Increased blood vessel density as seen with collagen IV and CD31 immunohistochemistry. Representative collagen type IV and CD31 immunohistochemical stains from the lumbar spinal cord region. In the white matter of the naïve rats, collagen IV and CD31 blood vessels are found. In the EAE rats during the relapse phase there are more collagen IV positive blood vessels seen in the inflamed white matter. CD31 immunohistochemistry shows a similar increase in blood vessel density. Interestingly in some of the blood vessels, the CD31 staining became much more diffuse (arrows) and not as prominent as compared to the naïve rats.