Immunological status and longevity of radiation-chimaeras

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Abstract
(1) Homologous radiation-chimaeras, produced by irradiating CBAH mice with 950 rads of X-rays and resuscitating with Ah myeloid tissue, usually die within 4 months of "secondary disease". Bone marrow from adult AH mice is more strongly productive of "secondary disease" than spleen from 5 to 10-day-old AH infants. (2) Secondary disease was not seen when C3HH infant spleen was given to restore C3H x 101.F1 irradiated mice or the F1 infant spleen to irradiated C3HH. (3) When AH, CBAH and CBA x A.F1 were each used as irradiated recipients and donors of adult bone marrow, the F1 approximated much more closely to a universal donor than universal recipient for the avoidance of secondary disease. (4) Those animals from the preceding group which survived 6 months or more were skin grafted with the three types of skin. The responses of the chimaeras in terms of "take" of these skin grafts were the sums of responses of host and donor elements of the chimaeras. The evidence from these and other experiments is reviewed with the conclusions (1) that in homologous chimaeras the host is tolerant of the donated grafts of myeloid tissue, (2) that if the histoincompatibility between graft and host is marked the graft may react against the host to produce "secondary disease"; (3) that, if the histoincompatibility is slight or if immature myeloid tissue is given, "secondary disease" is attenuated[long dash]the roles of "partial tolerance", "immunological paralysis" and "enhancement" of the graft versus host reaction are discussed.