Immunohistochemistry for DNA repair proteins and 3-nitrotyrosine in colon biopsies. Expression of MLH1, MSH2, MSH3, XPA, and APE1 was similar in the colon biopsies obtained from subjects who did not receive a transplant with no relevant medical history (top) and from patients who received an allograft (bottom). There was no immunostaining for 3-nitrotyrosine in either group. Representative photographs are shown (× 600). Image acquisition performed as described for Figure 1.