TLR2 is expressed on activated T cells as a costimulatory receptor - PubMed (original) (raw)

TLR2 is expressed on activated T cells as a costimulatory receptor

Mousa Komai-Koma et al. Proc Natl Acad Sci U S A. 2004.

Abstract

Toll is the founder of a group of pattern recognition receptors that play a critical role in the innate immunity in Drosophila. At least 10 distinct Toll-like receptors (TLRs), recognizing pathogen-associated molecular patterns, have now been identified in humans. Most investigations on TLRs have focused on cells of the innate system. We report here that naïve human T cells expressed high levels of cell-surface TLR2 after activation by anti-T cell receptor antibody and IFN-alpha. Activated cells produced elevated levels of cytokines in response to the TLR2 ligand, bacterial lipopeptide. Furthermore, CD4(+)CD45RO(+) memory T cells from peripheral blood constitutively expressed TLR2 and produced IFN-gamma in response to bacterial lipopeptide, which also markedly enhanced the proliferation and IFN-gamma production by CD45RO(+) T cells in the presence of IL-2 or IL-15. Thus, TLR2 serves as a costimulatory receptor for antigen-specific T cell development and participates in the maintenance of T cell memory. This suggests that pathogens, via their pathogen-associated molecular patterns, may contribute directly to the perpetuation and activation of long-term T cell memory in both antigen-dependent and independent manner.

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Figures

Fig. 1.

Fig. 1.

Naïve CD4+ T cells activated with anti-CD3 antibody and IFN-α expressed cell-surface TLR2 and TLR4. (a) Naïve CD4+ T cells purified from cord blood were activated with anti-CD3 antibody and IFN-α and analyzed for TLR2, TLR4, and MD2 mRNA at various time points by real-time PCR. (b) Cells activated with anti-CD3 antibody and IFN-α, or culture medium alone (nonactivated), for 72 h were washed extensively and triple stained with αTLR4-FITC, αTLR2-FITC, αCD3-ApC, and αCD4-PE antibodies or control isotype-match IgG. Cells were analyzed by FACS. (c) Cells were double stained with αCD-PE and αTLR-FITC or αCD3-PE and αTLR-FITC and analyzed by fluorescent microscopy. Results are representative of three experiments.

Fig. 2.

Fig. 2.

BMLF1-specific CD8+ T cells were expanded in vitro and stained with the BMLF1/HLA-A*****0201 phycoerythrin-labeled tetramer (y axis) and FITC-labeled antibodies (x axis) directed to TLR4 (Top Right), TLR2 (Middle Right), and isotype control (Bottom Right). Of the CD8/tetramer double-positive cells, 7.5% were positive for TLR4, and 5.1% were positive for TLR2.

Fig. 3.

Fig. 3.

The TLR2 ligand (BLP) but not the TLR4 ligand (LPS) acts as a costimulatory molecule for the activation of CD4+ T cells. (a) CD4+ T cells were purified from cord blood and cultured with immobilized anti-CD3 and IFN-α in the presence of graded concentrations of LPS or BLP. T cell proliferation and cytokine production were determined at 72 h. Vertical bars represent SEM (n = 4) of three experiments. *, P < 0.05; **, P < 0.01 (vs. culture with anti-CD3 + IFN-α without BLP). (b) The costimulatory effect of BLP is blocked by anti-TLR2 antibody. Cord blood CD4+ T cells were cultured with immobilized anti-CD3 antibody + IFN-α with or without BLP (2 μg/ml). The enhancing effect of BLP was significantly blocked by the presence of an anti-TLR2 antibody (10 μg/ml) but not by an isotype-matched normal IgG2a (not shown). Results are representative of three experiments. *, P < 0.05 vs. column without BLP.

Fig. 4.

Fig. 4.

APC from WT mice failed to modify the lack of effect of BLP on CD4+ T cells from TLR2-/- mice. (a) CD4+ T cells from WT or TLR2-/- mice were cultured for 3 days with CD3+ cell-depleted APC from WT mice (T:APC, 10:1) in the presence of immobilized anti-CD3 antibody. CD4+ T cells were then harvested, purified, and recultured with anti-CD3 antibody for a further 3 days. Cell proliferation and IFN-γ production were then analyzed. (b and c) CD4+ T cells from WT or TLR2-/- mice were cultured for 3 days either alone (b) or with 5% APC from WT mice (c) in the presence of anti-CD3 antibody. Cell proliferation and IFN-γ production were then determined. Data are mean ± SEM (n = 3) from three experiments. *, P < 0.05; **, P < 0.01 (vs. figures of WT cells cultured without BLP).

Fig. 5.

Fig. 5.

Expression of TLR2 on naïve (CD45RA+, Left) and memory (CD45RO+, Right) peripheral blood CD4+ T cells. Flow cytometry was carried out on CD4+ T cells by using anti-CD45RO (PE), anti-CD45RA (PE), and anti-TLR2 (FITC) antibodies. (a) Cells were stained for TLR2 ex vivo; mIgG denotes murine IgG isotype control. (b) Anti-CD3 activation induced TLR2 expression on naïve cells. This was further enhanced by the presence of BLP. The constitutively expressed TLR2 by memory cells was not significantly increased further by anti-CD3 and BLP stimulation. (c) TLR2 expression paralleled HLA-DR expression on these cells. Results are representative of three donors.

Fig. 6.

Fig. 6.

BLP increases the proliferation and IFN-γ production by memory CD4+ T cells in response to anti-CD3 activation or IL-2 or IL-15 stimulation. (a) CD45RA+ and CD45RO+ T cells from peripheral blood were cultured with anti-CD3 antibody. Proliferation and IFN-γ production was determined. *, P < 0.05; **, P < 0.01 (vs. culture with immobilized anti-CD3 alone). (b) CD45RA+ or CD45RO+ cells were cultured with IL-2 or IL-15 in the presence or absence of BLP. *, P < 0.05; **, P < 0.01 (vs. cultures of respective cytokine).

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