Does low urinary sIgA predispose to urinary tract infection?

Median urinary secretory IgA (sIgA) (ELISA technique in unprocessed urine) was 1.36 mg/liter (range, 0.29 to 2.31) in healthy female controls at various times of the menstrual cycle. It was significantly lower in women with urinary tract infection (UTI) without antibody-coated bacteria. Such decrease was found both in women with acute UTI episodes (median, 0.16; range, 0.06 to 1.71) and in asymptomatic nonbacteriuric women with a history of UTI (median, 0.52; range, 0.05 to 2.13). In the latter women, sIgA in nasal secretions tended to be low, but salivary sIgA was unchanged. Urinary sIgA was elevated significantly in individuals with nephrostomy and antibody-coated bacteria (14.4 mg/liter, range, 3.6 to 20). The study showed that locally synthesized sIgA immunoglobulins were low in the urine of individuals with recurrent UTI independent of the presence or absence of bacteriuria at the time of the study. UTI per se did not interfere with sIgA secretion as shown by high sIgA in patients with upper UTI. Low urinary sIgA may represent one factor predisposing to recurrent UTI.