Urinary immunoglobulins in healthy individuals and children with acute pyelonephritis

Immunomodulation therapy offers new molecular strategies to treat UTI

Innovative solutions are needed for the treatment of bacterial infections, and a range of antibacterial molecules have been explored as alternatives to antibiotics. A different approach is to investigate the immune system of the host for new ways of making the antibacterial defence more efficient. However, the immune system has a dual role as protector and cause of disease: in addition to being protective, increasing evidence shows that innate immune responses can become excessive and cause acute symptoms and tissue pathology during infection. This role of innate immunity in disease suggests that the immune system should be targeted therapeutically, to inhibit over-reactivity. The ultimate goal is to develop therapies that selectively attenuate destructive immune response cascades, while augmenting the protective antimicrobial defence but such treatment options have remained underexplored, owing to the molecular proximity of the protective and destructive effects of the immune response. The concept of innate immunomodulation therapy has been developed successfully in urinary tract infections, based on detailed studies of innate immune activation and disease pathogenesis. Effective, disease-specific, immunomodulatory strategies have been developed by targeting specific immune response regulators including key transcription factors. In acute pyelonephritis, targeting interferon regulatory factor 7 using small interfering RNA or treatment with antimicrobial peptide cathelicidin was protective and, in acute cystitis, targeting overactive effector molecules such as IL-1β, MMP7, COX2, cAMP and the pain-sensing receptor NK1R has been successful in vivo. Furthermore, other UTI treatment strategies, such as inhibiting bacterial adhesion and vaccination, have also shown promise.

Hyperactivation of innate immunity is a disease determinant in urinary tract infections (UTIs). Modulation of innate immunity has promise as a therapy for UTIs. In this Review, the authors discuss potential mechanisms and immunomodulatory therapeutic strategies in UTIs.

Excessive innate immune responses to infection cause symptoms and pathology in acute pyelonephritis and acute cystitis.

Innate immunomodulation therapy is, therefore, a realistic option for treating these conditions.

Targeting excessive innate immune responses at the level of transcription has been successful in animal models.

Innate immunomodulation therapy reduces excessive inflammation and tissue pathology and accelerates bacterial clearance from infected kidneys and bladders in mice.

Innate immunomodulation therapy also accelerates the clearance of antibiotic-resistant bacterial strains.

The Multifaceted Nature of Immunoglobulin A and Its Complex Role in HIV

IgA is the most abundant immunoglobulin in mucosal secretions, and understanding the role of IgA in both protection from HIV acquisition and modulation of HIV disease progression is a field of considerable controversy and renewed research interest. Analysis of the RV144 clinical trial associated plasma HIV envelope-specific monomeric IgA from vaccines with reduced vaccine efficacy. The RV144 trial, however, only assessed for plasma IgA, which was not further subclassed, and the role of mucosal IgA was not addressed as mucosal samples were not collected. On the other hand, several studies have detected envelope-specific IgA in mucosal secretions of highly exposed persistently seronegative cohorts, while recent macaque simian-HIV passive immunization studies have suggested a potentially protective role for mucosal IgA. It is well established that total IgA in serum appears to correlate with HIV disease progression. In contrast, a selective deficit of anti-HIV IgA responses in HIV infection is apparent, with a number of recent studies beginning to elucidate the mechanisms behind these dysfunctional IgA responses. In this review, we highlight the dichotomy that exists in the literature as to whether anti-HIV IgA is protective or harmful to the host. Herein, we emphasize the importance of distinguishing between monomeric, multimeric, and isoforms of IgA and review what is known about the complex and diverse interactions of various molecular forms of IgA with HIV in both the systemic circulation and mucosal compartments.

Genetic risk for recurrent urinary tract infections in humans: a systematic review

Urinary tract infections (UTIs) are a frequent cause of morbidity in children and adults and affect up to 10% of children; its recurrence rate is estimated at 30–40%. UTI may occur in up to 50% of all women in their lifetimes and frequently require medication. Recent advances have suggested that a deregulation of candidate genes in humans may predispose patients to recurrent UTI. The identification of a genetic component of UTI recurrences will make it possible to diagnose at-risk adults and to predict genetic recurrences in their offspring. Six out of 14 genes investigated in humans may be associated with susceptibility to recurrent UTI in humans. In particular, the HSPA1B, CXCR1 & 2, TLR2, TLR4, TGF-β1 genes seem to be associated with an alteration of the host response to UTIs at various levels.

Global gene expression profiling of renal scarring in a rat model of pyelonephritis

Renal scarring is a serious complication of chronic pyelonephritis that occurs due to vesicoureteral reflux. In our study, we performed global expression profiling of the kidney during renal scarring formation in a rat pyelonephritis model. An inoculum of Escherichia coli was injected directly into the renal cortex. Histologically, renal scarring developed during the 3-to-4 week period after injection. The time-course expression profile of 18,442 genes was then analyzed using microarrays, followed by validation with real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Most of the genes found to be up-regulated during renal scarring are associated with immune and defense responses, including cytokines, chemokines and their receptors, complement factors, adhesion molecules and extracellular matrix proteins. These genes were up-regulated as early as 1 week after injection, when no fibrotic changes were yet evident, peaked at 2 weeks, and gradually decreased thereafter. However, a subset of cytokine genes was found to be persistently activated even at 6 weeks after injection, including interleukin (IL)-1beta, transforming growth factor (TGF)-beta, and IL-3. Further statistical analysis indicated that the pathways mediated by these cytokines are activated concomitantly with renal scarring formation. The products of these genes may thus potentially be novel non-invasive diagnostic or prognostic biomarkers of renal scarring.

Local immune response to upper urinary tract infections in children

Vaccines are needed against urinary tract infections (UTIs) 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 for children. This study explores the local immune response in children by looking for newly activated pathogen-specific antibody-secreting cells (ASC), expected to appear 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 recidivism and renal scarring in a 6-month follow-up study. Pathogen-specific ASC were found in 33/37 children, with the magnitude increasing with age. In contrast to the case for adults, with immunoglobulin A (IgA) dominance, in 18/33 cases IgM dominated the response, and this occurred more frequently in infants (63%) than in older children (30%). The most vigorous response was found to whole Escherichia coli bacteria (geometric mean, 63 +/- 2,135 ASC/10(6) peripheral blood mononuclear cells [PBMC]), yet responses were found to P fimbriae (13 +/- 33 ASC/10(6) PBMC), too. The response peaked at 1 to 2 weeks and was low/negligible 3 to 7 weeks after the beginning of symptoms. Recidivism was seen in seven patients, and renal scarring was seen in nine patients. In conclusion, a response of circulating ASC was found in children with UTIs, with the magnitude increasing with age. Since 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 recidivism was seen, suggesting a successful immune defense.

Humoral immune responses to the human immunodeficiency virus type-1 (HIV-1) in the genital tract compared to other mucosal sites

Infection with the human immunodeficiency virus-1 (HIV-1) must be considered as a primarily mucosal disease. On a worldwide basis, the absolute majority of HIV infections occur through mucosal surfaces of the genital and intestinal tracts, and the earliest and most dramatic immunologic alterations are induced by the virus in mucosal tissues. However, individual compartments of mucosal components of the immune system display remarkable differences with respect to dominant antibody isotypes, virus phenotypes, densities and origins of cells involved in innate and specific immunity, presence or absence of inductive sites, and routes of immunizations that induce humoral and cellular responses. In this regard, the mucosal immune system of the female and male genital tracts exhibit several features which are distinct from other mucosal tissues, including dominance of the IgG isotype, local as well as pronounced systemic origin of antibodies, the absence of organized lymphoepithelial inductive sites and limited humoral responses stimulated by local antigen administration. Furthermore, it is evident that, irrespective of the route of infection, HIV-1 induces easily detectable IgG but not IgA specific antibody responses. These differences must be considered in the design of protective vaccines against infection with HIV and other agents of sexually transmitted diseases.

Humoral immune responses to the human immunodeficiency virus type-1 (HIV-1) in the genital tract compared to other mucosal sites

Infection with the human immunodeficiency virus-1 (HIV-1) must be considered as a primarily mucosal disease. On a worldwide basis, the absolute majority of HIV infections occur through mucosal surfaces of the genital and intestinal tracts, and the earliest and most dramatic immunologic alterations are induced by the virus in mucosal tissues. However, individual compartments of mucosal components of the immune system display remarkable differences with respect to dominant antibody isotypes, virus phenotypes, densities and origins of cells involved in innate and specific immunity, presence or absence of inductive sites, and routes of immunizations that induce humoral and cellular responses. In this regard, the mucosal immune system of the female and male genital tracts exhibit several features which are distinct from other mucosal tissues, including dominance of the IgG isotype, local as well as pronounced systemic origin of antibodies, the absence of organized lymphoepithelial inductive sites and limited humoral responses stimulated by local antigen administration. Furthermore, it is evident that, irrespective of the route of infection, HIV-1 induces easily detectable IgG but not IgA specific antibody responses. These differences must be considered in the design of protective vaccines against infection with HIV and other agents of sexually transmitted diseases.

Mucosal immunoglobulins

Due to their vast surface area, the mucosal surfaces of the body represent a major site of potential attack by invading pathogens. The secretions that bathe mucosal surfaces contain significant levels of immunoglobulins (Igs), which play key roles in immune defense of these surfaces. IgA is the predominant antibody class in many external secretions and has many functional attributes, both direct and indirect, that serve to prevent infective agents such as bacteria and viruses from breaching the mucosal barrier. This review details current understanding of the structural and functional characteristics of IgA, including interaction with specific receptors (such as Fc(alpha)RI, Fc(alpha)/microR, and CD71) and presents examples of the means by which certain pathogens circumvent the protective properties of this important Ig.

Elevated levels of secretory immunoglobulin A (sIgA) in urinary tract infections

OBJECTIVE

Urinary secretory IgA (sIgA), an immunoglobulin synthesized locally in mucosal surface is an important immunological defense in preventing bacterial adherence to periurethral epithelia and uroepithelia. Therefore attempts were made to measure secretory IgA in the urine of children with urinary tract infections (UTI), by using sIgA specific ELISA.

METHODS

Fresh or unprocessed urine samples from healthy donors (children and adults N=10 each), 68 children and 17 Adults with UTI were tested for the presence of sIgA.

RESULTS

The level of sIgA in 10 healthy normal children was 2.7 +/- 0.94 ug/ml and that in 10 healthy adults was 5.2 +/- 0.73 ug/ml. Children with UTI showed highly elevated levels of sIgA amounting to 279 +/- 80 ug/ml (p<0.001). It was interesting to note that 96% of children and 76% of adults with UTI had sIgA level significantly above that of +/- 2SD of respective controls (287 +/- 99 and 80 +/- 48 ug/ml respectively). On culturing the urine obtained from these children the colonies identified were E. coil about 46%, Klebsiella about 24% and Pseudomonas about 24%. The sIgA antibody from urine samples assessed by indirect immunoflourescense. specifically reacted with the respective organism.

CONCLUSION

Taken together the results show that the presence of sIgA not only correlated with the UTI in children as well in adults but sIgA seems to be directed to the infective agent and can also be used to identify the type of infection. Thus measurement of urine antibody levels may provide an alternative marker of host responses to infection, which can be used either as a simple screening test or could be useful to assist alongwith other tests in establishing a diagnosis.

Erratum to “The role of P fimbriae for Escherichia coli establishment and mucosal inflammation in the human urinary tract”

Bacterial adhesion to the bladder mucosa is a critical step for the establishment of Escherichia coli bacteriuria. The P-fimbriae, encoded by the pap gene cluster, are considered as virulence factors but the mechanisms have been debated. This study defined the roles for P fimbriation during the early colonization of the human urinary tract. Patients with recurrent UTI were first subjected to deliberate colonization with the non-fimbriated ABU strain E. coli 83972. Bacteriuria was established long term (1-4 years) in patients with dysfunctional bladders, but not in the patients with normal bladder function. Super-infections were transient and asymptomatic. P fimbriated transformants of the ABU strain (E. coli 83972pap+/prs+) reached 105 CFU/ml more rapidly than E. coli 83972 and the vector control. This was demonstrated by group wise and intra-individual analysis in patients colonized on different occasions with E. coli 83972 or the P fimbriated transformants. Higher neutrophil numbers and IL-8 and IL-6 concentrations in urine were obtained after colonization with the P fimbriated transformants. These results demonstrated that transformation of E. coli 83972 with the pap sequences is sufficient to convert it to a more potent host response inducer. The P fimbriae were shown to lower the significant bacteriuria threshold. The P fimbriated transformants needed lower bacterial numbers (103-4 CFU/ml) to predict a positive second urine culture with a >80% accuracy and to trigger a significant host response. These studies show that P fimbriae fulfil the Koch Henles molecular postulates for bacterial establishment and host response induction in the human urinary tract.

The host response to urinary tract infection

The authors use the UTI model to identify basic mechanisms of disease pathogenesis, host response induction, and defense. Their studies hold the promise to provide a molecular and genetic explanation for susceptibility to UTI, and to offer more precise tools for diagnosis and therapy of these infections. There are few infections where the host response is understood in such detail and where pathologic host responses can be linked to distinct disease states. The susceptibility to UTI varies greatly in the population. The studies suggest that distinct molecular defects can cause the clinical entity of acute pyelonephritis with renal scarring, and suggest that the susceptibility to UTI in certain patient groups may have a genetic basis. In addition, the distinct signal transduction pathways explain the development of symptoms, and propose that defects in those signaling mechanisms may occur in patients with ABU. In the future, it may be useful to include these host response parameters in the diagnostic arsenal, to help in early detection of patients susceptible to recurrent UTI and renal scarring. These patients may then be offered therapies that strengthen their defense, and be offered close surveillance for recurrences and other complications.

Host defense mechanisms in urinary tract infections

The host response to urinary tract infections is directed against both bacterial surface antigens, as well as bacterial products. The local response is perhaps the most important, with prevention of binding and tissue invasion as the hallmarks. Once an infection is established, the humoral immune system is most active in curtailing the damage and clearing the infecting organism. The prostate has a specialized complex of defenses that serves to reduce the incidence of infections in males.

The office management of recurrent urinary tract infection and vesicoureteral reflux in children

Recurrent urinary tract infections (UTIs) and vesicoureteral reflux are common diagnosis' in infants and children who are referred to a urologist. Recurrent UTIs in these patients can be challenging, especially when radiographic evaluation reveals no structural abnormality. Prophylaxis and correction of voiding and bowel dysfunction are important treatment strategies. Febrile UTIs are commonly associated with reflux and should be treated aggressively to avoid renal scarring and its sequelae. Based on a comprehensive survey of the literature, long-term treatment strategies for children with reflux are now available.

Pathogenesis of urinary tract infection. Role of host defenses

In the last decade, there have been modest strides made in our understanding of the pathogenesis of urinary tract infections (UTIs). Matching the advances achieved in unraveling the complexities of bacterial virulence factors using molecular-genetic techniques has been a parallel increase in knowledge of host defense mechanisms. Host susceptibility to UTI in the past has been predominantly studied in patients with structural (obstruction) or functional abnormalities (diabetes mellitus); however, most patients with UTIs have no such demonstrable abnormalities, hence attention has now focused on host behavioral factors in addition to genetically determined cellular mechanisms that predispose to sporadic and recurrent UTI.

Urinary secretory immunoglobulin A and free secretory component in pyelonephritis

The immune defense mechanisms of mucosal surfaces involve secretory immunoglobulin A (sIgA) antibodies and, to a lesser degree, other specific and nonspecific immune factors. These antibodies are dependent on a secretory component (SC) for their transmission through the epithelium. This SC is also secreted without Ig as free SC (FSC). The kidney does produce these proteins; however, the ability of the lower urinary tract 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 normal controls (N = 33), cystitis patients (N = 22), and pyelonephritis patients (N = 27). Monoclonal antibodies binding to specific conformational epitopes were used in an enzyme-linked immunosorbent assay to detect the levels of sIgA and FSC in these groups. Previous sIgA measurements have been hampered by lack of specificity of the capture antibody. Urine creatinine was obtained to correct for the effect of diuresis. A one-tailed Student's t-test for nonparametric populations was performed to assess differences. The sIgA levels in the normal and cystitis groups were equivalent (1.4 micrograms/mg/mL and 1.3 micrograms/mg/mL, respectively; P = 0.32). When these two groups were compared with the pyelonephritis group (24.1 micrograms/mg/mL), a statistically significant difference was seen (P = 0.012 and P = 0.011, respectively), with no overlap. There was a statistical difference in the levels of FSC in these same groups, but a large degree of overlap.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of vaccination with inactivated uropathogenic bacteria in recurrent urinary tract infections of children

Secretory IgA (sIgA) is an important parameter in the predisposition to recurrent urinary tract infection (UTI). We investigated whether sIgA and frequency of UTI could be positively influenced by intramuscular vaccination with inactivated uropathogenic bacteria (Solco-Urovac). Ten otherwise healthy girls aged from 5 to 11 years (mean 9 1.7 years) with recurrent UTI were immunized with Solco-Urovac by i.m. injections three times at weekly intervals. A booster injection was given after 6 months. Urinary sIgA secretory component (SC) concentration was determined by radial immunodiffusion assay. Ten other age-matched girls with UTI were not immunized. Immunization therapy caused a significant reduction in the frequency of infection and an increase in urinary sIgA SC, while in the nonvaccinated group the values remained constant.

Urinary immunoglobulins in patients with continent urinary reservoirs and ileal conduits

BACKGROUND

Although bowel segments are commonly used for reconstructing the urinary tract, a high incidence of bacteriuria is observed in patients with urinary intestinal diversion. The normal gastrointestinal tract possesses a potent mucosal immune system characterized by secretory immunoglobulin A (sIgA) as the major humoral defense factor. However, the significance of urinary IgA secretion as the mucosal defense mechanism in patients with urinary intestinal diversion has remained obscure. In this study, urinary levels of sIgA as well as serum-type IgA were measured in patients with continent urinary reservoirs (Kock and Indiana pouches) and ileal conduits.

METHODS

Twenty-four-hour urine samples were collected in a total of 80 patients with urinary intestinal diversion (22 Kock pouch patients, 21 Indiana pouch patients and 37 ileal conduit patients). The amount of sIgA and serum-type IgA were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Urinary IgA levels showed great inter- and intra patient variability in all three groups. Indiana reservoir urine contained significantly greater amounts of sIgA (mean 32.0 mg/24 hrs) than Kock reservoir urine (11.9 mg) and conduit urine (4.9 mg), whereas Kock reservoir urine contained significantly more sIgA than conduit urine. However, the corresponding difference was not observed in regard to serum-type IgA. In none of the three modes of urinary diversion did 24-hour sIgA excretion show any correlation with the length of time after surgery.

CONCLUSIONS

Since the amounts of sIgA in these patients were much greater than reported in urinary tract infection as well as in normal subjects, the major portion of urinary sIgA seemed to be secreted by the intestinal segments. Long-term sIgA secretion in urinary intestinal diversion, especially continent urinary reservoirs, may be an important host defense system.

Suppressed antibody and interleukin-6 responses to acute pyelonephritis in pregnancy

This study examined the effect of pregnancy on the host response to acute pyelonephritis. Urine and serum samples were obtained at the time of diagnosis and after two weeks, from non-pregnant and pregnant women with acute pyelonephritis. The samples were analyzed for interleukin-6 (IL-6) and specific antibody activity to antigens extracted from the Escherichia coli strain infecting each patient. The host response to infection was further quantitated as fever, C-reactive protein, and renal concentrating capacity. Acute pyelonephritis in non-pregnant and pregnant women was accompanied by a significant serum and urine antibody response. The serum antibody response was significantly lower in the pregnant group. The IL-6 levels in serum and urine at diagnosis were significantly higher in the non-pregnant compared to the pregnant women. These results demonstrate that the immunosuppression of pregnancy includes the mucosal IL-6 and specific antibody responses to acute pyelonephritis caused by E. coli.

Controversies in the laboratory diagnosis of community-acquired urinary tract infection

Urine samples constitute the largest single category of specimens examined in most medical microbiology laboratories. The everyday nature and apparent simplicity of urinary tract infection belies the intense debate and controversy regarding the optimal methods of collection, transport and processing of urine specimens and reporting of results. There is considerable variation in the interpretation of quantitative culture results between laboratories and the etiology of abacterial cystitis remains unclear. Microscopy to detect pyuria provides information on an important indicator of inflammation and it has been proposed that detection of urinary antibody may provide similar information. Neither of these indices of host response is suitable for use in a screening test for urinary infection however, although they may usefully contribute to the interpretation of significance of culture results. The development of screening tests and automated systems continues, but at present microscopy and culture remain the most important techniques for laboratory diagnosis. However, these techniques have so far failed to provide an etiological diagnosis for abacterial cystitis and this remains a major area for research.

The pathobiology of subclinical pyelonephritis--an experimental evaluation

Clinical studies have demonstrated a poor correlation between localization tests, which are designed to determine the site of urinary tract infection, and symptoms of upper urinary tract infection. One explanation is that microorganisms may be present in the kidney but not initiate an inflammatory response with associated symptoms. An animal model has been developed to obtain quantitative information on the comparative pathobiology of lesion-inducing and non-lesion-inducing infections. In this model, non-manipulated kidneys had acquired a persistent microbial flora within 48 hours of the lower urinary tract becoming infected. This bacterial invasion was not associated with gross or histologic changes within the renal parenchyma, but minor foci of inflammatory cells were seen beneath the epithelium lining the calyces. Ureteric urines from such kidneys contained many leukocytes and high numbers of bacteria. These results showed that the kidneys were infected, rather than colonized, and the term "subclinical" infection was appropriate. Antimicrobial agents were variably successful at eradicating the infection. These experimental observations support the concept of subclinical pyelonephritis and may explain the absence of symptoms in the clinically equivalent situation in humans.

Urinary IgG antibody against mixed heat-killed coliform antigen and lipopolysaccharide core antigen

AIMS

To determine whether antibody to lipopolysaccharide-core (LPS-core) antigen is an important component of the antibody, detected by mixed heat-killed coliform antigen, in urine from patients with suspected urinary tract infection.

METHODS

LPS-core antigen and mixed heat-killed coliform antigen were used in an enzyme linked immunosorbent assay (ELISA) to measure IgG antibody in midstream urine samples. Seventy two samples from students attending their general practitioner with symptoms suggestive of urinary tract infection, six samples from which a Gram positive organism was isolated, and 16 asymptomatic controls were tested. Plates coated with LPS-core antigen were also used to absorb out the antibody detected by the mixed heat-killed coliform antigen.

RESULTS

Antibody to either antigen was associated with a positive culture, but neither was a useful predictor of a positive culture. There was a significant correlation between the results of the two assays (r = 0.7633; p less than 0.001), and absorption with LPS-core antigen did reduce the level of antibody to the mixed heat-killed coliform antigen. Antibody to both preparations was found in patients with Gram positive urinary tract infection.

CONCLUSION

Antibody to LPS-core antigen forms a substantial part of the antibody detected by mixed heat-killed coliform ELISA. The antibodies detected by these assays are probably the result of non-specific leakage of antibody into the urine, rather than a specific immune response.

Attenuation of antibody response to acute pyelonephritis by treatment with antibiotics

While acute pyelonephritis is known to elicit an antibody response, it is also known that a patient who has had pyelonephritis once is susceptible to recurrent renal infection. Using our experimental model of pyelonephritis in the monkey, we tested whether antibiotic therapy of the acute disease would affect the antibody response. We found that it did, because antibiotic therapy beginning 72 h after bacterial inoculation attenuated the antibody response so that rechallenge 3 months later produced acute pyelonephritis and prolonged bacteriuria. The animals with untreated infection had an antibody response that lasted a sufficient period of time to prevent acute pyelonephritis after renal challenge. We have confirmed that antibody titers against P fimbriae are protective, and to a degree, this protective effect may be abrogated by antibiotic therapy.

Ureteric catheterization in the diagnosis of pyelonephritis--an experimental evaluation

Experimental models of renal infections have been used to determine the accuracy with which the cellular and microbiologic components of ureteric and voided urine reflected the pathologic status of the kidney in pyelonephritis. In acute pyelonephritis, the composition of the ureteric urine reflected the pathologic status of the kidney, although in a few cases ureteric samples were either sterile or cell free. Animals with chronic pyelonephritis in which the lesions were either infected or sterile commonly had sterile ureteric urine. Pyuria, however, was demonstrable in both these situations. In subclinical pyelonephritis, ureteric samples from infected kidneys were variably culture positive, although pyuria was a common observation. Discriminate function analysis based on actual renal status and ureteric data gave an overall correct classification rate of 67% and demonstrated at least 80% agreement in four of the five classification groups.

Secretory immunoglobulin A in urinary tract infection, chronic glomerulonephritis, and renal transplantation

An enzyme-linked immunoassay (ELISA) for the quantitation of secretory IgA (S-IgA) in the urine is described. The assay is sensitive (linear down to 0.02 microgram/ml), specific, and reproducible (intraassay variation 7.8%, interassay variation 18.9%). The assay was used to determine the urinary excretion rates of S-IgA in patients with bladder catheter (n = 12), cystotomy and urinary tract infection (n = 13), urosepsis (n = 5), chronic glomerulonephritis, including IgA-nephritis (n = 31), in renal allograft recipients (n = 30), and in healthy controls (n = 46). An elevated S-IgA urinary excretion (P less than 0.01) was found in all patient groups studied. The highest values were observed in urosepsis. No significant differences between S-IgA levels in IgA-nephritis and other forms of chronic glomerulonephritis were detected. The elevated S-IgA excretion in renal allograft recipients indicates that immunosuppressive therapy does not influence the local S-IgA production in the urinary tract. The susceptibility of these patients to urinary tract infections is therefore not due to a S-IgA deficiency.

Local and systemic antibody responses accompany spontaneous resolution of experimental cystitis in cynomolgus monkeys

Cynomolgus monkeys were infected intravesically with two different strains of uropathogenic Escherichia coli. A quantitative enzyme-linked immunosorbent assay method was used to monitor secretory and serum immune responses to the induced cystitis. Anti-E. coli secretory immunoglobulin A (sIgA) and IgG urinary antibodies were generated as a result of the cystitis. Urinary sIgA levels against the E. coli strains tested were highest at 25 to 31 days after cystitis induction, and urinary IgG levels were highest at 31 to 45 days after induction. Anti-E. coli IgM was not detected in the urine. The antibody response in serum was characterized by IgM, IgG, and IgA immunoglobulin production. IgM levels in serum rose at 14 days after cystitis induction and were sustained for another 1 to 2 weeks. Increases in serum IgG levels began at 7 to 21 days of infection and persisted in some cases for up to 70 days. Serum IgA to the infecting E. coli was produced within 1 week after cystitis induction and remained at elevated levels throughout the course of the cystitis. These results demonstrate the capacity of primates to spontaneously resolve a cystitis and to mount both local and systemic immune responses against the infecting bacteria.

Urinary sIgA in children with urinary tract infection

Urinary secretory IgA (sIgA) was measured using a specific ELISA with insolubilized anti-IgA and enzyme-linked antisecretory component. This test was applied to unprocessed urine from healthy children and from children with urinary tract infection. Normal range was a function of age. In 175 healthy children the excretion rate of sIgA was low in infants younger than 6 months but was constant between ages 6 months to 15 years (median 0.69 mg/gm creatinine, range 0.15 to 3.4 mg/gm creatinine), whereas sIgA concentration (milligrams per liter of urine) increased continuously with age. No sex difference was noted. There were no significant circadian changes or day-to-day variability. Thirty girls, age 1 to 16 years, were examined; they had a history of recurrent symptomatic episodes of urinary tract infection but had anatomically normal tracts and no symptoms, and no bacteriuria at the time of study. sIgA excretion rate was significantly lower (0.45 mg/gm, creatinine, 0.08 to 0.75 mg/gm creatinine) than in controls. In contrast, 11 girls examined at the time of symptomatic urinary tract infections, and who had normal urinary tracts, had significantly (P less than 0.01) higher sIgA excretion rates (1.4 mg/gm creatinine, 0.8 to 3.4 mg/gm creatinine) than those in either control subjects or girls without symptoms at the time of study. Urinary sIgA excretion rates were highest (2.0 mg/gm creatinine, 0.44 to 3.69 mg/gm creatinine) in children with symptomatic urinary tract infections who had an abnormal urinary tract. We conclude that low urinary sIgA values may be a marker for recurrent symptomatic bacteriuria in girls with normal urinary tracts.

Urinary IgA in IgA nephropathy and Henoch-Schoenlein purpura

To determine the concentrations and molecular forms of urinary IgA in IgA nephropathy and Henoch-Schoenlein purpura, we studied 29 patients with these IgA-associated renal diseases (IgAN). Control groups comprised 10 patients with other diverse renal disease and 11 healthy volunteers. Urinary IgA and IgG concentrations were higher in IgAN than in either control group and correlated positively with the serum creatinine concentration as well as the urinary protein excretion (P less than 0.01). However, IgA/IgG ratios did not differ among the three groups. Polymeric IgA (p-IgA) in the urine predominated only in normals; in IgAN and patients with other renal diseases, monomeric IgA (m-IgA) occurred almost exclusively. Serum IgA concentrations were generally normal in IgAN; four patients had concentrations greater than 500 mg/dl. Although the fraction of p-IgA in serum (median, 18%) was increased above normal (5-10%) in 13 of 16 (81%) subjects, neither the concentration of IgA or IgG nor the amount of p-IgA correlated with the serum creatinine concentration. These data suggest that the molecular form and concentration of urinary IgA are not discriminating for IgAN and are independent of these characteristics of serum IgA.