Figure 2: C4d staining in 18 colon GVHD biopsies. Black bars represent colon biopsies that are positive for C4dand white bars represent colon biopsies that are negative for C4dstaining. A: Of the 18 patients clinically diagnosed with colon GVHD, 17 were positive for C4d (94%). B: Of the 8 patients with histologic GVHD present, 7 were positive for C4d (88%); of the 10 patients with histologic GVHD absent, all 10 (100%) were positive for C4d. C: Among the 7 patients with GVHD grade I or II, all 7 were positive for C4d (100%) and among the 11 patients with GVHD grade III or IV, 10 were positive for C4d (91%). D: Among the 14 patients who were sensitive to steroids, 13 (93%) were positive for C4d and among the 4 patients who were not sensitive to steroids, all 4 (100%) were positive for C4d.