 characterize the two cells. 



CHARACTERISTIC DIFFERENCES IN THE MACROPHAGE AND FIBROBLAST RESPONSE 



TO AZO DYES. 



We have already had occasion to remark on the success with which one may 

 obtain by appropriate dosage deposits of the vital dyes only in the macrophage 

 series of connective-tissue cells. We refer to the initial great engorgement of these 

 phagocytes in the early stages of acute staining with high dosages of positive dye- 

 stuffs of the azo class and to the pure macrophage crystalline deposits which can be 

 obtained by excessively dilute dosages with the crj^stallizable dyes. Both of these 

 phenomena seem clearly referable to the increased power of absorption or more 

 permeable character of the macrophage cells. The lesser permeability of the fibro- 

 blasts also accounts for the generally smaller deposits which are produced in these 

 cells under all conditions of acute vital-dj-e dosage which are sufficient to affect both 

 types of cell. It is indeed possible that it is the slower entry alone which produces 

 not only smaller, but denser, concretion-like, or crystalline deposits in these cells, 

 for we have seen that the pure-crystal picture can be produced in macrophages if 

 only the rate of entry of dye into the same be very gradual, as is obtained by the 

 lowest dosages which we have employed. And we have also seen that the use of 

 dyes with a great diffusion speed (e. g., dye T 148) succeeds in establishing quickly 

 a typical vacuolar segregation-apparatus in fibroblast cells. 



Though slower to respond to the vital dye, the fibroblasts ivill, however, under long- 

 continued dosage, invariably increase their dye-content and, with a chronic dosage, may 

 come to resemble in their deposits so completely the macrophage cells that marked separa- 

 tion in the ''dye bodies" in accordance with cell types no longer obtains (figs. 82, 83). 



Protocol: Rat 18-1, injected intraperitoneal^ with a 0.5 per cent solution of dye T 148, 

 January 31 to February 25, 1. c. c. each day. 



February 26: Animal is stained a bright crimson. Subcutaneous tissues are bright red. Under 

 the low-power the dye-content of all cells is seen to be large and is of a deeper color than usual for 

 even heavy stains with this dye, although here the vacuoles appear pink only, and in some cases a 

 pale yellow-pink. Both elastic and white fibers seem more yellow in color than is normal. Cell 

 types are not distinct under the low-power. 



Macrophages can be distinguished under the oil by their dye deposits as well as by the general 

 cell morphology. This distinction is not, however, striking, and types are often somewhat obscure 

 without careful study of the individual cells. Dye vacuoles fill the cytoplasm of the macro- 

 phages. These vacuoles are uniform in size for a given cell and usually are about the size of mast-cell 

 granules. Rare macrophages have vacuoles of considerable size. The color of the vacuoles is also 

 variable. They are perhaps slightly deeper in shade than the fibroblasts, but some are very pale, 

 almost without color. Small concretions are often present in the vacuoles. The most definite, 

 points of differentiation between these and fibroblast vacuoles are their shape, which is always 

 round (no linear structures — "thread bodies" — are present), and their uniformity in size (fig. 83). 

 Neutral red 1 : 5,000 stains the vacuoles in macrophages electively a slightly deeper red than the 

 vacuoles of fibroblasts. No linear structures are found in these cells. Janus green stains normal 

 mitochondria. 



