Section II — lmmunogeneiics 



The effect of pregnancy and of estrogen stimu- 

 lation upon the functioning and the histological 

 appearance of the glands has been investigated. 

 Some of the transplants reacted normally to 

 pregnancy, with lactation and. on occasion, 

 suckling being observed. Histologically these 

 glands had the typical appearance of lactating 

 glands. The effect of estrogen stimulation will 

 be discussed. 



11.25. A Specific Alteration of Histocompatibility 

 Expression in the Progeny of a Homograft 

 Tolerant Male. Ronald D. Gutmann (Bet- 

 hesda U.S.A.) and J. Bradley Aust (Min- 

 neapolis, U.S.A.). 



The following results are from experiments 

 designed to study the effects of continual expo- 

 sure of maturating male germplasm in the mouse 

 to living cells of a foreign genotype. An adult 

 C3H male was rendered tolerant to A strain 

 tissue by the neonatal intravenous injection of 

 A splenic cells. Breeding this CsHtoierantA 

 male with (A ■ C3H)Fi hybrid females produced 

 a backcross population of mice which accepted 

 an (A X CsH)Fi hybrid mammary adenocar- 

 cinoma with an incidence of 91.3 per cent and 

 an 18th transplant generation A strain mammary 

 adenocarcinoma in 30.4 per cent of the cases 

 compared with 7.7 and per cent respectively 

 in the backcross control group. Other control 

 groups for the tumors were composed of A, 

 C 3 H, (A C 3 H)Fi, and (A C 3 H)F 2 hybrid 

 litters which accepted the tissue in accordance 

 with the expectations of the genetical theory of 

 transplantation based on susceptibility control- 

 led by multiple dominant histocompatibility 

 genes. Subsequent litters of backcross mice 

 sired by the C3H to i eranti ^ male were tested 

 with normal A, (A C 3 H)Fi, and (C57BL 



C.3H)Fi hybrid skin and accepted the A and 

 (A CsH)Fi hybrid skin in increased incidence 

 when compared with controls, but rejected the 

 (C57BL C3H)Fi hybrid tissue showing that 

 this change in histocompatibility relationship 

 has a donor-host specificity and is demonstrable 

 using normal as well as neoplastic tissue. 



11.26. Mutations of Histocompatibility Genes in the 

 Irradiated Mouse. Donald W. Bailey and 

 Henry I. Kohn (San Francisco, U.S.A.). 



Tail-skin grafts were exchanged among 

 (BALB/c rS C57BL/6$) Fi or the reciprocal 

 type hybrid mice, referred to here as CBFi 



and BCFi, respectively. Their fathers received 

 spermatogonia! X-irradiation (522 rads) or were 

 not irradiated. Of 2641 Fi mice skin-graft 

 tested, 30 were mutants. Of these, 26 showed a 

 gain in graft specificity (dominant), 3 showed a 

 loss in specificity (recessive), and only 1 showed 

 a loss and a gain in specificity (co-dominant). 

 The higher frequency of gains might be explained 

 thus: if the great majority of histocompatibility 

 genes or subgenes in the two parent strains were 

 identical, then by the laws of chance the gain 

 would be the most likely type of mutation de- 

 tected by our methods. 



Irradiation did not significantly affect the 

 mutation rate. The relative frequency of mutants 

 was: treated groups, 0.009 (BCFi) and 0.012 

 (CBFi); untreated group. 0.014 (CBFi). It was 

 noted, however, that many mutants occurred 

 as clusters within families, and thus presumably 

 arose in earlier generations. The high spon- 

 taneous mutation rate may therefore have mask- 

 ed the effects of irradiation. Nevertheless most 

 mutants had different specificities and thus must 

 have arisen independently. 



All observed histo-incompatibilities that were 

 adequately tested were shown to be inherited. 



11.27. Heritability of the Natural Immunity. Gyorgy 

 Szemere (Szeged, Hungary). 



Searching the genetic circumstances of the 

 natural immunity, the author has pointed out 

 that rats belonging to different races (brown, 

 laboratory white and Wistar) differ from each 

 other regarding their immunobiological titres — 

 namely the complement titre and bactericidal 

 properties — of their sera. Sera of brown rats 

 had the highest and that of laboratory white 

 rats the lowest complement titre and bacte- 

 ricidal activity. If Wistar and brown rats were 

 crossed, the complement titre and bactericidal 

 power of the hybrids' sera showed intermediate 

 values when compared with the titres of the 

 parents. 



It has been also pointed out that similarly to 

 the complement titre and bactericidal activity, 

 the sera of brown rats contained the greatest 

 amount of properdin, while sera of laboratory 

 white rats the smallest one. It was supposed, 

 therefore, that the properdin level, and other 

 factors which play a role in the formation of the 

 natural immunity, are different not only be- 

 tween species, but between races too. 



Crossing of brown and laboratory white 

 rats showed a surprising result. While the aver- 

 age properdin content of brown rats' sera 

 was 36.6 U./ml and that of laboratory white 



197 



