392 J. F. A. P. MILLER 



Adoptive immunity 



Four neonatally thymectomized C3H mice bearing healthy Ak 

 skin grafts were injected one month after grafting with C3H 

 lymphoid cells from non-thymectomized donors presensitized 

 against Ak tissues. In all four mice a severe reaction was evident 

 in the skin graft 12 days after the injection of sensitized cells. 



Thymus grafting 



Four neonatally thymectomized (Akx T6)Fi mice grafted 

 two weeks after birth with an intact day-old Ak thymus were 

 grafted at 8 weeks of age with skins from C3H, C57BL, BALB/c 

 and DBA/2 donors. In all four mice DBA/2 and BALB/c skins 

 were rejected between 15 and 30 days after grafting, C57BL 

 between 30 and 35 days and C3H between 35 and 40 days. These 

 data suggest, but do not prove, that immune reactivity might be 

 restored to neonatally thymectomized mice by thymus grafting. 



Discussion 



It has been shown that thymectomy of the neonatal mouse is 

 associated with severe depletion in the lymphocyte population 

 and serious immunological defects in the mature animal. One is 

 tempted to suggest that during foetal life, and possibly even in 

 postnatal life, the thymus produces the originators of immuno- 

 logically competent cells which mature and migrate to other sites 

 (Miller, 1961). The results presented here provide strong support 

 for the predictions made recently by Burnet (1961) and Auerbach 

 (1961) that the thymus may represent the major primordium of 

 the immunological system. They are in harmony with the recent 

 experimental findings of Mueller, Wolfe and Meyer (i960) that 

 neonatally bursectomized chicks could not produce antibodies, 

 and of Archer and Pierce (1961) that rabbits thymectomized at 

 birth subsequently failed to show any antibody response to bovine 

 serum albumin. 



One basic feature of the states of immunological failure, 



