Dear Gottfried, 

In terms of macrophages, once they are in culture one can only use them for a certain passage number, depending on their origin, as these cells are suffering from genetic drift. RBLs per instance have an average passage number of below 20, one passage is around 5 days. I am not a mast cell expert, however I know that also there it depends at the origin of the mast cells, skin mast cells, for example exceed not longer than 21 days in culture. mast cells derived from the bone marrow it the peripheral blood can be in culture over 8 weeks. I hope I could help you. 

Best Marietta 

Article Induction of differentiation of human mast cells from bone m...

Gottfried, are you talking about primary macrophages? Isolated from what tissue and what species? If you mature primary monocytes (human) into macrophages, they dont really divide a lot, and can't be kept in culture for very long (2 weeks, maybe slightly more) without loosing their functionality.

Both peripheral monocyte-derived macrophages and cod-blood or bone marrow-derived mast cells have finite life time under in vitro culture conditions.  These primary cultures can be used only for several passages.  Transformed human mast cell lines such as HMC-1 (originally isolated from patients) and HMC-1 5C6 can be maintained in culture for ever.  A cautionary note is that these mast cell lines lack many normal mast cell characteristics.   

Thank you for the great comments from very near-by (!) and from very far. I'm a clinician and I basically wonder if mast cells dictate monocytes/macrophages more than the other way round. Since mast cells seem to have a t1/2 of 1,7 years... New answers of in vivo study of Masat cells are to be found in Laurent Reber (2012): http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3572764/pdf/nihms412476.pdf or his more recent promising:

J Vis Exp. 2015 May 27;(99):e52753. doi: 10.3791/52753.

Analyzing the Functions of Mast Cells In Vivo Using 'Mast Cell Knock-in' Mice.

Gaudenzio N1, Sibilano R1, Starkl P1, Tsai M1, Galli SJ2, Reber LL3.

Thanks again! Gottfried

Yes, you are correct.  We have shown that mast cells down-regulate a variety of macrophage functions including tumor cell killing, superoxide and nitric oxide production.  In contrast, mast cells and histamine up-regulate LPS-induced inflammatory responses (IL-6 and COX2 expression) in endothelial cells in a synergistic fashion.

Thank you a lot. I will get hold of your articles and hope that I can come back to you if I need help to cite it correctly... in a "system" paper. Kind regards, Gottfried