Abstract

Human B cells and their expressed antibodies are crucial in conferring immune protection. Identifying pathogen-specific antibodies following infection is possible due to enhanced humoral immunity against well-described molecules on the pathogen surface. However, screening for cancer-reactive antibodies remains challenging since target antigens are often not identified a priori and the frequency of circulating B cells recognising cancer cells is likely very low. We investigated whether combined ex vivo culture of human B cells with three innate stimuli, interleukin-17 (IL-17), B cell activation factor (BAFF) and the toll like receptor 9 (TLR-9) agonist DNA motif CpG ODN 2006 (CpG), each known to activate B cells through different signalling pathways, promote cell activation, proliferation and antibody production. Combined IL-17+BAFF+CpG prolonged B cell survival and increased proliferation compared with single stimuli. IL-17+BAFF+CpG triggered higher IgG secretion, likely by activating differentiated, memory and class-switched CD19 +CD20 +CD27 +IgD - B cells. Regardless of anti-FOLR antibody seropositive status, IL-17+BAFF+CpG combined with a monovalent tumour-associated antigen (folate receptor alpha (FOLR)) led to secreted antibodies recognising the antigen and the antigen-expressing IGROV1 cancer cells. In a seropositive individual, FOLR stimulation favoured class-switched memory B cell precursors (CD27 -CD38 -IgD -), class-switched memory B cells and anti-FOLR antibody production, while IL-17+BAFF+CpG combined with FOLR, promoted class-switched memory B cell precursors and antibody-secreting (CD138+IgD-) plasma cells. Furthermore, IL-17+BAFF+CpG stimulation of peripheral blood B cells from patients with melanoma revealed tumour cell-reactive antibodies in culture supernatants. These findings suggest that innate signals stimulate B cell survival and antibody production and may help identify low-frequency antigen-reactive humoral responses.

Original languageEnglish
JournalClin Exp Immunol
Early online date5 Dec 2021
DOIs
Publication statusPublished - 5 Dec 2021

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