Hello Everyone,

I've been working with THP-1 cells and recently noticed some blackish clusters in the differentiated cells after 48 hours of differentiation (I've attached images of these differentiated THPs). To differentiate the cells, I use PMA at 100 ng/ml for 24 hours, followed by a 24-hour rest period in PMA-free media. Initially, I suspected a possible yeast infection, but the clusters didn't grow, and surprisingly, they even reduced after 72 hours post-differentiation. To be cautious, I discarded that batch of cells and started fresh.

However, in the new vial I revived from frozen stock, I observed something similar—reddish-black clusters(images of the undifferentiated THPs taken on the day of revival are also attached).

Has anyone else encountered something similar with their THP-1 cells? Any insights or advice would be greatly appreciated.

Thank you!