Thanks Waseem for your thoughts, I got your points, but these two steps didnt happen in my cells. For my specific cell lines, I didn't wash during my thawing; the debris and dead cells disappeared before I passage them. that's why I assume something special happened.

Hi Shiqiu, I have seen similar things with thawed epithelial cells, but less so with endothelial cells.

I doubt that this is MMP driven since the cell fragments are composed of lipids, proteins, nucleic acids.

I assumed that since most epithelial cells have robust endocytosis, the cell fragments are being taken up by live cells.

I could also see little blebs inside and around the live cells. I attributed this to endocytosis of the cell fragments.

Dear Steingrimur: thanks for sharing your inspirational idea and observation. I agree with you on MMP, since there is no proof about MMP from B cell derived tumour cell lines i am working on. However, i am not sure whether endocytosis invovle in this process, regarding the similar size of most dead cells.

Meanwhile, the ratio between live cells and dead cells (including debris) seems stable during long cell culture, and this ratio is variable among different cell lines. How interesting!

Hi Shiqiu, this is interesting! One thing that I overlooked in my previous answer is the presence of FBS in the culture media.

FBS has lipoproteins and serum albumin that incorporate lipids from the media. Most cells have endocytic lipoprotein receptors and serum albumin mostly passively exchange lipids with cells. .

I'm not familiar with the endocytic arsenal of B cells, but I would not be surprised that they are hungry for cell fragments. Especially since cell fragments expose phosphatydyl serine.