It involves T cells, the T cells exposed to certain antigens undergo division that generate cytotoxic t cells and memory. The cytotoxic T cells find and attack the bacteria , fungi, protozoa or foreign bodies or tissues that contain antigenic material. The cytotoxic Tcells can locate and rapture the antigenic cell membrane and can destroy the invader by secreting a poisonous lymphotoxic substance. Memory T cells remain on reserve ready to respond if the antigen returns at a later date.