Can I trypsinize and subculture macrophages?

No. Trypsin or Trypsin-EDTA will not work to detach and disperse macrophages. Macrophages are terminally differentiated cells that are limited in their ability to be subcultured or expanded. The cells can be gently scraped and passaged, but many cells will not re-attach and cell division will not occur to yield confluent, mature monolayers. Therefore, it is best to plate the number of vessels (plates, flasks, etc.) needed and to plan NOT to subculture them.