CD89 is required for complement deposition, leukocyte infiltration, proteinuria, and hematuria. (A) Deposits of MBL and C3 detected by immunohistochemistry in frozen kidney sections of 12-wk-old α1KI-CD89Tg compared with α1KI and WT mice. (B) Immunostaining for the detection of CD11b⁺ infiltrates in frozen kidney sections of mice. (left) Representative sections. Arrows indicate CD11b⁺ cells. (right) Numbers of positive cells per glomerulus counted in 20 randomly chosen fields for each mouse at 200 magnification. n = 4 mice per group. Bars, 10 µm. (C and D) Protein to creatinine ratio measured in the urines of 12-wk-old α1KI-CD89Tg mice compared with WT and α1KI (C) and 3-, 6-, 12-, and 24-wk-old α1KI and α1KI-CD89Tg mice (D). 7–20 mice per group. (B and D) Error bars indicate SEM. (E and F) Ratio of albumin to creatinine (E) and hematuria (×10,000 red cells/ml; F) as measured in the urines of 12-wk-old WT, α1KI, and α1KI-CD89Tg mice. 7–14 mice per group. (G) Levels of creatinine in the serum of 12-wk-old α1KI and α1KI-CD89Tg mice. 23–25 mice per group. Bars represent the mean. *, P < 0.05; **, P < 0.01; and ***, P < 0.001 (using the nonparametric Mann-Whitney U test).