{'fraction_non_alphanumeric': 0.033102386451116246, 'fraction_numerical': 0.0, 'mean_word_length': 4.990783410138249, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Fibroblast-dependent differentiation/proliferation of mast cells.

Fibroblast-dependent differentiation and proliferation of mast cells were reviewed from the viewpoint of mast cell-deficient mutant animals. Mice of W/Wv, Sl/Sld or mi/mi genotype are deficient in mast cells. However, since T cell-dependent differentiation and proliferation of mast cells are intact in these mutant mice, mast cells do develop when bone marrow cells of these mutant mice were cultured in the presence of T cell-derived growth factors. Cultured mast cells (CMC) of W/Wv mice cannot receive the proliferative stimulus from fibroblasts whereas fibroblasts derived from Sl/Sld embryos cannot provide normal (+/+) CMC with the proliferative stimulus. The W locus encodes a tyrosine kinase receptor and the Sl locus the ligand for the receptor. Although +/+ CMC acquire the phenotype resembling connective tissue-type mast cells when cocultured with fibroblasts in medium containing T cell-derived growth factors, mi/mi CMC do not. We recently found a mast cell-deficient mutant of rats. Biological features of the mast cell-deficient rats were very similar to those of W/Wv mice. The mast cell-deficient mutant animals are invaluable tools for investigations of differentiation/proliferation and functions of mast cells.