DELAYED‐TYPE HYPERSENSITIVITY AND UNRESPONSIVENESS TO NUCLEIC ACID ANTIGEN The Role of the Epitope Density and Crossreactivity between Nucleoside Coupled to Cell*

Here we describe a new model to elicit cellular immunity and induce unresponsiveness to nucleic acid antigens. Delayed-type hypersensitivity could be elicited by immunizing and challenging Balb/c mice with either guanosine-coupled spleen cells (G-SC) or adenosine-coupled spleen cells (A-SC) measured by footpad swellings. The epitope density was critical for immunization. This cellular reaction was specific to nucleosides, and crossimmunity was observed beween A-SC and G-SC. In addition, crossunresponsiveness was observed between these two nucleosides. In contrast, soluble carrier proteins coupled with either guanosine or adenosine did not induce crossreactive immunity or unresponsiveness. This emphasizes the dichotomy in both the mechanism and the specificity of unresponsiveness induced by the same ligand bound to two different self molecules (such as cell or igG). Finally, cellular immunity to nucleic acid antigens might be useful in ascertaining its involvement in experimental systemic lupus.