Immunological relationships of a filterable agent causing a leukemia in adult mice. I. The neutralization of infectivity by specific antiserum.

The antigenic character of a filterable agent which induces leukemia in adult mice has been investigated. Mice and rabbits injected with filtrate yielded sera which specifically neutralized infectivity of the agent. Normal sera, sera from mice with other neoplasms-including leukemias from which no causative agent has as yet been obtained,-and sera from leukemic human beings contained no such neutralizing antibody. A formalinized vaccine prepared from filtrates of leukemic spleens induced a significant degree of immunity against the agent, approximately 80 per cent of the vaccinated mice being immune on challenge with it.