I am doing T-cell priming assays and I noticed that there is an increase in the double positive CD4 CD8 and the double negative CD4 CD8 populations. Any possible explanations for this?
Dear Zaid, increase in DP population may be due to enhanced aggregation of T cells after activation. This explanation seems to me true, because we tried to use mix of T cells from CD4KO and CD8KO knock-out mice as responders in MLRs. Anyway, DP population (several percents of total viable cells) has appeared. Reasons for appearance of DN CD3 cells may be different. First (and the most probable), you see results of activation of gamma/delta T cells. Second, decrease in CD4 and CD8 density on the surface of T cells may take place after activation. This phenomenon may require special study.
There are also several studies associating co-receptor downregulation (generating DN cells) with a tolerant state. Perhaps your experimental conditions are more tolerogenic than priming.