Alteration of the specificity of antitumor antisera by the use of passively administered antibody.

Antispleen antibody was produced in burros by immunization with C57BL/6 spleen lymphocytes. The effect of passive administration of this antiserum in inhibiting antibody production to antigenic determinants common to both C57BL/6 lymphocytes and EL4 tumor cells was studied. Simultaneous immunization with EL4 cells and antispleen antibody resulted in specific alteration of anti-EL4 activity so that cross-reactivity to splenic lymphocytes was diminished. These results demonstrate the potential usefulness of passive antibody administration in altering host immunological responsiveness to antigenic determinants on tumor cells.