Single cell analysis of B lymphocytes from Wegener's granulomatosis: B cell receptors display affinity maturation within the granulomatous lesions

Increased amounts of anti-neutrophil cytoplasm antibody (ANCA) directed against proteinase 3 (PR3) are a diagnostic and pathogenic hallmark of full-blown Wegener's granulomatosis (WG). Aggregates of B lymphocytes proximal to PR3⁺ cells as well as plasma cells have been described as substantial components of Wegener's granuloma and could participate in forming tertiary lymphoid structures, which might promote autoantibody formation. Our aim was a molecular analysis of single B cells in order to develop a methodological approach that allows examination of potential ANCA formation in the tissue. Single B cells from cryo-conserved endonasal biopsies of three WG patients were isolated, using laser-assisted microdissection. Subsequently, their immunoglobulin variable heavy (VH) and light (Vκ, Vλ) chain genes were analysed by single cell polymerase chain reaction and direct sequencing. Sixteen immunoglobulin VH-Vκ or VH-Vλ chain gene couples were characterized. Twelve of these immunoglobulin gene couples resembled memory B cells. Two offsprings of one B cell were detected, indicating clonal expansion. VH genes representing 39 single B cells of WG tissues displayed significantly more mutations when compared with VH genes from peripheral blood of a healthy donor. The findings confirm and extend our previous results, arguing for an initial selection and affinity maturation of B cells within Wegener's granuloma. Further, the methodology provides the initial basis for the recombinant generation of antibodies derived from tissue cells.