URINARY SECRETORY IMMUNOGLOBULIN-A AND FREE SECRETORY COMPONENT IN PYELONEPHRITIS

The immune defense mechanisms of mucosal surfaces involve secretory im munoglobulin A (slgA) antibodies and, to a lesser degree, other specif ic and nonspecific immune factors. These antibodies are dependent on a secretory component (SC) for their transmission through the epitheliu m. This SC is also secreted without 1g as free SC (FSC). The kidney do es produce these proteins; however, the ability of the lower urinary t ract to secrete them has not been shown. Thus, an upper urinary tract infection should produce more urinary sig and possibly more FSC than a lower tract infection. To demonstrate this, urine was obtained from n ormal controls (N = 33), cystitis patients (N = 22), and pyelonephriti s patients (N = 27). Monoclonal antibodies binding to specific conform ational epitopes were used in an enzyme-linked immunosorbent assay to detect the levels of slgA and FSC in these groups. Previous slgA measu rements have been hampered by lack of specificity of the capture antib ody. Urine creatinine was obtained to correct for the effect of diures is. A one-tailed Student's t-test for nonparametric populations was pe rformed to assess differences. The slgA levels in the normal and cysti tis groups were equivalent (1.4 mu g/mg/mL and 1.3 mu g/mg/mL, respect ively; P = 0.32). When these two groups were compared with the pyelone phritis group (24.1 mu g/mg/mL), a statistically significant differenc e was seen (P = 0.012 and P = 0.011, respectively), with no overlap. T here was a statistical difference in the levels of FSC in these same g roups, but a large degree of overlap. Urinary level of slgA as measure d by this monoclonal antibody is a sensitive test to differentiate pye lonephritis from cystitis, but FSC levels are not predictive. This may be due to differential secretion of slgA by upper and lower urinary t ract mucosa when exposed to infectious agents. (C) 1995 by the Nationa l Kidney Foundation, Inc.