The effect of bursectomy on the adoptive transfer of resistance to Marek's disease.

Immunization with inactivated viral antigens protected chickens against Marek's disease. Non-immunized chickens could be protected by injections of spleen cells but not of serum from immunized, histocompatible donors. Chickens rendered agamma-globulinaemic by bursectomy and irradiation could also be immunized against Marek's disease by inoculation with viral antigens, but spleen cells from these immunized, bursectomized and irradiated donors did not confer protection on the recipients into which they were injected. It was concluded that, although in the bursectomized, immunized donors cell-mediated immunity alone was able to provide a fair degree of protection against Marek's disease, the protection afforded against the disease by spleen-cell transfer was at least partly attributable to the transfer of antibody-producing cells, and that humoral immunity, while not being an absolute requirement for resistance, is normally an important component of the resistance mechanism.