Antiserum-induced growth of axons across lesions of the adult rat brain.

Growth of axons across lesions of the adult rat brain occurred when the lesions were treated with a heterologous antiserum developed against lesioned areas of the brain. Rabbits were immunized with blocked dissected damaged rat brain plus adjuvant. The antiserum was prepared by ammonium sulfate precipitation of the immune rabbit sera followed by pepsin digestion to prevent complement-mediated damage to the recipient rats. Rats treated with the antiserum had dense cellular bridges crossing the brain lesions which contained axons. The axons within the dense cellular bridges were newly formed, since they were observed to pass through the center of paper rings which were implanted into the lesion. Individual axons were traced from one side of the lesion, through a dense cellular bridge, and into the tissue on the opposite side of the lesion. Rats lesioned in a similar manner, but treated with either phosphate-buffered saline or normal rabbit serum displayed no such growth. In addition, the limited axonal growth observed was enhanced by increasing the concentration of the antiserum administered. Thus, the antiserum induced the formation of dense cellular bridges and the growth of axons across lesions of the mammalian central nervous system.