cell-mediated immunity, immune response that does not involve antibodies. Cell-mediated immune responses can involve the destruction of infected cells or cancer cells by CD8 T cells or natural killer cells. CD4 T cells also provide protection against different pathogens via activation of CD8 T cells and secretion of cytokines. Primarily directed at microorganisms that survive in phagocytes and microorganisms (viruses and bacteria) that infect nonphagocytic cells. Also called cellular immunity.
