Recognition via the class A scavenger receptor modulates cytokine secretion by human dendritic cells after contact with Neisseria meningitidis

Proinflammatory cytokines play a major role in the pathogenesis of meningococcal disease and their serum levels in patients are correlated with the outcome of infection. Dendritic cells initiate immunity against Neisseria meningitidis and are a major source of proinflammatory cytokines. Here we show that physical interaction of human DC with N. meningitidis via the class A scavenger receptor (SRA) modulates cytokine release by DC. Phagocytosis and uptake via SRA were shown to increase release of TNF-alpha, IL-1 beta and IL-6. In contrast, secretion of IL-8 is enhanced after recognition of N. meningitidis via SRA and not dependent on phagocytosis. Binding of N. meningitidis results in dephosphorylation of SRA but not in upregulation of SRA transcription. Unlike previously thought, not all meningococcal strains are recognized via SRA. A constitutively unencapsulated carriage isolate could be shown not to bind to SRA and induce proinflammatory cytokines independent of this receptor. In conclusion, recognition via SRA by dendritic cells is likely to play a central role in the immune response to N. meningitidis.