Molecular analysis of spontaneous nephrotropic anti-laminin antibodies in an autoimmune MRL-lpr/lpr mouse
Foster, M.H.; Sabbaga, J.; Line, S.R.; Thompson, K.S.; Barrett, K.J.; Madaio, M.P.
Journal of Immunology 151(2): 814-824
1993
ISSN/ISBN: 0022-1767 PMID: 8335911 Document Number: 421587
To explore the genetic relationship between anti-laminin and anti-DNA autoantibodies (autoAb), V-H gene and gene family expression were determined among autoAb derived from an individual 6-mo-old MRL-lpr/lpr mouse. Whereas 85% of the anti-DNA Ig were identified by one of two VH family probes, 7183 and V-HJ558, none of the anti-laminin antibodies (Ab) examined were recognized by these probes. Subsequent V region sequence analysis of three of the anti-laminin Ab revealed that they in fact utilized a J558 V-H gene (V-H50). Furthermore, FR2 and CDR2 oligonucleotide probes complementary to V-H50 recognized multiple anti-laminin Ab by Northern blot analysis; the FR2 probe recognized two control anti-DNA Ab, but neither probe recognized anti-DNA Ab from the same mouse. Polymerase chain reaction amplification of MRL-lpr/lpr genomic liver DNA using primers generated from V-H50 and V-k50 sequences indicated that all three anti-laminin Ig have a single replacement mutation in both their V-H and V-k genes. Search of the nucleic acid databases revealed that both germline V-H and V-k genes are expressed unmutated by murine lupus anti-dsDNA autoAb, previously sequenced in other laboratories. Sequence comparisons suggest that differences in anti-DNA and anti-laminin reactivity may be dependent upon somatically generated differences in the CDR3 regions of the H and L chains. The results indicate that lupus anti-laminin Ab can arise from distinct B cell populations but express the same unmutated germline V region genes as lupus anti-dsDNA autoAb. They further raise the possibility that these distinct B cell populations may be activated and expanded either: independently, by distinct Ig receptor ligands such as the Ag, laminin and DNA; or simultaneously, by a common ligand such as an anti-Id recognizing a common V region epitope.