Long-term cultured mouse mast cells: Ultrastructure, histamine and leukotriene levels

Interleukin 3 (IL3), dependent cells were obtained from bone marrow (9/10 ex-periments) and spleen cells (4/5 experiments), but not from the thymus. These cclls were similar to mucosal mast cell toluidine blue staining and electron mi-croscopy. They had heterogenous metachromatic granules, and some had large scroll-like structures. They also contained histamine (200-800 ng/10⁶ cells) for the first 2-5 weeks, whose level diminished to less than 30 ng/10⁶ cells by 10 weeks of culture. They also generated leukotriene (LT) C₄/D₄ (10-40 ng/10⁶ cclls) and LTB₄ (2-5 ng/10⁶ cells) for over 100 days of culture. In one experi-ment, bone marrow-derived mast cells after 150 days of culture began to pro-duce an IL3-like substance and proliferated exponentially without exogenous IL3.