The effect of a low protein diet on the immunogenic activity of murine peritoneal macrophages

The activity of resident and exudate peritoneal macrophages from mice maintained on a low protein diet (4% casein initiated at weaning) was assessed in a variety of assay systems which examined aspects of macrophage 'immunogenic' function in vivo and in vitro. Antigen-pulsed macrophages from malnourished mice triggered secondary IgE and IgG responses following intraperitoneal inoculation into pre-immunized syngeneic recipients. Similarly, intraperitoneal transfer of low numbers of these cells successfully primed immunologically naive syngeneic mice; in both cases, the activity of macrophages from malnourished mice could not be distinguished from these derived from normal animals. Examination of uptake and breakdown of radio-labelled antigen revealed normal rates of phagocytosis, and a brief lag in the early phase of degradation, relative to control macrophages. Antigen-pulsed macrophages from malnourished mice were severely impaired in their capacity to trigger the proliferation of antigen-primed T cells in vitro.