Polynucleotide antibody specificity

Antibodies specific for triple-helical polynucleotides clearly distin-... 

Plescia OJ, Braun W, Imperato S, Cora-Block E, Jaroskova L, Schimbor C (1968) Methylated serum albumin as a carrier for oligo- and polynucleotides. In Plescia OJ, Braun W (eds) Nuclei acids in immunology. Springer, New York Pressmann D, Goldberg AL (1968) The structural basis of antibody specificity. Benjamin, New York... 

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... 

The existence of conformational determinants has been clearly demonstrated through the use of synthetic polynucleotides in double-hehcal structures and in triple-stranded complexes. It has also been shown that the specificity of antibodies is determined by the macromolecular conformation of the immunogen. Thus single-stranded polynucleotides induce formation of antibodies specific for the single-strand, while double-stranded hehcal complexes of polynucleotides induce antibodies specific for these structures, and antibodies specific for triple-strand structures are induced by the triple-stranded polynucleotide complexes. 

In experimental studies on the formation of antibodies to a hapten-protein conjugate, it appears that the more immunogenic the protein, the better the response. Although proteins are usually the most efficient carriers, polypeptides, polysaccharides, lipid membranes, or even polynucleotides may be sufficient to impart im-munogenicity. In recent years, direct conjugation of simple chemicals to structural elements of cell membranes (especially of monocytes and macrophages) has been thought to play an important role in the induction of sensitization (de Weck 1975 Shearer 1975). The protein carrier or cell membrane structure of the host may contribute to the specificity of the response (partial autoimmunity). 

These results have clearly shown that, with the conditions of administration used, 3-butylazathioprine will enhance the antibody response of mice to sheep red blood cells. Similar non-specific enhancement has been obtained with chemically defined polynucleotides (Braun, Ishizuka, Yajimi, Webb Winchurch, 1971) and with the thiazoles tetramisole and levamisole (Renoux Renoux, 1972). Such compounds, together with a variety of chemically undefined preparations (Hiu, 1972), may augment natural surveillance against malignant cells. 

In order to elucidate the role of conformation of the immunogen, animals were immunized with complexes of polyribonucleotides (double- or triple-stranded) associated with MBS A. The antibodies obtained reacted specifically with double- or triple-stranded complexes and it was concluded that the specificity was determined by the macromolecular conformation of the immunogen (Nahon et al., 1967 Lacour et al., 1968 Michelson et al., 1971). Immunization of rabbits with DNA-MBSA or with double-stranded polynucleotide complexes adsorbed to MBS A ehcits antibodies belonging to the macroglobulin class (Stollar and Sandberg, 1966 Nahon-Merlin et al., 1973). 

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). 

Studies of the specificities of experimentally induced antipolynucleotide antibodies have yielded some information on the antigenic determinants which could exist in a molecule of nucleic acid. Like the antibodies to proteins or synthetic polypeptides, antibodies to polynucleotides can be directed against different antigenic determinants derived from sequential regions as well as conformational factors in the molecule. Since antibodies in which the specificity is associated with the heterocyclic bases are obtained by use of single-stranded polynucleotides or certain components of nucleic acids it is thus evident that the bases themselves can be included among the antigenic determinants of polynucleotides. 

Lacour, F., Michelson, A. M., Nahon, E. Specific antibodies to polynucleotide complexes and their reaction with nucleic acids importance of the secondary structure of the antigen. In Nucleic acids in immunology, ed. by Plescia O. J. and Braun W., p. 32-46. Berlin—Heidelberg—New York Springer 1968. 

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