Degranulation capacity of cultured mast cells in the presence of histamine releaser

Abstract

A PURE population of mast cells develops when suspensions of lymphoid cells prepared from mice pre-immunised with horse serum are grown on embryonic mouse skin fibroblast monolayers¹. These in vitro matured mast cells are capable of undergoing repeated cycles of degranulation and regeneration². Both IgG₁ antibody and the corresponding antigen and the compound 48/80 (ref. 3) trigger degranulation of more than 90% of the mast cells, releasing 80 to 90% of their histamine content². This produces an immediate effect on the cells in the fibroblast monolayer. The well-stretched cytoplasm is displaced, opening numerous ‘windows’ scattered over the whole monolayer². These capacities of cultured mast cells raise questions on the relationships between them, the degranulating agent and the degranulating products released into the medium. Using our tissue culture, mast cell behaviour can be studied in the continuous presence of the degranulating agent or of the degranulating products. We show here that mast cells regenerate degranulation irrespective of the continuous presence of the histamine releaser compound 48/80, but they become unresponsive to its degranulating effect, although they are totally degranulated by IgG₁ and the corresponding antigen.