The cloning of normal “Mast” cells in tissue culture

Abstract A method is described for the cloning of normal mouse “mast” cells in tissue culture in a soft agar medium. The colonies contain cells in different stages of differentiation. It was shown that a colony can be initiated by a single colony forming unit, and that colonies are formed as a result of cell multiplication. Cell suspensions from adult spleen gave about 3 colonies per 10 5 cells seeded. A re‐cloning of these colonies gave about 3 colonies per 10 3 cells seeded. The frequency of colonies from SWR mice was higher with adult spleen than with adult thymus. No such colonies were obtained with adult lymph node cells. The formation of colonies was shown to require the presence of an embryo cell feeder layer. Since the feeder layers were seeded underneath the agar, the results indicate that the substance(s) required for the growth and differentiation of “mast” cells can pass through agar.