Rheumatology Advance Access published online on September 30, 2009
Rheumatology, doi:10.1093/rheumatology/kep289
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Impaired C3b/iC3b deposition on Streptococcus pneumoniae in serum from patients with systemic lupus erythematosus
1Department of Medicine, Centre for Rheumatology, University College London Hospital and 2Department of Medicine, Centre for Respiratory Research, Royal Free and University College London Medical School, Rayne Institute, London, UK.
Correspondence to:
Fiona Goldblatt, Centre for Rheumatology, Department of Medicine, University College London Hospital, 3rd Floor The Windeyer Building, 46 Cleveland Street, London W1T 4JF, UK. E-mail: fgoldblatt{at}ntlworld.com
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Abstract |
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Objective. To determine whether opsonization of Streptococcus pneumoniae with C3b/iC3b is impaired in serum from patients with SLE.
Methods. The ability of serum samples from 30 patients with SLE, 20 with non-SLE rheumatic diseases (RA, PsA, AS, SS) and 20 healthy controls to opsonize S. pneumoniae (strains D39 and Io11697) with C3b/iC3b was assessed using a standardized FACS technique and a FACSCalibur flow cytometer. Results were compared among the three groups using analysis of variance, followed by pairwise comparisons among groups using the Mann–Whitney U-test.
Results. The proportion of bacteria positive for C3b/iC3b was significantly lower in serum from patients with SLE (strain D39: 60.3% ± S.E.M. 2.87, strain Io11697: 55.3% ± 3.8) compared with healthy controls (strain D39: 70.6% ± 2.0, P = 0.01; strain Io11697: 67.8% ± 2.6; P = 0.05) and non-SLE rheumatic controls (strain D39: 69.8% ± 3.1; P = 0.03). For the patients with SLE, there was no association between C3b/iC3b deposition and serum complement levels or measurable classical pathway activity. C3b/iC3b deposition on S. pneumoniae was significantly lower in serum from SLE patients with a past history of pneumonia (n = 3) compared with those without (n = 27; P = 0.03).
Conclusions. Opsonization of S. pneumoniae with C3b/iC3b was significantly reduced in serum from patients with SLE compared with non-SLE rheumatic disease and healthy controls. Failure to appropriately activate the immune system via complement may contribute to the increased susceptibility of SLE subjects to infections, and may correlate with a risk of pneumonia in a subgroup of SLE patients.
KEY WORDS: Systemic lupus erythematosus, Infection, Opsonization, C3, S. pneumoniae
Submitted 26 March 2009;
revised version accepted 6 August 2009.
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