Lymphocytic Response to Tissue Transplantation 101 



immunologic phenomena in the rejection of homografted tissue was clearly 

 established, by the accelerated rejection of second-set homografts, in compari- 

 son to first homografts, and by the observation that an increase in the amount 

 of tissue introduced in a primary graft can cause a greater degree of accelera- 

 tion of rejection of a second one. Possible relations of the infiltrating lym- 

 phocytes to such immunologic processes were discussed in this paper. Similar 

 observations on the host tissue reaction were reported in the study of l>ill- 

 ingham, Krohn. and Medawar, who also found lymphocytes the most abun- 

 dant member of the invading mass of leukocytes of rabbit skin homografts. 8 



Darcy also studied the cellular reaction to homografts in the rabbit, in 

 this case homografts of the submaxillary gland. He found that the cells in- 

 vading the graft included small lymphocytes and a large number of cells 

 stained strongly with pyronine, identified as mature and immature plasma 

 cells. The numbers of lymphocytes and of mature and immature plasma cells 

 present in the graft at various stages after implantation were studied in the 

 case of both first- and second-set grafts. Attempts to correlate the concentra- 

 tion of each of the cell types with the speed of graft destruction, the amount 

 of grafted tissue destroyed, and the difference between reactions to first and 

 second homografts led the author to conclude that the plasma cells that 

 infiltrate the grafts are not a significant cause of their destruction. The same 

 appeared to hold, although with less evidence, for the lymphocytes. 1 ' 



In a study of human skin homografts, Rogers and colleagues observed 

 the occurence of eosinophilic leukocytes in the blood and at the site of the 

 homografts. They found some increase of eosinophils both in the blood and 

 at the site of the orraft, but this was of maximal intensity after the homosraft 

 had sloughed and only the dermis remained intact. 10 



In the case of tumor transplants, Toolan and Kidd inoculated mammary 

 carcinoma and lymphosarcoma of C 3 H strain mice into A mice. In tumors 

 which regressed, they found a gradual shrinking of the tumor cells and in- 

 creased basophilism of nuclear and cytoplasmic constituents, leading to com- 

 plete breakdown of these cells. This sequence was found never to begin 

 until "lymphoid elements" of the host accumulated and attached themselves 

 to the peripheral cells, often curving like crescents around them as they 

 shrank, while adjacent tumor cells without attached lymphocytes remained 

 unaltered. In the case of mice in which such tumors had formerly grown and 

 regressed, there was earlier arrival of lymphocytes, after second implanta- 

 tion, and correspondingly earlier regression of the tumor. 11 



Cellular Changfs in Lymph Nodes Draining Sites of Homografts 



The reaction of the lymphatic system to implanted tissue has also been 

 studied by histologic examination of lymph nodes draining sites of implanta- 



