Acquired immunity involves lymphocytes and develops a slower response to specific microbes. It includes two types: the humoral response which produces antibodies, and the cell-mediated response involving cytotoxic lymphocytes. Memory lymphocytes provide a rapid response upon future exposures to the same antigen. T cells are activated by antigens presented on MHC proteins and perform cytotoxic functions or help coordinate immune responses by activating other cells. B cells are activated by contact with antigens and differentiate into memory B cells or antibody-secreting plasma cells. Antibodies neutralize pathogens or mark them for destruction.