our results indicate that ( i ) the great majority of normal pre-b cells in both fetuses and adults expresses intracytoplasmic mu chains only , ( ii ) immunoglobulin light-chain synthesis may be initiated during a late stage in pre-b-cell development , and ( iii ) heavy-chain isotype switching at the pre-b-cell stage may not occur during normal b-cell development .
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the
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b-cell development