Early on, at 24 hours of infection, reinforced expression of Btk in B cells provided some protection against S. pneumoniae growth, although CFU’s in lung and spleen of Cd19-Btk+ mice were not significantly reduced as compared to Btk-/- mice; however, at 48 hours the pneumococcal infection had dramatically, and equally, progressed in lungs, blood and spleen of both Btk-/- and Cd19-Btk+ mice (p<0.001 versus WT). Here, CD19 is linked to infection.