Using Western blotting, we found that case-patients with Whipple disease were significantly more likely to be seropositive than controls with diarrhea (Figure 2) for IgG (7/8 vs. 5/25; p = 0.001) and IgM (7/8 vs. 1/25; p<0.001) and than controls without gastroenteritis for IgG (5/20; p = 0.004) and IgM (1/20; p<0.001). Here, CD40LG is linked to Whipple disease.