Characterization of Somatically Mutated S107 VH 11-encoded Anti-DNA Autoantibodies Derived from Autoimrnune (NZB x NZW)F1 Mice By Samuel M . Behar, Daniel L . Lustgarten, Sylvie Corbet, and Matthew D. Scharff From the Department of Cell Biology and The Irvington House Institute, Albert Einstein College of Medicine, Bronx, New York 10461 Summary We have studied 19 5107 heavy chain variable region gene (V 11)-encoded monoclonal antibodies from NZBWF1 mice . These studies show that a single V gene can encode both antibodies to foreign antigens (anti-phosphorylcholine) and to self antigens (anti-double-stranded DNA) in the same animal . All of the anti-DNA antibodies contain many somatic mutations compared with the relevant germline genes . Since the anti-DNA antibodies were extensively somatically mutated and had undergone isotype switching, the response seems to be T cell dependent. While some of the antibodies appear to be the products ofan antigen-driven and antigen-selected response, a number of characteristics of the antibodies suggest that forces other than antigen are contributing to the stimulation and selection of this response. T he serum of patients with SLE contain IgG antibodies that bind strongly to double-stranded DNA (dsDNA) 1 (1) and contribute to the glomerulonephritis that is a major cause of death in this disease (2) . The potential for inves- tigating the origins of these antibodies is greatly facilitated by the availability of lupus-prone strains ofmice such as (NZB x NZW)F1 (NZBWFI) (3) . Before the onset of detectable pathology, NZBWF1 mice produce IgM antibodies that . react with DNA (4) . These antibodies are usually of relatively low affinity and their V region genes have not undergone significant somatic mutation (5, 6) . Since such antibodies are not as- sociated with major pathology, they are thought to be non- pathogenic. In contrast, older autoimmune mice that have developed proteinuria and pathological changes in their kidneys have IgG anti-dsDNA antibodies in their blood and at the sites of tissue damage (3) . An understanding of the molec- ular origins of these pathogenic autoantibodies could pro- vide some understanding of why autoimmune lupus-prone strains ofmice develop such antibodies . In particular, it would be useful to determine whether the germline genes that en- code autoantibodies in autoimmune animals are different from the homologous genes in nonautoimmune mice (7), whether the same germline genes also encode antibodies against envi- 'Abbreviations used in this paper. dsDNA, double stranded DNA ; FW, framework; (NZB x NZW)Fi, NZBWFI; PC, phosphorylcholine ; R, replacement ; S, silent; ss, single stranded DNA; V , heavy chain variable region gene, ronment and self antigens, and whether the autoantibodies are specifically elicited by foreign or self antigens or are the product of a general polyclonal activation of all B cells (8) . An experimental approach to these questions was suggested by our finding that a single amino acid substitution in the S107 antiphosphorylcholine antibody converted it from an antibody that protects mice from Streptococcus pneumoniae (9) to a potentially pathogenic anti-dsDNA antibody (10) . This in vitro paradigm seemed likely to be relevant to in vivo events since others had shown that S107-like anti-DNA antibodies were present in NZBWF1 and MRL/lpr mice (11, 12) . Since the V S107 germline family consists of only four highly ho- mologous members (13), we were able to clone and sequence all of the members of this family from both NZB and NZW mice (14, 15) . We also generated and sequenced five IgG anti- dsDNA antibodies encoded by the V,,Sl07 family from an autoimmune NZBWF1 mouse and showed that they were encoded by the V 11 member of the VH S107 germline family (14) . Here we report the sequences and DNA binding proper- ties of 14 additional antibodies from that same animal and three antibodies from another animal. These new sequences provide a better perspective of the V 11-encoded anti-DNA response. While the characteristics of some of these antibodies indicate that they are products of an antigen-driven and antigen-selected response, the sequences of others suggest that there are additional forces influencing the autoimmune re- sponse. 731 J. Exp . Med. ® The Rockefeller University Press - 0022-1007/91/03/0731/11 $2.00 Volume 173 March 1991 731-741 Downloaded from http://rupress.org/jem/article-pdf/173/3/731/1671671/731.pdf by guest on 13 December 2023