Aberrant Ig production by Sap-deficient B cells after in vitro activation. Small resting B cells from wild-type (○) and Sap-deficient mice (•) were stimulated for 6 days with LPS plus different cytokines as indicated. Each circle represents the concentration (μg/mL) of secreted Ig in the supernatant of the cells stimulated by the given culture condition. The average value of each isotype is indicated by a horizontal bar. Student t test, ^*P < .05.