IL-4 is produced by activated Th2 cells, activated NK cells, mast cells, and basophils, and causes selective differentiation of Th2 cells.[43] In a dose-escalation study (0.5 to 5mg/kg is given by subcutaneous injection thrice a week) IL-4 has been shown to cause improvement in psoriasis by inducing Th2 differentiation in human CD4+ T cells.[44]. Here, IL4 is linked to psoriasis.