CD22 and pneumococcal infection: In order to use the same model in which IRA B cells were first detected, CD22-/- and C57BL/6 control mice were intranasally infected with E. coli. Similar to pneumococcal infections, intranasal infection with E. coli resulted in a significantly higher mortality (p<0.001) and higher CFUs in CD22-/- mice (p<0.001) (Fig 8A and 8B).