MODIFICATION OF RUNT DISEASE 



367 



7r 



6 - 



^ 3 



>- 

 o 

 o 

 00 2 



Delayed Serum 

 Reequipment 



/J^- t \ No ser 



um 

 ment 



Serum injections 

 to 5 onimols 



2 3 4 5 6 7 8 9 10 12 14 



DAYS of AGE 



16 



22 



24 



Fig. 13. Weight-gain record of a litter of 7 newborn C57BL/6 mice, all of which 

 received 20 million DBA/i spleen cells intravenously on the first day of Hfe. 

 Five of these animals were treated on the fifth, sixth and seventh days of life 

 with 0-05 to 0'08 ml. of serum from adult C57BL/6 mice previously injected 

 with a DBA/i spleen-cell-in-adjuvant mixture. This favourable example shows 

 that such serum injections may be effective as late as the fifth day of life. 



III. Effect of some non-specific treatments 



This section deals with several forms of treatment, each of which 

 is well known to depress the activity of a variety of cells or, 

 indeed, to destroy them. Although lymphoid cells are parti- 

 cularly sensitive to any of these treatments the rapidly growing 

 newborn animal is generally much more vulnerable to such 

 cytotoxic agents and the revelation of differential effects between 

 the animal as a vehicle and its contained foreign cells may require 

 a fme regulation of dosage. 



(i) Cortisone. The retarding effect of cortisone on the homo- 

 graft reaction is known to vary considerably in strength between 

 species, being relatively weak in the mouse (Medawar and 

 Sparrow, 1956). A dose of 0-025 mg./g. of cortisone acetate was 



