Anti-polynucleotide antibodies, specificity

The antisera thus precipitate a polynucleotide which is one of the components of the immunogen and also a heterologous polynucleotide. The fact that anti-poly I poly C precipitates poly I in single-stranded form suggests the possibility that the sera contain, in addition to antibodies specific for... 

In order to define the specificity of the antibodies and to attempt to identify the antigenic determinants (or groups of antigenic determinants) Nahon-Merlin et al. (1973 a) studied the cross-reactions of anti-poly I poly C antibodies with different polynucleotides and polynucleotide complexes by direct precipitation and by specific absorption of antibodies. The rabbits respond to immunization with poly I poly C — MBSA, with a production of antibodies which varies according to the rabbit the sera contain from 700 to 1000 [i.g/ml of antibodies. 

Analysis of the specific absorption of anti-poly I poly C antibodies by double-stranded polynucleotide complexes reinforces both the idea of specificity of these antibodies for double-stranded structures and also the immunochemical differences between the three double-helical complexes. Thus poly rA poly rU, poly dG poly dC and poly rG poly rC absorb, respectively, 81.5, 73.3 Sind 57.7% of the antibodies in the homologous system. In order to inhibit 50 % of the reaction with the homologous antigen, 5-7 [xg of poly A poly U, 12.5 xg poly dG poly dC, and 85 [xg of poly rG poly rC... 

The specificity of antibodies induced in mice by poly I poly C MBS A, or by poly I poly C in emulsion with complete Freund s adjuvant, or in the hamster by poly I poly C — MBS A, has been studied less extensively. While in sera to poly I poly C — MBS A of rabbits the presence of anti carrier protein antibodies has been detected easily, this is not true of the sera of mice immunized by the same immunogen, which react essentially with synthetic polynucleotides (Lacour et al., 1971). 

Poly G — MBSA, like poly A, poly I or poly C, induces antibodies in which the specificity is associated with the nature of the base. Nevertheless these anti-poly G antibodies do not react with nucleic acids whereas the other antibodies to single-stranded polynucleotides react with denatured DNA (Seaman et al., 1965). This could be due to partial renaturation especially... 

Immune sera against poly A poly U, anti-poly I poly C and anti-poly G were used as controls. Anti-poly G does not precipitate any of the RNAs tested, whereas antibodies to the two complementary complexes precipitate all the RNAs, regardless of origin or fraction (Table 7 to 9). Thus antipoly G poly C antibodies show a specificity for ribosomal RNA from animal cells, and for certain viral RNAs furthermore they distinguish between rRNA and tRNA. In contrast, antibodies obtained by immunization with other polynucleotide complexes such as poly A poly U and poly I poly C show no specificity for any RNA whatever its type or origin, with the exception however of double-stranded viral RNA (Stollar, 1970). 

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