Lymphocytic Response to Tissue Transplantation 107 



used, or when tissue fragments were injected subcutaneously, or when tissue 

 fragments had been frozen and then thawed or dried.' 1 ' 



In another approach to the demonstration of the association of lymph 

 node cells with the transplantation immunity of skin homografts, Voisin 

 and Maurer obtained cells from lymph nodes and peritoneal exudates 

 (largely macrophages) of guinea pigs that had received skin homografts 

 eighteen days previously. These cells were transferred to some of a group of 

 guinea pigs that had received skin homografts three days earlier, from the 

 same animals which had been the donors of the earlier skin graft. The other 

 skin-grafted guinea pigs served as controls. On comparing the appearance of 

 the skin grafts in these two groups between the seventh and eleventh days, 

 it was found that the grafts of two thirds of the recipients injected with 

 lymph node or peritoneal exudate cells were in worse condition than were 

 the controls. 40 



In yet another approach to the role of cells of lymph nodes regional to the 

 site of a skin homograft. Brent has described a series of experiments in 

 guinea pigs. In these experiments skin was grafted from donor guinea pigs 

 to recipients. Subsequently cells of the lymph nodes regional to the site of 

 the graft were obtained and were injected intradermally into the donor 

 guinea pigs. These injections were found to produce local inflammatory 

 wheals, indicating that a specific reaction had occurred between the lymph 

 node cells and the tissue antigens of the donor. 41 



Finally, lymph node cell transfer of tissue transplantation immunity has 

 been studied in connection with the homotransfer of lymph node cells them- 

 selves. In the work with transfer of lymph node cells incubated in vitro 

 with soluble material derived from Shigella paradysenteriae , referred to 

 above, it was found that the usual appearance of agglutinins to Shigella 

 after the transfer of such cells could be prevented by prior injection of the 

 recipients with pooled leukocytes from donor animals. In order to bring 

 about this suppressive effect on the lymph node cells, it was necessary to 

 inject an adequate number of leukocytes at an appropriate interval prior 

 to the lymph node cell transfer. These and other considerations suggested an 

 immunologic mechanism of this suppressive effect, analogous to the accel- 

 erated rejection of a second skin graft of a given donor to a given recip- 

 ient. 4 - iS In these terms the recipient animal was regarded as having been 

 actively immunized to the tissue transplantation antigens of the donor ani- 

 mals by the prior injection of the leukocytes. It was of interest to see whether 

 in this situation the tissue transplantation immunity — i.e., the suppressive 

 effect on transferred lymph node cells — could be transferred by appropriate 

 lymph node cells. Accordingly, rabbits were injected in one hind foot pad 

 with blood leukocytes pooled from a set of prospective lymph node cell 



