CPT1B and cystic fibrosis: However, their protease expression profile does not fit the distinct patterns of mucosal vs. connective tissue mast cells (e.g., Mcpt1 and Mcpt2 are regarded as a mucosal mast cell markers in mice, and Cpa3 is connective tissue mast cell marker, but all are expressed in the CF intestine; and whereas Cma1 is a connective tissue marker it is not expressed in the CF intestine) [38]–[41].