IKBKB and immune system disorder: Furthermore, patients with homozygous null mutations of IKBKB exhibit less severe phenotypes than IKKβ-null mice [29,30]; whilst they go on to develop severe combined immunodeficiency, they are normal at birth and exhibit no liver damage or developmental defects seen in IKKβ-null mice, suggesting that IKKα can compensate within the canonical NF-κB pathway in human cells.