The Ssta2 locus was mapped by intercrossing two mouse strains selected for high or low antibody response to flagellar antigens of Salmonella. The high producing mice were more susceptible to infection and showed reduced IFNγ levels in spleen homogenates, an observation that is consistent with the reduced IFNγ production in Ity3 susceptible mice during infection. The gene discussed is IFNG; the disease is infection.