Immunological reactivity between chimeric cattle twins. I. Homograft reaction.

The response of chimeric calves to grafts of cotwin skin was examined both by direct observation of the fate of the graft and by collection of lymph from the lymph node which drained the grafted area. Whilst grafts of body skin exchanged between 16 pairs of twins survived for longer periods than did grafts transferred between unrelated calves, all of the former had been rejected after 10 weeks. Secondary grafts of cotwin body skin were rejected significantly faster. In contrast, grafts of auricular skin exchanged between cotwins survived indefinitely in some instances despite the rejection of simultaneously transferred body skin. The magnitude of the blast cell response observed in efferent lymph in the case of grafts exchanged between cotwins was generally intermediate between that observed in responses to allografts and control autografts. However, an early peak of blast cell response which occurred some 50 hr after placement of allogeneic grafts was not observed in response to cotwin grafts.