I usually stain the ECM of blood vessels in a syngeneic glioblastoma GL261 model in C57BL6 mice using Collagen IV and/or Laminin without any issues. The signal is strong and colocalizes well with lectin.

However, in Rag gamma mice, the signal appears very weak or even absent when colocalizing with lectin, whereas it is clearly visible in non-perfused areas. Given that the same antibodies work well in C57BL6 mice, I suspect this might be due to steric hindrance caused by lectin binding rather than a technical issue.

Has anyone encountered a similar problem, or do you have any suggestions on how to resolve this? I am specifically interested in staining only the extracellular matrix of the vessels, so I am not considering markers like CD31, CD34, or podocalyxin.

Thanks in advance for your help!