Keywords: CD4 + T cell CXCL8 IFN-γ IL-1 TCR TLRAdditional supporting information may be found in the online version of this article at the publisher's web-site
IntroductionThe immune system provides immediate and long-lasting defence against microbial pathogens by engaging distinct cell types. Cells of the innate immune system including macrophages, neutrophils and dendritic cells recognize conserved pathogen-associated molecular patterns (PAMPs) through germ line encoded patternrecognition receptors (PRRs) including Toll-like receptors (TLRs), Nod-like receptors (NLRs), retinoic acid-inducible gene 1 (RIG-1) like receptors and lectins [1]. Fig. 1 A) and mean CXCL8-fold increase over unstimulated was calculated. Data are shown as mean ± SEM of the five donors, and subjected to statistical analysis by Mann-Whitney test. (C) CD4 + T cells, naïve or TCR-preactivated for 24 h were stimulated with Pam3CSK4 for different time points and mRNA levels of CXCL8, CCL2, CCL3, CCL4, and CCL20 were checked by real-time PCR. Data are shown as mean ± SD of triplicate samples from two different donors. (D) Jurkat cells, naïve or activated with plate-bound anti-CD3 antibody and soluble anti-CD28 antibody for different time points were stimulated with flagellin for 16-20 h, after which CXCL8 was analyzed in the supernatants by ELISA. Percent CXCL8 in response to flagellin after different times of preactivation through the TCR is also shown. Data are shown as mean ± SD of triplicate cultures, from one experiment representative of two independent experiments. (E) Jurkat cells were activated with plate-coated anti-CD3 antibody and soluble anti-CD28 antibody for 24 h. Cells were washed and stimulated with flagellin for different time points. Cell lysates were run in a 12% SDS-PAGE, transferred to a nitrocellulose membrane, and probed with antibodies against activated signaling intermediates. The blot was developed using ECL. p38 protein levels were determined as loading control. Data shown are representative of three independent experiments. (F) Freshly isolated and activated T cells were stimulated with Pam3CSK4 and different concentrations of IL-1β for 24 h, and CXCL8 was determined in the supernatants. Data are shown as mean ± SD of triplicate cultures, from two different donors. Statistical significance was determined using Student's t-test. *p < 0.05; **p < 0.01; ***p < 0.001; ns: not significant. . Recent studies have established that T cells also express TLRs, which are otherwise known to be a distinctive feature of innate immune cells [7][8][9][10][11][12][13]. These studies raise the possibility that T cells might also contribute directly to innate immunity. However, the nature of innate immune responses that might be generated from T cells and their regulation remain incompletely worked out. Several studies have shown that TLRs on T cells can costimulate cytokine responses triggered through the TCR [7][8][9][10][11][12][13]. Microbial TLR ligands have also been shown to activate T cells independent of TCR signals [9,13,14]....