Studies on the resistance to E. coli infection using chicks fed diet depleted (0 μg/kg), sufficient (0.85 μg/kg) or excess (1,000 mg/kg) in vitamin A (59), revealed that excess or insufficient vitamin A resulted in an increased susceptibility of chicks to E. coli infection accompanied by reduced immune response by impairing IgA and IgG production (68). The gene discussed is CD79A; the disease is escherichia coli infection.