Which of the following statements is false? T-helper cells integrate the actions of the humoral and cellular immune responses. The humoral immune response is directed at antigens that have become established within cells. The humoral and cellular immune responses operate simultaneously. Cytotoxic T cells perform critical functions in the cellular immune response, and B cells produce antibodies in the humoral immune response. The humoral immune response produces antibodies, and the cellular immune response can destroy infected cells.