The important role of TYK2 in immune-surveillance is also in line with findings in patients who carry mutated TYK2 alleles which lead to loss of TYK2, lowered TYK2 levels [46], or expression of kinase-inactive TYK2 [47,48,49], and that show primarily immunodeficiencies. The gene discussed is TYK2; the disease is immunodeficiency disease.