Immunologic Response of the Prostate to Bacteriuria and Bacterial Prostatitis II. Antigen Specific Immunoglobulin in Prostatic Fluid

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Abstract
An indirect solid-phase radioimmunoassay was used to quantitate Ig binding to formalin-fixed Escherichia coli in expressed prostatic secretion (EPS). EPS samples from 20 men with no histories of bacteriuria, from 8 men with histories of culture proven E. coli bacteriuria but with no clinical or bacteriologic evidence of prostatic infection and from 5 men with culture proven E. coli bacterial prostatitis were assayed. Measurable binding of IgA to E. coli was observed for EPS samples from all the infected patients but from only 1 of the uninfected controls. Measurable binding of IgG to E. coli was observed for samples from 7 of 8 infected patients and from 2 of 10 uninfected controls. In no cases was there measurable IgM binding to E. coli. There was no measurable binding of IgA to formalin-fixed Staphylococcus epidermidis; and no measurable binding of IgA to formalin-fixed Klebsiella pneumoniae, Proteus mirabilis or Pseudomonas aeruginosa for samples from patients who had not been previously infected with these gram negative bacilli. Absorption of immune EPS with suspensions of these bacteria did not alter the binding of IgA to E. coli but absorption with a suspension of E. coli completely eliminated this binding. The magnitude and specificity of EPS Ig binding to E. coli was similar for the bacteriuric and bacterial prostatitis patients. Serum from 8 infected patients was assayed for Ig binding to E. coli. The per cent of serum IgG binding to E. coli for these patients was similar to that of EPS IgG, but the per cent of EPS IgA binding to E. coli was 3.5-147.5 times greater than that of serum IgA. In 1 patient with bacteriuria due to bacterial prostatitis, the concentrations of EPS IgG and EPS IgA binding to E. coli were 53 and 217 times greater, respectively, than those of a 1st voided urine specimen. Absorption of immune EPS with rabbit anti-human-secretory component indicated that > 70% of the IgA directed against E. coli was in the form of secretory-IgA. Thus, E. coli bacteriuria and E. coli bacterial prostatitis evidently are associated with the local secretion of antigen specific IgA in prostatic fluid that appears to be independent of the systemic immune response. The prostate gland evidently is usually colonized during episodes of urinary tract infection, however, symptomatic or chronic infection seemingly is prevented by the secretion of antigen specific IgA.