Immunoreactivity of long lived H-2 incompatible irradiation chimeras (H-2d leads to H-2b).

Allogenic irradiations bone marrow chimeras made according to a new protocol with unmanipulated bone marrow are long lived, healthy and stable full chimeras (H-2d leads to H-2b). Their immunocompetence is split. Alloreactivity measured by skin graft rejection and mixed lymphocyte culture is within normal range. In contrast, major histocompatibility complex (MHC)-restricted T-cell-dependent primary responses against sheep red blood cells (SRBC) or viruses are clearly deficient. The quantitative difference in immunocompetence is at least of the order of ten-to thirty-fold. The implications of the findings for lymphohaemopoietic reconstitution of immunodeficient patients are briefly discussed.