An in vivo and in vitro analysis of systemic immune function in mice with histologic evidence of neural transplant rejection.

Histologic and immunocytochemical analyses of fetal neocortical tissue transplanted to the lateral ventricle of inbred adult mice indicate that this tissue survives transplantation well if the donor and host are isogeneic. The major histocompatibility complex (MHC) of the mouse is known as the H-2 locus. H-2-incompatible neural transplants (allografts), unlike their H-2-identical counterpart (isografts), are characterized by the presence of T cells comprising both major T-cell subsets and macrophages, and by a marked increase in the expression of both class I and class II (Ia) MHC antigens. These findings suggest a recognition of H-2 alloantigens by the host's immune system followed by an appropriate effector response. We report here our attempts to demonstrate systemic host sensitization to alloantigens in mice bearing H-2-incompatible intraventricular neural transplants. We measured the time to rejection of orthotopic skin grafts subsequent to neural transplantation, splenocyte proliferative responses to alloantigens in mixed lymphocyte cultures (MLC), and class I-restricted antigen-specific cytolytic T lymphocyte (CTL) activity. No significant differences were found in any of these tests of host systemic sensitization between mice with allogeneic neural transplants and those with isogeneic transplants or control animals. We conclude that intraventricular neural transplants, while recognized and affected by cells of the host's immune system, do not elicit a detectable systemic sensitization to class I H-2 alloantigens. Rejection of neural transplants may depend on sensitization to class II H-2 alloantigens, to so-called minor histocompatibility antigens, or some combination thereof.