Double immunocytochemical staining for in vivo detection of epitope specificity and isotype of antibody-forming cells against synthetic peptides homologous to human immunodeficiency virus-1.

Many infections evoke a strong humoral immune response. Some (e.g., HIV-1, EBV, CMV) also lead to disorders of the B-cell system. Data concerning cell dysfunction are largely derived from in vitro studies, which necessarily exclude all microenvironmental influences. The aim of this study was to develop a tool for the investigation of epitope specific humoral immune responses in vivo. Mice were immunized with one of two synthetic peptides, both 21 amino acids long and homologous to regions of the HIV-1 gp160. Cryostat sections of spleen and lymph nodes were incubated with the corresponding peptide coupled to alkaline phosphatase and simultaneously incubated with peroxidase-conjugated rabbit antisera specific for mouse immunoglobulin isotypes. We were able to show simultaneous detection of epitope specificity, isotype, and localization of antibody-forming cells and immune complexes in tissue sections. It should prove useful for in vivo investigation of the development of specific (e.g., anti-HIV-1) humoral immune response, the determination of B-cell specificity in lymph node infiltrates, and the role of immune complexes in lymph node pathology.