Nucleic acid-binding specificity and idiotypic expression of canine anti-DNA antibodies

Serum samples collected from eleven lupus dogs during an active phase of the disease all bound native and denatured DNA, poly(dT), poly(I) and poly(G). Nine bound poly(C); 10 bound poly(U); and 3 bound poly(A). Sera from 22 normal dogs were negative with all of these antigens. The canine sera were also probed for the presence of three idiotypic markers, one related to human lupus anti-DNA antibodies and two related to murine lupus antibodies. One canine lupus serum expressed idiotopes related to murine anti-DNA idiotype (Id) termed H130: (a) the canine serum bound to anti-H130 anti-Id; (b) it inhibited the binding of anti-H130 Id to its homologous Id; and (c) the anti-H130 Id inhibited the binding of the canine serum to DNA. These findings suggest that anti-DNA variable regions exhibit interspecies similarities, probably reflecting the conservation of the encoding gene segments through evolution.