Expression of Stat4 protein in mast cells. (A) Western blot analysis of cultured MMCs and cultured CTMCs. Cell lysates were blotted with anti-Stat4 (C-20) and anti–α-tubulin Abs. (B) Immunohistochemical analysis of tissue mast cells derived from the skin and stomach of B6^+/+ mice. Mast cells are identified as alcian blue–positive cells in the tissue. Anti–Stat4-reacted cells are indicated by arrowheads. Mucosal mast cells (asterisk) were not stained with anti-Stat4 Ab.