MODIFICATION OF RUNT DISEASE 365 



in the lymph nodes and large, prominent Malpighian corpuscles 

 in the spleens. 



Further delay of the secondary injection has not been exten- 

 sively studied. The technical difficulties of performing a satis- 

 factory intravenous injection become rapidly greater as pigmen- 

 tation deepens in this strain. Intraperitoneal injections of recipient 

 strain cells after the beginning of the "plateau period" have not 

 been beneficial. 



(2) Treatment with antiserum directed against DBAji spleen cells. 

 There is much evidence that cells of lymphoid origin are parti- 

 cularly susceptible to humoral cytotoxic antibodies in vivo (see, 

 for example, Garver and Cole, 1961). 



Although we were initially unsuccessful in our attempts to 

 confirm the finding of Siskind and Thomas (1959) that serum 

 injections from adult members of the recipient strain previously 

 sensitized to lymphoid cells of the donor strain could obviate the 

 onset of runt disease, this observation has since been reproduced 

 repeatedly. Our experiments usually consisted of giving a series 

 of 2 or 3 injections of o- 05 to o- 08 ml. of serum intraperitoneally 

 or intravenously to animals with impending runt disease beginning 

 on the second to fifth day of life. 



As portrayed in Fig. 12, a clear difference between the effective- 

 ness of serum from animals sensitized by means of DBA/ 1 skin 

 grafts and those sensitized with two injections of spleen cells in an 

 adjuvant mixture, as described above, is apparent. Cytotoxic 

 antiserum from animals sensitized by either of the two methods 

 used appeared to be capable of destroying the widely disseminated 

 donor lymphoid cells. A higher titre was apparently achieved by 

 the use of spleen cells and adjuvant, however, than by skin 

 grafting. 



Serum derived from spleen cell-adjuvant sensitized donors was 

 roughly as effective as sensitized cells when administered on the 

 fifth day of life. Of a total of 14 animals from four litters treated 

 with serum from spleen cell-adjuvant sensitized donors all 8 



