It is not yet clear if these in vitro results reflect in vivo antimicrobial activity as the minimal inhibitory concentration of NPY to inhibit cell growth of Candida albicans is relatively high, 25 (56) or 240 mg/ml (197) NPY’s antimicrobial properties are also not universal; Staphylococcus aureus and Serratia marcescens, pathogenic bacteria linked to atopic dermatitis and elevated in the skin of individuals with primary immunodeficiency respectively, are both resistant to NPY (75, 197, 197, 199, 200). This evidence concerns the gene NPY and inborn error of immunity.