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Anti-DNA B cells in MRL/lpr mice show altered differentiation and editing pattern.

Li Y, Li H, Ni D, Weigert M - J. Exp. Med. (2002)

Bottom Line: This transgene codes for a heavy chain that forms anti-double-stranded DNA (dsDNA) antibody when paired with most members of the endogenous Vkappa repertoire, but certain L chains, referred to as Vkappa editors, do not sustain dsDNA binding in combination with 3H9H/56R.In the nonautoimmune 3H9H/56R BALB/c, most B cells generated do not bind DNA because the transgene itself is edited or is associated with a Vkappa editor.Anti-dsDNA B cells use noneditor kappas but, in addition, most anti-dsDNA B cells have edited the heavy chain transgene. lambda1 B cells (without the coexpression of a kappa editor) are found and the kappa/lambda1 MZ population is absent.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.

ABSTRACT
We have studied the regulation of anti-DNA B cells in transgenic mice with a heavy chain transgene (3H9H/56R). This transgene codes for a heavy chain that forms anti-double-stranded DNA (dsDNA) antibody when paired with most members of the endogenous Vkappa repertoire, but certain L chains, referred to as Vkappa editors, do not sustain dsDNA binding in combination with 3H9H/56R. In the nonautoimmune 3H9H/56R BALB/c, most B cells generated do not bind DNA because the transgene itself is edited or is associated with a Vkappa editor. A minor population of B cells (30%) bind dsDNA and express the lambda1 light chain (known to sustain 3H9H/56R DNA binding). These 3H9/56R/lambda1 B cells coexpress a kappa editor, and we propose that the down-regulation of the anti-DNA BCR caused by the dual L chain expression may prevent activation of this kappa/lambda population. These kappa/lambda B cells are sequestered in the marginal zone. Here, we studied the influence of autoimmunity on expression and regulation of 3H9H/56R. In 3H9H/56R MRL/lpr mice, the expression of anti-dsDNA is vastly accelerated. Anti-dsDNA B cells use noneditor kappas but, in addition, most anti-dsDNA B cells have edited the heavy chain transgene. lambda1 B cells (without the coexpression of a kappa editor) are found and the kappa/lambda1 MZ population is absent. Our results suggest that improper editing and failure to sequester autoreactive B cells may contribute to the breakdown of tolerance in MRL/lpr mice.

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Heavy chain sequences of B cells that retain the H chain transgene. The nucleotide and deduced amino acid sequences of heavy chains from hybridomas that are transgene-positive are aligned with 3H9H/56R transgene sequence. Mutations in the IgG-secreting clones (5, 48, 57, and 69) are indicated. A silent mutation in the FWR2 of clone 57 is shown in lowercase letter.
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fig2: Heavy chain sequences of B cells that retain the H chain transgene. The nucleotide and deduced amino acid sequences of heavy chains from hybridomas that are transgene-positive are aligned with 3H9H/56R transgene sequence. Mutations in the IgG-secreting clones (5, 48, 57, and 69) are indicated. A silent mutation in the FWR2 of clone 57 is shown in lowercase letter.

Mentions: A property of Lupus-associated autoantibodies is somatic mutation. The pattern of mutations shows evidence for antigen selection and mutations in anti-DNAs have been shown to create and modify DNA binding (27). Given that these MRL/lpr mice inherit a relatively high affinity anti-DNA, whether they undergo mutation and whether anti-DNA activity is modified is relevant. We could address this question because certain 3H9H/56R antibodies are not edited. The IgM anti-DNAs have no mutations (This applies just to VH; we are not sure about the germline sequences of the L chains expressed in this strain). The IgG anti-DNAs have multiple mutations and the mutation pattern shows evidence for selection. 10/14 replacements occur in CDRs or other sites that contribute to DNA binding, and 5/10 mutants are to arginines or asparagines, which are residues that favor DNA binding (Fig. 2) . Clone 69 does not bind DNA even though it is associated with a κ chain that should sustain DNA binding (22). Lack of DNA binding might result from arginine 97 to serine mutation or the potentially negative effect of the mutation of the highly conserved tyrosine 93 to cysteine.


Anti-DNA B cells in MRL/lpr mice show altered differentiation and editing pattern.

Li Y, Li H, Ni D, Weigert M - J. Exp. Med. (2002)

Heavy chain sequences of B cells that retain the H chain transgene. The nucleotide and deduced amino acid sequences of heavy chains from hybridomas that are transgene-positive are aligned with 3H9H/56R transgene sequence. Mutations in the IgG-secreting clones (5, 48, 57, and 69) are indicated. A silent mutation in the FWR2 of clone 57 is shown in lowercase letter.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196070&req=5

fig2: Heavy chain sequences of B cells that retain the H chain transgene. The nucleotide and deduced amino acid sequences of heavy chains from hybridomas that are transgene-positive are aligned with 3H9H/56R transgene sequence. Mutations in the IgG-secreting clones (5, 48, 57, and 69) are indicated. A silent mutation in the FWR2 of clone 57 is shown in lowercase letter.
Mentions: A property of Lupus-associated autoantibodies is somatic mutation. The pattern of mutations shows evidence for antigen selection and mutations in anti-DNAs have been shown to create and modify DNA binding (27). Given that these MRL/lpr mice inherit a relatively high affinity anti-DNA, whether they undergo mutation and whether anti-DNA activity is modified is relevant. We could address this question because certain 3H9H/56R antibodies are not edited. The IgM anti-DNAs have no mutations (This applies just to VH; we are not sure about the germline sequences of the L chains expressed in this strain). The IgG anti-DNAs have multiple mutations and the mutation pattern shows evidence for selection. 10/14 replacements occur in CDRs or other sites that contribute to DNA binding, and 5/10 mutants are to arginines or asparagines, which are residues that favor DNA binding (Fig. 2) . Clone 69 does not bind DNA even though it is associated with a κ chain that should sustain DNA binding (22). Lack of DNA binding might result from arginine 97 to serine mutation or the potentially negative effect of the mutation of the highly conserved tyrosine 93 to cysteine.

Bottom Line: This transgene codes for a heavy chain that forms anti-double-stranded DNA (dsDNA) antibody when paired with most members of the endogenous Vkappa repertoire, but certain L chains, referred to as Vkappa editors, do not sustain dsDNA binding in combination with 3H9H/56R.In the nonautoimmune 3H9H/56R BALB/c, most B cells generated do not bind DNA because the transgene itself is edited or is associated with a Vkappa editor.Anti-dsDNA B cells use noneditor kappas but, in addition, most anti-dsDNA B cells have edited the heavy chain transgene. lambda1 B cells (without the coexpression of a kappa editor) are found and the kappa/lambda1 MZ population is absent.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.

ABSTRACT
We have studied the regulation of anti-DNA B cells in transgenic mice with a heavy chain transgene (3H9H/56R). This transgene codes for a heavy chain that forms anti-double-stranded DNA (dsDNA) antibody when paired with most members of the endogenous Vkappa repertoire, but certain L chains, referred to as Vkappa editors, do not sustain dsDNA binding in combination with 3H9H/56R. In the nonautoimmune 3H9H/56R BALB/c, most B cells generated do not bind DNA because the transgene itself is edited or is associated with a Vkappa editor. A minor population of B cells (30%) bind dsDNA and express the lambda1 light chain (known to sustain 3H9H/56R DNA binding). These 3H9/56R/lambda1 B cells coexpress a kappa editor, and we propose that the down-regulation of the anti-DNA BCR caused by the dual L chain expression may prevent activation of this kappa/lambda population. These kappa/lambda B cells are sequestered in the marginal zone. Here, we studied the influence of autoimmunity on expression and regulation of 3H9H/56R. In 3H9H/56R MRL/lpr mice, the expression of anti-dsDNA is vastly accelerated. Anti-dsDNA B cells use noneditor kappas but, in addition, most anti-dsDNA B cells have edited the heavy chain transgene. lambda1 B cells (without the coexpression of a kappa editor) are found and the kappa/lambda1 MZ population is absent. Our results suggest that improper editing and failure to sequester autoreactive B cells may contribute to the breakdown of tolerance in MRL/lpr mice.

Show MeSH
Related in: MedlinePlus