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PLoS One. 2010 Jan 20;5(1):e8808. doi: 10.1371/journal.pone.0008808.

MHC class II molecules enhance Toll-like receptor mediated innate immune responses.

Author information

  • 1Division of Immunology/Allergology, University of Zurich, Children's Hospital, Zurich, Switzerland. remo.frei@kispi.uzh.ch

Abstract

BACKGROUND:

Major histocompatibility complex (MHC) class II molecules play crucial roles in immune activation by presenting foreign peptides to antigen-specific T helper cells and thereby inducing adaptive immune responses. Although adaptive immunity is a highly effective defense system, it takes several days to become fully operational and needs to be triggered by danger-signals generated during the preceding innate immune response. Here we show that MHC class II molecules synergize with Toll-like receptor (TLR) 2 and TLR4 in inducing an innate immune response.

METHODOLOGY/PRINCIPAL FINDINGS:

We found that co-expression of MHC class II molecules and TLR2 or TLR4 in human embryonic kidney (HEK) cells 293 leads to enhanced production of the anti-microbial peptide human-beta-defensin (hBD) 2 after treatment with TLR2 stimulus bacterial lipoprotein (BLP) or TLR4 ligand lipopolysaccharide (LPS), respectively. Furthermore, we found that peritoneal macrophages of MHC class II knock-out mice show a decreased responsiveness to TLR2 and TLR4 stimuli compared to macrophages of wild-type mice. Finally, we show that MHC class II molecules are physically and functionally associated with TLR2 in lipid raft domains of the cell membrane.

CONCLUSIONS/SIGNIFICANCE:

These results demonstrate that MHC class II molecules are, in addition to their central role in adaptive immunity, also implicated in generating optimal innate immune responses.

[PubMed - indexed for MEDLINE]
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