Below are a few tips we recommend if you encounter any issues during initial culture:
• For the first 2-3 passages, grow cells in media containing 20% FBS and no antibiotics.
• Do not allow cells to reach 100% confluency. Please check the cells as regularly as possible.
• The cells should not be grown in 20% FBS for too long. Use media with 10% FBS after 2 or 3 passages.
• When making frozen stocks, continue growing additional cultures in case there is a problem with the frozen stock.

If you are working with THP1 cells in particular, here are a few additional tips:
• THP1 cells need to be passaged between 3 x 10⁵ and 7 x 10⁵ cells per mL (we recommend 5 x 10⁵ cells per ml). Below this, your cells will take a long time to grow and above 2 x 10⁶ cells per ml you may have toxicity.
• Between each passage, do not centrifuge the cells. THP1 cells grow better in conditioned media, therefore when passaging cells, leave 1 – 2 ml of the old media and add fresh media on top. Do not leave more than 50% of conditioned media as the cells will not have enough nutrients to properly grow.

Handling of cells upon arrival