Colocalization of antigen-specific B and T cells within ectopic lymphoid tissue following immunization with exogenous...

Chronic inflammation promotes the formation of ectopic lymphoid tissue morphologically resembling secondary lymphoid tissues, though it is unclear whether this is a location where Ag-specific immune responses develop or merely a site of lymphocyte accumulation. Ectopic lymphoid tissue formation is associated with many humoral autoimmune diseases, including lupus induced by tetramethylpecadentane in mice. We examined whether an immune response to 4-hydroxy-3-nitrophenyl acetyl-keyhole limpet hemocyanin (NP-KLH) and NP-OVA develops within ectopic lymphoid tissue ("lipogranulomas") induced by tetramethylpecadentane in C57BL/6 mice. Following primary immunization, NP-specific B cells bearing V186.2 and related heavy chains as well as lambda-light chains accumulated within ectopic lymphoid tissue. The number of anti-NP-secreting B cells in the ectopic lymphoid tissue was greatly enhanced by immunization with NP-KLH. Remarkably, the H chain sequences isolated from individual lipogranulomas from these mice were diverse before immunization, whereas individual lipogranulomas from single immunized mice had unique oligo- or monoclonal populations of presumptive NP-specific B cells. H chain CDR sequences bore numerous replacement mutations, consistent with an Ag-driven and T cell-mediated response. In mice adoptively transferred with OT-II or DO11 T cells, there was a striking accumulation of OVA-specific T cells in lipogranulomas after s.c. immunization with NP-OVA. The selective colocalization of proliferating, Ag-specific T and B lymphocytes in lipogranulomas from tetramethylpecadentane-treated mice undergoing primary immunization implicates ectopic lymphoid tissue as a site where Ag-specific humoral immune responses can develop. This has implications for understanding the strong association of humoral autoimmunity with lymphoid neogenesis, which may be associated with deficient censoring of autoreactive cells.