Class-switching from mu to gamma 3 or gamma 2b production at pre-B cell stage.

An Abelson virus-transformed murine pre-B cell line class-switched from mu to gamma 3 or gamma 2b at the pre-B stage during culture. A class-switch was mediated by the deletion mechanism of the intervening CH genes on the active chromosome. This study showed for the first time that class-switching at the pre-B cell stage was not always confined to gamma 2b production.