PTGDR2 and allergic disease: The finding that the expression of the Th2A-related marker CRTH2 and the Th17-related marker CCR6 is mutually exclusive, and that some patients manifest clinical allergy symptoms in the absence of peanut-specific CRTH2+CD27- T cells with a dominance of CCR6+CD27+ T cells, prompted the hypothesis of the existence of 2 different cellular and molecular signatures, or immunotypes, with different effector and homing potential, associated with food allergy (53).