To provide a method improved for treating disease states in which pathogenic cell populations such as cancer cells are present.

The improved method is to enhance specific elimination of pathogenic cell populations mediating endogenous immune response in preliminarily immunized host animals having the populations therein, in which a member of the cell populations has an accessible binding site for a ligand, and the method includes a step of administering to the host a composition containing an immunogen or a ligand/hapten conjugate, the immunogen or hapten being recognized by an endogenous antibody in the host or recognized directly by immune cells in the host, wherein the method further includes a step of allowing existent immunity to come out by preliminary immunization of the host using an immunogen or immunogenic hapten/carrier conjugate and a TH1-biasing adjuvant. Preferably, the method further includes a step of administering a treatment factor selected from the group consisting of cytocidal agents, neoplasm invasiveness enhancers, and chemotherapeutic agents.