Comparative Nephritogenicity of Two Monoclonal Antibodies That Recognize Different Epitopes ofRat Thy-1.1 Molecule

Abstract

The pathophysiological role of the Thy-1.1 molecule expressed on rat mesangial cells with regard to mesangial cell dysfunction and injury remains unknown. The mechanism of Thy-1.1-associated injury has now been investigated with two monoclonal antibodies, 1-22-3 and OX7, that recognize different epitopes of Thy-1.1. Mesangiolysis and mesangial cell proliferation were more marked in rats injected with 1-22-3 than in those treated with OX7. Immunostaining for rat complement component C3 and also C9 was similar in the kidneys of rats 1 h after injection of either antibody. Alpha smooth muscle actin was first detected 3 days after injection of 1-22-3 and peaked on day 5; type I collagen staining showed a mesangial pattern on days 5 and 10. The staining for alpha smooth muscle actin and type I collagen was less intense in OX7-treated rats than in the 1-22-3-injected rats. The amounts of mRNAs encoding collagen types I and III peaked 5 days after injection of 1-22-3 and 10 days after injection of OX7. Rats injected with 1-22-3 developed proteinuria that was already marked on day 1 and peaked at 150 mg/day on day 3, whereas OX7 induced a low grade of proteinuria with large interindividual variability on day 3. Immunostaining for rat C3 in the normal rat kidneys, incubated in vitro with 1-22-3 or OX7 followed by incubation with normal rat fresh serum as a complement source, as well as the levels of serum complement activity, CH50, 30 min after injection of 1-22-3 or OX7 were similar, suggesting that the difference in the nephritogenicity of these two antibodies is not attributable to a difference in their complement-fixing activities, but rather may result from the difference in epitope specificities. The epitope recognized by 1-22-3 thus appears to be important in the initiation and progression of antibody-induced nephritis.

Exogenous 5′-nucleotidase improves glomerular autoregulation in Thy-1 nephritic rats

“…A mouse monoclonal antibody to rat Thy-1 antigen (mAb1-22-3; 2 mg) or control (2 mg murine IgG in 1 ml saline) was intravenously administered to the rats. We used mAb1-22-3 because our previous data demonstrated that it was more effective than OX-7 in inducing mesangiolysis (25). Two days later (29), the rats were anesthetized with pentobarbital sodium (50 mg/kg ip) and placed on a thermostatically controlled heated table to keep body temperature at 37°C, as detailed previously (24,38).…”

“…We are aware of no in vivo studies examining effects of a mono-clonal anti-Thy-1 antibody on renal autoregulation. In the present study, we assessed the role of mesangial cells in in vivo renal autoregulation, comparing controls and Thy-1 nephritis induced by mAb1-22-3, another monoclonal antibody against Thy-1, which recognizes a Thy-1 epitope different from OX-7, one that is more nephritogenic than OX-7 (25).…”

Decreased collagen-degrading activity could be a marker of prolonged mesangial matrix expansion

“…3 We have previously demonstrated that glomerular mRNA levels of type I and type IV collagens in a reversible model of mesangial matrix expansion increased on day 3, peaked on day 5 or 10, and then gradually decreased to normal levels. 4 Yagi et al 5 reported that glomerular mRNA levels of type I and type IV collagens increased on day 4, and then normalized by week 5 in a chronic model of GN. These findings indicate that impaired degradation, rather than the persistent synthesis of these collagens, is highly concerned with the development of chronic glomerular lesions.…”

Local Delivery of Angiotensin II Receptor Blockers into the Kidney Passively Attenuates Inflammatory Reactions during the Early Phases of Streptozotocin-Induced Diabetic Nephropathy through Inhibition of Calpain Activity

“…The primary antibodies were rabbit anti-rat Thy-1.1 [9] (a hybridoma producing OX-7 IgG1 that was purchased from the European Collection of Animal Cells, Porton Down, Salisbury, UK) for the identification of glomerular mesangial cells, mouse monoclonal anti-rat ED-1 (Serotec Ltd., Kindlington, UK) for the detection of infiltrating macrophages, biotinylated anti-CD31 (Serotec Ltd.) for the identification of endothelial cells, and mouse monoclonal anti-rat endothelial nitric oxide synthase (eNOS; Abcam, UK). Tetramethyl rhodamine B isothiocyanate-conjugated goat anti-rabbit IgG, and fluorescein isothiocyanate-conjugated rabbit anti-mouse IgG (Dako, Denmark) were used as secondary antibodies.…”