a kind of cell helps destroy pathogens
pathogen is infectious_agent. genetically_engineered_viral_pathogen is viral_agent. genetically_engineered_viral_pathogen is genetically_engineered_pathogen. pathogen is microorganism. gram_negative_cell_wall is bacterial_cell_wall. cancer_cell is dangerous_thing. genetically_engineered_bacterial_pathogen is genetically_engineered_pathogen. toxic_substance is human_pathogen. natural_killer_cell is lymph_cell. killer_t_cell is t_cell.