A role for TLRs in Moraxella-superantigen induced polyclonal B cell activation.
A number of microorganisms are capable of binding immunoglobulins (Igs) in a manner, which excludes binding to conventional antigen binding sites. Interaction of such bacterial proteins with surface immunoglobulins leads to polyclonal activation of B-lymphocytes. A recent example is Moraxella catarrhalis that binds to B lymphocytes in an IgD-dependent manner and induces proliferation and differentiation of B lymphocytes leading to the production of unspecific Igs. The activation is mediated by Moraxella IgD binding protein (MID), which specifically binds to both soluble IgD and the IgD B cell receptor (BCR). Besides cross-linking the BCR, whole Moraxella and outer membrane vesicles (OMVs) engage Toll like receptors (TLRs) to further increase the response. TLR activation leads to initiation of signaling pathways, which evoke a proinflammatory response against the invading microbes. Polyclonal B cell activation has in general been implicated in various phenomenons that are detrimental for the host but beneficial for pathogens, for example, autoimmune manifestations and redirection of the immune system.
Medical Microbiology, Department of Laboratory Medicine Malmo, Skane University Hospital, Lund University, Malmo, Sweden.
Kalpana
K
Singh
Burcu
B
Bayrak
Kristian
K
Riesbeck
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D006801:Humans; D007072:Immunoglobulin D / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D001936:Moraxella catarrhalis / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D018089:Superantigens / Q000276:immunology*; D051193:Toll-Like Receptors / Q000276:immunology*; D000511:alpha-Macroglobulins
D000942:Antigens, Bacterial; D007072:Immunoglobulin D; D018089:Superantigens; D051193:Toll-Like Receptors; D000511:alpha-Macroglobulins; C032306:polyclonal B cell activator