EXPERIMENTS IN HOMOGRAFT SUR\ I\ AI, 

 PRESENT INVESTIGATIONS 



The aim of the present investigation has been to clarify the position with 

 regard to the effect of irradiation on homograft sui\ ival, using marrow 

 infusion (and any other therapeutic measures which may l)e indicated) as 

 a means of prolonging animal sui\ival at lethal dosages. Thus we are 

 endeavouring : — 



(7) to establish a control value for homograft survival in the animal chosen, 

 i.e., in the rabbit. 



(2) to observe the effect of various dosage levels of irradiation on homograft 

 survival. 



(3) to establish a lethal dosage, against which it will be possible to judge the 

 effects of therapy. 



(4) to observe the effects of bone-marrow infusion on survival following 

 lethal irradiation (using homologous marrow). 



(5) to determine the effect on homograft survival in lethally-irradiated 

 rabbits of marrow infusions from the skin donors and from unrelated rabbits. 



Experimental Technique 



Rabbits of different skin colours (mostly black and white) have been used. 

 Under general anaesthesia pieces of whole-thickness skin, one-inch square, 

 have been removed from each ear and attached to similar defects. A series 

 of autografts has been completed to act as controls. This has been followed 

 by a series of homografts, initially without radiation dosage. The rabbits 

 have been used in pairs, one black and one white — each homograft has had 

 its own autograft 'control'. 



Irradiation has been carried out three days prior to skin-grafting; the 

 rabliits were enclosed in Perspex boxes for the purpose. The technique w^as 

 under the care of Dr. H. A. S. van den Brenk of the Peter MacCallum Clinic. 

 Details are as follows: — Half-value of 1 mm copper, 250 kV, 15 mA, an 

 added filter of 0-25 mm copper and 1 mm aluminium. 15 cm focal surface 

 dose and a 30 cm diameter open-port field. The free-air dose was 110 r 

 per minute. 



Interim Results 



Survival of the grafts has been estimated by frequent inspection, a definite 

 behaviour pattern becoming recognized. An autograft becomes slightly 

 swollen in the first three or four days, but remains quite soft. In the second 

 week there is desquamation of the superficial layers of the graft and in the 

 third week regrowth of hair commences. The graft remains soft and pliable 

 throughout. The first sign of rejection of a homograft is a loss of this soft- 

 ness — the graft becomes dry and gradually hardens over a period of two or 

 three days. Separation then slowly occurs, the skin defect being covered by 

 epithelialization from the edges and fibrous tissue contracture. Until 

 rejection commences, the behaviour of homografts has been indistinguishable 

 from that of their autograft controls. 



A graft is recorded as rejected at the first sign of hardness, \vhich is the 

 first difTerence noted between the homograft and its autograft control. 

 Table 1 shows the results so far obtained. 



All deaths occurred within 30 days of irradiation, tlic majority in the first 



70 



