All Phenotypes Vpreb1b<tm1Ilm> MGI Mouse

immune system phenotype ( J:67609 )

N	• heavy chain allelic exclusion still occurs normally • IgM levels are normal

abnormal B cell differentiation ( J:67609 )

• B220+ cells decreased to about half of control levels in bone marrow

• CD19+ cells reduced in numbers in bone marrow

• B220+ CD19- cell numbers are normal in bone marrow

abnormal immature B cell morphology ( J:67609 )

• number of IgM+ cells reduced 25 fold in young and 10 fold in old mice

• transformation from pre-BII to immature B cells is normal

decreased mature B cell number ( J:67609 )

• IgM+ cells reduced 25 fold in young and 10 fold in older mice

• similar reduction in IgM+ IgD+ mature B cells

decreased B-1a cell number ( J:67609 )

• numbers are reduced in 10-12 day old mice

• numbers return to normal by 9-13 weeks of age

• only B cell lineage to recover to normal numbers

decreased pre-B cell number ( J:67609 )

• pre-BII cells reduced about 40 fold in young mice (B220+ CD25+)

• pre-BII cells reduced about 10 fold in older mice

• ratio of large to small pre-BII cells is about 1:1 or 1:1.5 compared to 1:4 in controls

• 5 fold reduction in large and 15 fold reduction in small pre-BII cells

• defective proliferative expansion of pre-BII cells

• decreased large pre-BII cells with further reduction of small pre-BII cells

increased pre-B cell number ( J:67609 )

• pre-BI cell numbers are increased about 2 fold in bone marrow (B220+, c-Kit+)

• CD19+, c-Kit+ cells also increased about 2 fold

abnormal splenic cell ratio ( J:67609 )

• total nucleated cells reduced to about 70% in young and 45% in older mice

• B cell numbers increase with age, mostly as mature cells

decreased IgG level ( J:67609 )

• slightly decrease IgG antibody response