IL4 and asthma: Research indicates that administering 50,000 IU of vitamin D to asthma patients who have low levels of serum vitamin D (less than 20 ng/mL) enhances their steroid response by upregulating the expression of GR-α, the glucocorticoid receptor, and lowering blood levels of IL-17F and IL-4, two cytokines linked to asthma [50].