Expression of Immunoglobulin Genes in Transgenic Mice and Transfected Cellsa

Abstract

Immunoglobulin (Ig) genes are expressed sequentially (first H-, then L-chain genes) during the development of B lymphocytes. These studies, performed with transgenic mice and transfected cells, were aimed at the regulation of turning on and off the rearrangement of Ig genes. The specific recombinase is active in pre-B cells, but not in plasma cells. Production of membrane mu, but not secreted mu or gamma-2b, turns off rearrangement of H genes. Feedback inhibition of kappa-gene rearrangement requires kappa and membrane mu. Kappa alone or in combination with secreted mu does not stop recombination. Mouse lambda genes were mapped by deletion analysis and pulsed-field gel electrophoresis. The gene order is V2-C2,4-V1-C3,C1. The distance between V2 and C2 is 74 kb, but that between V1 and C3, 1 is only 20 kb. V2 and C3, 1 are over 190 kb apart. Lambda genes appear to be rearranged in a subset of B cells that do not respond to feedback inhibition at the pre-B cell stage. Lambda and kappa genes are both rearranged and potentially functional in these cells. Kappa genes may then be deleted by recombination of a sequence (described by Selsing and Siminovitch et al.) downstream of C-kappa with sequences upstream of C-kappa. Presumably the recombinase is eventually inactivated in kappa-lambda cells by a mechanism that is different from H-kappa feedback.

Induction of tolerance to an IgG autoantibody.

“…There are few data relevant to allelic exclusion in y heavy chain transgenic mice. A lack of allelic exclusion has been reported in mice transgenic for a yl transgene (32) and generally in mice transgenic for a y2b transgene (33 (1992) the simultaneous production of protective and pathogenic antibodies may underlie the need for allelic exclusion.…”

The Protection: The Unit of Humoral Immunity Selected by Evolution

“…In contrast, Storb and coworkers (Ritchie et al 1984, Gollahon et al 1988, Hagman et al 1989 find it necessary to treat each of their findings with different light chain transgenics as independent, unrelated phenomena; each observation is interpreted by a unique mechanism. They characterize two types of transgenic, one K (Ritchie et al 1984, Gollahon et al 1988, the other Xj (Hagman et al 1989). Hybridomas from the K-transgenic (TGK) were analyzed for the rearrangement of endogenous (E) IgK (Ritchie et al 1984) and for the expression of both K and X (TGA:-|-E^.)…”

“…The only expected difTerences between given L-chain transgenics is quantitative and determined by the probability, on average, that complementation with an H-chain will effect the (LH)2-ST0P. In contrast, Storb and coworkers (Ritchie et al 1984, Gollahon et al 1988, Hagman et al 1989 find it necessary to treat each of their findings with different light chain transgenics as independent, unrelated phenomena; each observation is interpreted by a unique mechanism. They characterize two types of transgenic, one K (Ritchie et al 1984, Gollahon et al 1988, the other Xj (Hagman et al 1989).…”

“…Hybridomas from the K-transgenic (TGK) were analyzed for the rearrangement of endogenous (E) IgK (Ritchie et al 1984) and for the expression of both K and X (TGA:-|-E^.) in EX expressing cells (Gollahon et al 1988). The argument used by Ritchieet al (1984)foran(LH)2-STOPisbasedon the finding that, in hybridomas that secrete Ig containing the transgenic K, the endogenous Igsr-loci are not rearranged (i.e., >90%).…”

Light chain inclusion permits terminal B cell differentiation and does not necessarily result in autoreactivity

“…Whereas this rule seems to be quite effective in the case of the HC (4,5), it suffers remarkable exceptions at light chain (LC) loci. Indeed, several studies reported the presence of double-expressing ͞ B cells either at very low frequencies in normal mice or in human, and more abundantly in transgenic mice (6)(7)(8)(9) and plasmocytomas (10). Little is known about the mechanisms involved in the allelic exclusion of LC even if recent studies highlighted the importance of asymmetric demethylation of the locus (11,12) and feedback inhibition of the recombination machinery after the assembly and signaling by a non-self-reactive BCR (13)(14)(15)(16).…”