Beschreibung:
<jats:p><jats:italic>Neisseria meningitidis</jats:italic> may cause severe invasive disease. The carriage state of the pathogen is common, and the reasons underlying why the infection becomes invasive are not fully understood. The aim of this study was to compare the differences between invasive and carrier strains in the activation of innate immunity. The monocyte expression of <jats:styled-content style="fixed-case">TLR</jats:styled-content>2, <jats:styled-content style="fixed-case">TLR</jats:styled-content>4, <jats:styled-content style="fixed-case">CD</jats:styled-content>14, and <jats:styled-content style="fixed-case">HLA</jats:styled-content>‐<jats:styled-content style="fixed-case">DR</jats:styled-content>, cytokine production, and the granulocyte oxidative burst were analyzed after <jats:italic>in vitro</jats:italic> stimulation by heat‐killed invasive (n = 14) and carrier (n = 9) strains of <jats:italic>N. meningitidis</jats:italic>. The expression of the cell surface markers in monocytes, the oxidative burst, and cytokine concentrations were measured using flow cytometry. Carrier strains stimulated a higher production of inflammatory cytokines and oxidative burst in granulocytes than invasive strains (all p < 0.001), whereas invasive strains significantly up‐regulated <jats:styled-content style="fixed-case">TLR</jats:styled-content>2, <jats:styled-content style="fixed-case">TLR</jats:styled-content>4 (p < 0.001), and <jats:styled-content style="fixed-case">CD</jats:styled-content>14 (p < 0.01) expression on monocytes. Conversely, the monocyte expression of <jats:styled-content style="fixed-case">HLA</jats:styled-content>‐<jats:styled-content style="fixed-case">DR</jats:styled-content> was higher after the stimulation by carrier strains (p < 0.05) in comparison to invasive strains. The <jats:styled-content style="fixed-case">LPS</jats:styled-content> inhibitor polymyxin B abolished the differences between the strains. Our findings indicate different immunostimulatory potencies of invasive strains of <jats:italic>N. meningitidis</jats:italic> compared with carrier strains.</jats:p>