Influence of VH CDR3 arginine and light chain pairing on DNA reactivity of a bacterial DNA-induced anti-DNA antibody from a BALB/c mouse.

Anti-DNA induced in BALB/c mice by immunization with bacterial (Escherichia coli) DNA resemble spontaneous anti-DNA from lupus mice in V gene use and cross-reactivity with other nuclear Ags, but lack the high V(H) CDR3 arginine content seen in anti-DNA from lupus mice. Moreover, the induced anti-DNA bind bacterial and mammalian single-stranded (ss) DNA and bacterial double-stranded (ds) DNA, but do not bind mammalian dsDNA. This reactivity profile is in contrast to that of the spontaneously arising anti-DNA of lupus mice, among which mammalian dsDNA reactive Abs are prominent. In this study we demonstrate that the addition of arginine to V(H) CDR3 of an induced anti-DNA confers the mammalian dsDNA binding characteristic of anti-DNA from lupus mice. The ability to confer mammalian dsDNA binding is dependent on both the position of the arginine in V(H) CDR3 and the light chain with which the heavy chain is paired, suggesting the light chain plays a more substantial role in DNA binding by this Ab than has previously been reported for other anti-DNA. Our data support the argument that V(H) CDR3 arginines tend to confer antimammalian dsDNA reactivity, leading to censure of B cells expressing these Abs and provides an explanation for the absence of arginine-rich V(H) CDR3 in the bacterial DNA-induced response.