Tubular B7-1 expression parallels proteinuria levels, but not clinical outcomes in adult minimal change disease patients

Abstract

B7-1 is thought to play a pathogenic role in minimal-change disease (MCD). Recently, however, doubts have arisen regarding the role of B7-1 expression in MCD. Therefore, we aimed to identify the presence and clinical significance of B7-1 expression in MCD patients. The study participants included 28 adult MCD patients for whom kidney specimens were available. The intensity of B7-1 expression was assessed by two independent specialists. We analysed the association between the intensity of B7-1 expression and clinicopathological variables. No B7-1 expression in the glomeruli was observed in any of the 28 patients. Unexpectedly, however, 75.0% of the patients exhibited tubular B7-1 expression, with 35.7% demonstrating weak positive expressions and 39.3% demonstrating strong positive expressions. The level of proteinuria significantly increased as the intensity of tubular B7-1 expression increased. We also found trends of increasing blood urea nitrogen and serum creatinine levels with increased intensity of tubular B7-1 expression. However, we could not observe definite differences in long- and short-term clinical outcomes depending on the intensity of tubular B7-1 expression. In conclusion, B7-1 was expressed in renal tubular cells but not in glomeruli in adult MCD patients. The intensity of tubular B7-1 expression paralleled proteinuria levels, but not clinical outcomes.

Figure 1. Representative examples of B7-1 expression.

(A) Strong expression in tonsillar lymphocytes. (B) Negative staining in renal tubular epithelial cells and glomeruli. (C) Weak expression in renal tubular epithelial cells. (D) Strong expression in renal tubular epithelial cells (original magnification, ×200).

Figure 2. Kidney function and proteinuria according to the intensity of tubular B7-1 expression.

(A) Urinary protein-to-creatinine ratio. (B) Blood urea nitrogen. (C) Serum creatinine. Differences were analysed by using the Kruskal-Wallis test. *P < 0.1, **P = 0.033, and ***P = 0.004 by Mann-Whitney U test, compared with the tubular B7-1 expression-negative group.

Figure 3. Intensity of the tubular B7-1 expression and clinical outcomes.

CR, complete remission. Differences were analysed by using the chi-square test, and all clinical outcomes were not statistically significantly different in terms of the intensity of tubular B7-1 expression.