To detect a humoral immune response to E . Coli bacteria, you would measure __ a. cytotoxicity of virus -infected cells in the lung. b. dividing T cells in the draining lymph nodes. c. plasma cytokine levels. d. serum antibody titer.

To detect a humoral immune response to E. coli bacteria, you would measure:<br /><br />d. serum antibody titer.<br /><br />The humoral immune response involves the production of antibodies by B cells. Measuring the serum antibody titer, which is the concentration of antibodies in the blood, is a direct way to assess this response. This measurement indicates the level of immunity against E. coli bacteria and helps in understanding the effectiveness of the immune response.