By further multiplying the percentage of the APC-positive cells in the Gate by the percentage of the Gate in PBMC, the relative contents of T-lymphocytes, B-lymphocyte and monocytes in the PBMC of colitis mice were found to be 73.8%, 16.0% and 8.7%, respectively (Fig. 3C), of which positive P-gp expression was observed in T-lymphocytes, B-lymphocytes and monocytes at proportions of 61.0%, 9.4% and 3.9%, respectively (Fig. 3D). Here, PGP is linked to colitis.