Bacterial lysates activates B cell differentiation and IL-10 production via Toll-Like Receptor-2 recognition (VAC11P.1064)

Abstract

Bacterial lysates (BL) are used to improve immune response in patients with respiratory infections. BL are constituted by a mixture of bacterial antigens derived from different bacterial species; species included in these lysates are 14 different bacteria: S. pneumoniae, K. pneumoniae, B. catarrahalis, S. aureus, H. influenza, S. alpha, and beta, S. faecalis, S. epidermidis, B. pertussis, Proteus sp., Pseudomonas sp., E. coli, and C. pseudodiphteriae (BL-14) It has been suggested that BL activate innate response through TLR, however if BL-14 are able to induce B cell activation is not known and this was the aim of our study. Peripheral mononuclear blood cells (PBMC) were obtained from healthy donors and cultured with/without BL-14 (IPI ASAC Pharma) at different concentrations, after stimulation with BL-14, supernatant were collected and IL-2, IL-4, IL-6, IL-10, TNF, IFN-γ, and IL-17A (BD Biosciences), were measured with cytometric bead arrays. PBMC were harvested at 24, 48 and 72 h, labelled against anti- CD19, CD38, CD69 or TLR2 (BD Biosciences), and analysed by flow cytometry. We observed dose-dependent increased activation of CD19+. After 72 h we observed a diminished frequency of B cells precursors and expansion of transitional B cells, these cells were TLR2+ cells. A significant increased concentration of IL-10 and IL-6 was observed at 24h, and 48 h after BL-14 stimulation. BL induces expansion of transitional B cells and IL-10 production through TLR2 recognition