Expression ofλand K Genes Can Occur in all B Cellsand is Initiated Around the Same Pre-B-CellDevelopmental Stage

摘要

Transgenic mice that carry a λ2 transgene under the control of the Vλ2 promoter and theEλ2-4 enhancer (λ2Eλ mice) are described. A high proportion of B cells in the spleen andthe bone marrow express the λ transgene on the cell membrane. λ2 protein is synthesizedby all λ2Eλ-derived spleen B-cell hybridomas that have retained the transgene, suggestingthat all B cells have the ability to express λ genes. Feedback inhibition of endogenous K-generearrangement is significant, but not complete. The results are similar to those withtransgenic mice expressing the same λ2 transgene under the control of the heavy-chainenhancer (λ2EH mice). Although the λ2EH transgene is expressed before the λ2Eλtransgene, feedback inhibition seems to occur at about the same stage of B-cell development,regardless of the timing of expression of the λ transgenes. Apparently, feedback is notnecessarily coincident with the assembly of a heavy-chain/light-chain complex in pre-Bcells. Expression of λ in the normal fetal liver coincides with the expression of K; thus, itappears that λ-gene transcription is not delayed. The differential rearrangement of K and λgenes is discussed in the light of these findings.