mast cell connective tissue type mast cell They are CD88-positive. The cytoplasmic granules contain high levels of histamine and heparin (mouse) or major neutral proteases, tryptase, chymase, carboxypeptidase A, and cathepsin G (humans). Reportedly, they cannot produce leukotrienes (LTC4) and IL-4. They are reportedly very heterogeneous depending upon location and can convert to the MC(T) phenotype. TC mast cells MC(TC) MCTC Mast cell subtype whose granules contain both the serine proteases tryptase and chymase. These cells are primarily found in connective tissue, such as the peritoneal cavity, skin, and intestinal submucosa. Their development is T-cell independent. connective tissue cell