Mucosal immune mechanisms are believed to be important in host defense against urinary tract infection. To study the human immune response in the urinary tract, peripheral blood antibody-secreting cells (ASC), believed to originate from the mucosal surfaces, were investigated with the enzyme-linked immunospot assay. Pathogen-specific ASC were found in 17 (89%) of 19 patients with pyelonephritis and in 12 (70%) of 17 with LUTI (lower urinary tract infection); for infections caused by Escherichia coli, the respective figures were 17 (100%) and 10 (71%). The responses in pyelonephritis were stronger (P < .001) and lasted longer than those in LUTI: 15 patients with pyelonephritis (74%) but only 1 with LUTI (6%) had > 100 ASC/10(6) cells. A similar difference was seen in the number of all immunoglobulin-secreting cells. The ASC assay offers a new means for assessing the human immune response in urinary tract infection and may be useful in localizing the infection. It might prove valuable in predicting harmful postinfection processes.

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