Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


The Presence of Renal Platelet Microthrombosis in Patients with Lupus Nephritis Correlates with the Degree of Macrophagic Infiltration.

Gonzalo4,  Elena, Martinez-Vidal2,  María Paz, Santiago4,  Begoña, Redondo4,  Natalia, Loza1,  Estibaliz, Pablos3,  José Luis, Galindo3,  María

Fundación Española de Reumatología, Sociedad Española de Reumatología, Madrid, Spain
Servicio de Reumatología, Hospital 12 de Octubre, Madrid, Madrid, Spain
Unidad de Investigación y Servicio de Reumatología, Hospital 12 de Octubre, Madrid, Madrid, Spain
Unidad de Investigación, Hospital 12 de Octubre, Madrid, Madrid, Spain

Introduction:

Intravascular CD61+ platelet microthrombi are found in the kidney of patients with lupus nephritis independently of the presence of antiphospholipid antibodies. Our objective was to analyze the correlation between CD61+ intravascular platelet microthrombi and intra or extraglomerular CD68+ macrophagic infiltration degree as a marker of active inflammation.

Methods:

Seventy-two kidney biopsies from systemic lupus erythematosus (SLE) patients were immunohistochemically stained with CD68 (macrophage) and CD61 (platelet glycoprotein-IIIa). Intra or extraglomerular macrophagic infiltration was quantified using the image-processing program Image J. CD61+ microthrombi were identified as percentage of stained cells. Clinical data were retrospectively collected at the time of kidney biopsies, and during the follow-up for a mean time of 7.5 years after biopsies and were correlated to the immunohistochemical findings. The associations between categorical variables were tested using the chi-square or Fisher's exact test, where appropriate. The odds ratios with the corresponding 95% CIs were calculated. For continuous variables, the comparisons were carried out using the t-test for two independent samples. P-values <0.05 were considered significant.

Results:

most of SLE kidneys showed glomerular (94%) and extraglomerular (87%) macrophagic infiltration. Both glomerular and extraglomerular CD68+ macrophagic infiltration were higher in patients with proliferative (WHO subtypes III and IV) nephritis (p=0.001). The CD68+ glomerular infiltration degree was increased in samples with CD61+ platelet aggregates (p=0.03), whereas CD68+ extraglomerular infiltration was higher in samples with histological thrombotic microangiopathy (p=0,02) and focal cortical atrophy (p=0.02). The CD68+ glomerular infiltration grade was also higher in patients with positive a-dsDNA (p=0.009), hypocomplementemia (p=0.01), microhematuria (p=0.02), the presence of cellular casts in urine sediment (p=0.03), and was significantly associated with SLE activity index (SLEDAI) at the time of kidney biopsy (p=0.02). Preliminary results have shown a potential correlation between CD68+ macrophagic infiltration and higher levels of complement factor C4d expression (p=0.04). Patients with kidney failure at biopsy presented higher mean extraglomerular macrophagic infiltration (p=0.03). However, the presence of CD61+ platelet aggregates and density of CD68+ macrophagic infiltration were not associated with response to treatment, renal function evolution or nephritis relapse rate.

Conclusions:

In lupus proliferative nephritis, intra and extraglomerular macrophagic infiltration degree correlates with acute impairment of kidney function. Presence of acute microthrombi provides a good correlation with cellular infiltration grade. However, none of these parameters is a good prognostic marker of the renal function evolution or response to treatment. Further studies are needed to better define correlation between the presence of renal thrombosis and inflammatory cells infiltration and activation of complement system in patients with lupus nephritis.

To cite this abstract, please use the following information:
Gonzalo, Elena, Martinez-Vidal, María Paz, Santiago, Begoña, Redondo, Natalia, Loza, Estibaliz, Pablos, José Luis, et al; The Presence of Renal Platelet Microthrombosis in Patients with Lupus Nephritis Correlates with the Degree of Macrophagic Infiltration. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :482
DOI: 10.1002/art.28251

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