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Published September 19, 1980 | public
Journal Article

DNA Sequences Mediating Class Switching in α-Immunoglobulins


Immunoglobulin class switching involves specific DNA rearrangements of the gene segments coding for heavy chain constant regions (C_H) during B lymphocyte differentiation. In two different cases of C_µ to Cɑ switching examined here (T15 and M603) and one taken from the literature (MC101), three different sites on the 5' side of C_µ and three different sites on the 5' side of C_ɑ are joined together in the process of C_H switching. The sequences surrounding the three germ-line C_ɑ sites of recombination are highly conserved blocks of 30 nucleotides that may serve as recognition sequences for C_H switching to the C_ɑ gene. This putative recognition sequence is repeated 17 times in approximately 1400 nucleotides of the germ-line C_ɑ 5' flanking sequence. The lack of homology between this C_ɑ sequence and sequences reported for the C_(y1) and C_(y2b) switch sites suggests that heavy chain switching is mediated by class-specific recognition sequences and, presumably, class-specific regulatory mechanisms. In addition, it appears that in one example (MC101) C_H switching progressed from C_µ to C_ɑ to C_(y1). This switching pathway may present difficulties for the simple deletional model of C_H switching.

Additional Information

© 1980 American Association for the Advancement of Science. 8 July 1980; revised 1 August 1980. This research was supported by NSF grant PCM 76-81546, PHS grant AI 09072, and NIH training grant GM 07616. All experiments involving recombinant organisms were conducted in accordance with the NIH Guidelines on Recombinant DNA. We thank N. Kupperman for assistance with restriction mapping and S. Crews, D. Goldberg, and M. Kronenberg for helpful discussions.

Additional details

August 19, 2023
October 20, 2023