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  • Title: Toll-like receptor stimulation as a third signal required for activation of human naive B cells.
    Author: Ruprecht CR, Lanzavecchia A.
    Journal: Eur J Immunol; 2006 Apr; 36(4):810-6. PubMed ID: 16541472.
    Abstract:
    According to the current model, naive B cell activation is dependent on the sequential integration of two signals: B cell receptor (BCR) cross-linking by antigen, followed by cognate interaction with helper T cells through an immunological synapse. Using an improved method to purify human naive B cells we found that BCR stimulation and T cell help induced initial cell division but were not sufficient to promote survival and differentiation thus leading to abortive proliferation of naive B cells. Extensive B cell proliferation, isotypic switch and differentiation to immunoglobulin (Ig)-secreting cells was induced by addition of microbial products that trigger any of the Toll-like receptors (TLR) that are up-regulated in naive B cells upon BCR triggering. TLR agonists acted directly on B cells and were required irrespective of the nature of the T helper cells present. Supernatants of dendritic cells (DC) stimulated by DC-specific TLR agonists were also capable of enhancing B cell responses although to a much lower and variable extent. These results indicate that human naive B cell activation is critically dependent on innate stimuli acting optimally on TLR expressed by B cells. The coupling of BCR stimulation to TLR expression endows the human system with a high degree of specificity since it allows focusing of innate signals only on antigen-stimulated B cells.
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