[Chimeras of the spinal cord between quail and chicken. A new experimental model for studying demyelinating diseases].

Avian chimaeras in which definite fragments of the neural primordium of chick embryos are isotopically and isochronically substituted, at the brachial level, by their counterpart from quail have been constructed at embryonic day 2 (E2) and allowed to hatch. Hatched chimaeras displayed seemingly normal motor behaviour (including feeding, running and flying) indicating that the establishment of the neuronal circuitry occurred normally. However, during the second or third month of life, the chimaeras developed a neurological syndrome characterized first by paralysis of the wings and then of the legs. The spinal cord and peripheral nerves and ganglia originating from the graft exhibited pathological signs including expression of class II MHC antigens by capillary endothelial cells, rupture of the blood-tissue barrier, leukocyte infiltration of the nervous tissue and demyelination. This can be interpreted as the rejection of the graft. Interestingly, this process resulted in sensitisation of host's T cells to neural antigens and in spreading of the lesions to the host's CNS, thus creating in the chick an autoimmune disease directed toward its own nervous system.