Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Analysis of HLA B27 Effect On Macrophage Function Using Transgenic Mice

Inman,  R. D., Zhu,  F.

Purpose:

The association of HLA-B27 with spondyloarthritis remains the strongest genetic association in rheumatic diseases, but the mechanistic role of B27 in disease pathogenesis remains unresolved. Hypotheses of B27 mechanisms have implicated distinct features of cell physiology (such as an unfolded protein response) which would predict distinct functional features. The present study addressed this question in mice transgenic for class I MHC alleles.

Method:

Mice transgenic for HLA alleles B27, B7, and A2 were crossed with MHC class I-deficient mice (double knock-out, or DKO) so that the human HLA allele was the only class I MHC molecule expressed on the cell surface of the respective mice. Peritoneal macrophages were harvested after thioglycollate injection, and were coincubated with Salmonella typhimurium (1:10 cells/bacteria), IFN-g (100 units/ml), or LPS (10 mg/ml). Readouts included (i) phagocytosis of bacteria (ii) intracellular killing of bacteria (iii) nitrite generation (iv) TNF-a production (v) IL-10 production.

Results:

There was no significant difference in phagocytosis of S. typhimurium by macrophages of the respective mice at 1hr and 4hr time points. Intracellular killing of S. typhimurium was also comparable across the groups. There was no difference between the respective cells in nitrite generation after coincubation with S. typhimurium. In contrast, following exposure to S. typhimurium, B27+ macrophages produced less TNF-a (420.6- pg/ml +/- 16.6) than B7+ macrophages (630.4 pg/ml +/- 5.3) (p=0.002) but more than A2+ macrophages (302.5 pg/ml. +/- 20.5) (p=0.001). These B27-specific differences in TNF-a production were still observed when exogenous IFN-g was added to the cells concurrent with the bacteria. There was no HLA-related difference in TNF-a production after incubation with LPS. After incubation with Salmonella, B27+ macrophages produced more IL-10 (199.4 pg/ml +/- 7.1) than B7+ macrophages (123.6 pg/ml +/- 7.4) (p=0.003) or A2+ macrophages (98.4 pg/ml +/- 7.1) (p=0.002).

Conclusion:

Murine macrophages expressing HLA-B27 generate less TNF-a and more IL-10 than HLA-B7-positive macrophages after in vitro exposure to an arthritogenic pathogen. Diminished TNF-a production has previously been associated with defective host clearance of pathogens in vivo, suggesting that B27-related alterations in cytokine production may play a role in disease pathogenesis.

To cite this abstract, please use the following information:
Inman, R. D., Zhu, F.; Analysis of HLA B27 Effect On Macrophage Function Using Transgenic Mice [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1449
DOI: 10.1002/art.26523

Abstract Supplement

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