T cells and in situ cryoglobulin deposition in the pathogenesis of lupus nephritis

Abstract

We discuss a 53-year-old woman with systemic lupus erythematosus who presented with vasculitis, hypocomplementemia and nephritis. Although her serum complement 4 (C4) levels were zero, she had four copies of C4 gene. Renal biopsy revealed membranoproliferative glomerulonephritis and the presence of cryoglobulins, detected by electron microscopy, and significant numbers of T cells in the interstitium. Cryoglobulins were considered responsible for the complete consumption of C4 in the serum the levels of which improved gradually after treatment. T cells in the kidney were found to express CD44 and phosphorylated ezrin/radixin/moiesin which explain why they homed to the kidney inappropriately. The contribution of cryoglobulins and T cells in the expression of kidney pathology is discussed.

Figure 1. Electron microscopy study

A. Two of the three glomeruli studied by electron microscopy were within normal limits, and showed no deposits (Original magnification 4000X). B. One of the three glomeruli studied by electron microscopy showed mesangial interposition and deposits with substructure (Original magnification 6000X). C. All of the deposits had the characteristic substructure of cryoglobulins. No amorphous granular electron dense deposits were noted. (Original magnification 15000X).

Figure 2. T cells form a dense infiltrate in the kidney

Frozen sections of the kidney biopsy were fixed with ice-cold acetone and incubated with mouse anti-human CD3 (1:100). After thorough washing, sections were incubated with goat anti-mouse IgG labeled with Texas Red (1:50). Finally, nuclei were stained by brief incubation with DAPI (4',6-diamidino-2-phenylindole; 0.5 μg/mL) (4). Slides were scanned in a Nikon Eclipse Ti confocal microscope; images were analyzed with EZ-C1 v. 3.6 software.

Figure 3. Kidney infiltrating T cells express CD44v3 and CD44v6

Sections were fixed and stained with mouse anti-human CD3 and either rabbit anti-human CD44v3 or rabbit anti-human CD44v6 (1:100). After thorough washing, sections were incubated with goat anti-mouse IgG labeled with Texas Red and goat anti-rabbit IgG labeled with Alexa Fluor 488 (1:50).

Figure 4. Phosphorylated ERM proteins are detectable in infiltrating T cells; FoxP3 is absent

Sections were fixed and stained with mouse anti-human CD3 and either rabbit anti-human pERM or rabbit anti-human FoxP3 (1:100). After thorough washing, sections were incubated with goat anti-mouse IgG labeled with Texas Red and goat anti-rabbit IgG labeled with Alexa Fluor 488 (1:50).