CD4 and Allergy: For instance, in the context of allergy, eosinophil-derived IL-4 release during antigen presentation skews CD4 T cells toward the Th2 phenotype.117,118 After vaccination, it is possible that eosinophils may aid in the skewing of host responses toward type 2 due to secreting IL-4 and polarizing CD4 T cells toward Th2, similar to what was seen in allergy.