[Interaction of oligonucleotides with blood serum proteins]

The interaction of alkylating derivatives of deoxyribonucleotides whose 5'-terminal phosphate group contains a 4-[(N-2-chloroethyl-N-methyl)amino]benzylamine residue with serum proteins has been studied. Incubation of whole human sera with various concentrations of the alkylating derivative, p(T)16, resulted in affinity modification of several proteins, among which albumin as well as IgM and IgG were the most readily detectable ones. The type of dependence of the degree of modification of these proteins on oligonucleotide concentration suggests that the oligonucleotides display a higher affinity for IgM than for IgG and albumin. Binding of reactive oligomer derivatives to serum proteins was inhibited by polyanions of different oligomeric composition, two-chain DNA and heparin, the latter being the strongest inhibitor of the immunoglobulins. These data point to a role of nonspecific ion-to-ion interactions in the IgG-oligonucleotide complex formation. Oligonucleotide interaction with murine monoclonal antibodies GI was inhibited by a specific antigen which suggests that oligonucleotides may interact with immunoglobulin either at or near a site where the antigen is recognized by the antibody.