These results indicate an association between immunosuppressive therapy and the onset of diarrhea in Whipple's disease and thus support the concept that immunologic factors play a role in disease pathogenesis. Further investigation on the interaction of the immune system and Tropheryma whipplei infection are required to understand the factors contributing to the clinical manifestation of this rare disorder and possibly to introduce preventive interventions.

Our data demonstrate a persistent defect of the cellular immune response with decreased serum concentrations of IL-12p40 and TNF-alpha and decreased IgG2 levels in a large group of WD patients. These data support as in vivo finding the results obtained in previous investigations with stimulated monocytes/lymphocytes. The isolated decrease in IL-12p40 may hint at possible defects in the IL-12/IFN-gamma promoter system.