Although we did not evaluate either TFH cells that simultaneously express IL-4, IL-5 and IL-13, nor IgE affinity, we believe that the ability of leptin to increase the frequency of Fel d1-specific TFHIL- 21- able to produce Th2-related cytokines is one of the mechanisms that this adipokine uses to intensify cat allergy severity. This evidence concerns the gene IL4 and allergic disease.