SCV formation can be associated with reduced TLR2-activity.

<p><b>A,C and D:</b> HEK293 cells were transfected with or without TLR2 cDNA (100 ng/well in <b>A+D</b> or 200 ng/well in <b>C</b>) and stimulated with <i>S. aureus</i> strains for 18–20 hours. IL-8 secretion was quantified as indicator of TLR2 activation. All diagrams show the results obtained in three independent experiments given as mean values ± SD (standard deviation). <b>A:</b> Stimulation of HEK293 cells w/o pTLR2 with <i>S. aureus</i> SH1000 and its isogenic thymidine-auxotrophic mutant SCV SH1000 <i>ΔthyA</i>; *p(SH1000:<i>ΔthyA) = </i>0.049. <b>B:</b> Comparison of SpA expression in SH1000 (TLR2^high) and its isogenic SCV SH1000 <i>ΔthyA</i> (TLR2^low). Left: Western blot analysis of SpA expression in bacterial lysates using anti-SpA mAb and anti-murine IgG-HRP as secondary antibody. Right: Control blot incubated with human serum and biotinylated anti-human IgG+streptavidin-HRP. One representative experiment of n = 3 experiment is shown. <b>C:</b> HEK293 cells w/o TLR2 were stimulated with SA113 or its mutants <i>ΔhemB</i> and Δ<i>sdh</i> (grown on Mueller Hinton (MH) or Columbia agar (CA)) or with 1 µg/ml of the TLR2 ligand Pam₃CSK₄ (P3) or left unstimulated (<b>−</b>). <b>D:</b> Stimulation with five different clinical <i>S. aureus</i> SCV (isolate source: CF = cystic fibrosis, INV = invasive) and SA113. (<b>−</b>) = unstimulated.