LOCAL IMMUNE RESPONSE IN UPPER URINARY TRACT INFECTION IN CHILDREN

Division of Infectious Diseases, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland; Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, Helsinki, Finland; National Public Health Institute, Turku, Finland; Department of Pediatrics, Turku University Central Hospital, Turku, Finland; Department of Medical Microbiology and Immunology, University of Turku, Finland

^* To whom correspondence should be addressed. Email: anu.kantele{at}hus.fi.

	Abstract

Vaccines are needed against urinary tract infections (UTI) in children, as episodes of pyelonephritis (PN) may cause renal scarring. Local immune mechanisms are regarded to confer protection, yet they have been poorly characterized in children. This study explores the local immune response in children by looking for newly activated pathogen-specific antibody-secreting cells (ASC) expected to be appearing transiently in the circulation as a response to UTI.

Urinary tract-originating ASC specific to each patient's own pathogen or P fimbria were studied in 37 children with PN. The children were examined for recidives and renal scarring in a six-month follow-up.

Pathogen-specific ASC were found in 33/37 children, the magnitude increasing with age. In contrast to adults with IgA-dominance, in 18/33 cases IgM dominated the response, more frequently in infants (63%) than in older children (30%). Most vigorous response was found to whole E.coli bacteria (geom. mean 63±2135 ASC/10⁶ PBMC), yet, responses were found to P fimbria (13±33 ASC/10⁶ PBMC), too. The response peaked at 1-2 weeks and was low/negligible after 3-7 weeks after the beginning of symptoms. Recidives were seen in seven and renal scarring in nine patients.

In conclusion, a response of circulating ASC was found in children with UTI, the magnitude increasing with age. As IgM is not present in urine, the IgM-dominance of the response suggests that systemic immune mechanisms are more important in the immune defense in children than in adults. In 81% of patients, no recidives were seen suggesting a successful immune defense.