This Article Full Text Full Text (PDF) Other Versions of this Article: IAI.00100-07v1 76/2/477    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Muthukuru, M. Articles by Cutler, C. W. PubMed PubMed Citation Articles by Muthukuru, M. Articles by Cutler, C. W.

Antigen Capture of Porphyromonas gingivalis by Human Macrophages Is Enhanced but Killing and Antigen Presentation Are Reduced by Endotoxin Tolerance

Manoj Muthukuru and Christopher W. Cutler^*

Department of Periodontics and Implantology, School of Dental Medicine, Stony Brook University-SUNY, Stony Brook, New York 11794-8703

Received 18 January 2007/ Returned for modification 14 March 2007/ Accepted 29 October 2007

The innate and the adaptive arms of the mucosal immune system must be coordinated to facilitate the control of pathogenic invasion while maintaining immune homeostasis. Toll-like receptors, able to activate the cell to produce bactericidal and inflammatory cytokines but also able to upregulate antigen (Ag)-presenting and costimulatory molecules, are particularly important in this regard. We have previously shown that the chronically infected oral mucosa is in a state of endotoxin tolerance, as evidenced by the downregulation of Toll-like receptors 2 and 4 and of inflammatory cytokines and the upregulation of SH2-containing inositol phosphatase, an inhibitor of NF-B signaling. In the present study, we hypothesized that endotoxin tolerance would influence the ability of human macrophages to engage in Ag capture and killing of the oral pathogen Porphyromonas gingivalis and to upregulate costimulatory molecules and stimulate autologous T-cell proliferation. We show that uptake, but not killing, of P. gingivalis 381 is enhanced by endotoxin tolerance. Reduced killing is possibly due to a reduction of the intracellular lysosomes. We further show that the expression of the Ag-presenting molecule HLA-DR and costimulatory molecules CD40 and CD86 is dampened by endotoxin tolerance to the constitutive level. This, along with our previous evidence for reduction in immunostimulatory cytokines, is consistent with the observed decrease in the induction of autologous CD4⁺ T-cell proliferation by endotoxin-tolerized macrophages. Overall, these studies suggest that endotoxin tolerance, as observed in the inflamed oral mucosa, potentiates the innate Ag capture activity of macrophages but diminishes the potential of human macrophages to initiate the adaptive immune response. In conclusion, endotoxin tolerance, while helpful in bacterial clearance and in surmounting excessive inflammatory tissue damage, could potentially reduce the (protective) adaptive immune response during chronic infections such as periodontitis.

Published ahead of print on 12 November 2007.

Editor: J. L. Flynn

Present address: Department of Oral Medicine, Infection & Immunity, Harvard School of Dental Medicine, Boston, MA.