Histopathologic evidence of GVHD in animals that received a transplant and no immunosuppression (R.1-R.3). (A) Photomicrographs of hematoxylin and eosin (H&E) staining of the lungs, liver, and colon show GVHD in untreated animals. These studies used an Olympus BX51 microscope (Olympus America), using a 10×/0.40 UPlan Apo lens (Olympus). Slides were mounted with Permount solution (Sigma-Aldrich) and photographs were taken with the Spot RT Slider imaging system (Spot Imaging Solutions). Image analysis was performed using Spot Advanced Version 4.6 (Spot Imaging Solutions), and image processing was performed using Photoshop CS4 extended v11.01 (Adobe). (Row 1) A normal control that did not receive a transplant; (row 2) R.12, an irradiation control; (row 3) R.1; (row 4) R.2 (inset in the colon photomicrograph shows an example of CD3 staining of this organ); (row 5) R.3. Bar = 100 μm. (B) Untreated transplant recipients demonstrated significantly higher GVHD histopathology scores compared with either normal controls or CoBS-treated transplant recipients. Combined histopathologic GVHD scores for controls that did not receive a transplant (black), recipients of transplants without immunosuppression (blue), and recipients receiving CoBS immunosuppression (red) are shown. The histopathologic GVHD grading was performed by a pathologist blinded to the treatment regimens that the animals received. Individual tissue scores were from 0 (no GVHD) to 4 (severe GVHD), and the combined score was the sum of individual scores from the lung, liver, and colon.