Molecular characterization of J558 genes encoding tight-skin mouse autoantibodies: identical heavy-chain variable genes code for antibodies with different specificities.

Abstract

Tight-skin mouse, a mutant strain with a single gene defect, develops cutaneous hyperplasia and specific autoantibodies, like humans affected by scleroderma. The autoantibodies produced in the tight-skin mouse are encoded primarily by heavy-chain variable (Vu) genes from the J558 family. To understand the genetic basis of production of autoantibodies, we have analyzed the structure of J558 genes encoding these autoantibodies. The results showed that J558 genes encoding these antibodies were not derived from a selected germ-line gene(s) or a single subfamily but were derived from genes belonging to diverse J558 subfamilies. However, two prototype VH genes representing two new subfamilies were found to be repeatedly expressed in their germline form in eight independent clones. Autoantibodies with distinct specificities appear to be generated by pairing of similar/identical VH genes with different V,, genes derived from the same or different families. Fourteen of 18 autoantibodies shared a conserved heptapeptide sequence motif, YNEKFKG, in the second complementarity-determining region of heavy chains. Usage of germ-line genes from diverse J558 sub s bearing a common motif to encode autoantibodies suggests a regulatory role for this motif. Thus, selection and expansion of the autoreactive B-cell repertoire in the tight-skin mouse appear to be VH-gene mediated. The frequency of N nucleotide addition at diversity-joining (D-JH) junctions was lower, whereas the frequency of usage of the DFL16 segment was higher. Finally, in contrast to normal and other autoimmune mouse strains, the frequencies of D-D fusions and D inversions were higher in tight-skin mouse total immunoglobulin as well as autoantibody repertoires.Antibody diversity is generated by somatic recombination of diverse germ-line gene segments coding for heavy and light chains of immunoglobulins. In addition, somatic mutation, insertion or deletion of nucleotides at V(D)J junctions, D-D fusion, D inversion, and gene conversion that occur during the recombination process contribute to antibody diversity (1)(2)(3)(4)

Molecular Identification of Pathogenetic IdLNF+1 Autoantibody Idiotypes Derived from the (NZB×SWR)F1 Model for Systemic Lupus Erythematosus

“…Indeed, syngeneic SNF 1 T cells proliferated significantly to peptides 54-66 and 62-73, both of which contained this motif, supporting a potential role for this region of 540 H-CDR2 in the pathogenesis of SNF 1 nephritis. The KFKGK motif has been found in a large number of pathogenetic autoantibodies [58][59][60][61][62][63], despite its presence in only a small percentage of total heavy and light chain sequences [64]. Further, the ability of peptides containing this motif to stimulate SNF 1 T cells as well as B/WF 1 T cells is intriguing, since peptides containing triple base motifs have been shown to bind MHC Class II I-E d molecules [21,22], which are expressed by both SNF 1 and B/WF 1 mice.…”

Demonstration of Autoimmunity in the Tight Skin-2 Mouse: A Model for Scleroderma

“…However, Tsk1/ϩ mice develop ANAs including antiScl70 Abs, which were detected in supernatants from hybridomas established from Tsk1/ϩ splenocytes (36). The majority of the autoantibodies which arose in Tsk1/ϩ mice were shown to share a conserved heptapeptide sequence motif, YNEKFKG, in their H chains (37) and B cell clones producing autoantibodies in both the Tsk1/ϩ mouse and in SSc patients have been shown to share an interspecies cross-reactive Id (38).…”

Functional Properties and Molecular Characteristics of Autoantibodies Associated with Tight Skin Syndromea

“… The usage of subfamilies resembles the pattern of V gene expression in the pre‐B cell repertoire 33 and there is no bias in the usage of any V H J558 subfamilies in TSK autoantibodies 34 . Two new germline genes that may represent the prototypes for a new subfamily of V H J558 genes are repeatedly used in TSK autoantibodies.…”

“…The frequency of insertion of N nucleotides at D‐J H junctions is rare, whereas the frequency of D‐D fusions and D‐inversions is higher in both autoantibodies and the V H J558 repertoire of TSK mice. The molecular characteristics of TSK autoantibodies 32,34 are summarized in T 2. In summary, our results suggest that the establishment of the autoimmune repertoire in TSK mice is mediated by V H gene‐dependent selection of conventional B cells.…”