I was going through this webpage and I found the following lines:
We hypothesised that despite unimodal distribution of CD4 co-receptor on naïve CD4 T cells they are not homogenous in their function.By testing naïve CD4 population from mice and humans expressing highest and lowest (~10%) levels of CD4 in a variety of functional assays we find that indeed naïve CD4 cells with high CD4 levels respond much better to activation and survive more easily post-activation.
Now what does "CD4 level" means? How is the CD4 receptors distribution obtained? With repect to the value of which feature is it obtained?(If you are not able to understand the last question, let me know, I will try to explain more in details)