This report describes a detailed analysis how donor-specific HLA class II epitope mismatching affects antibody reactivity patterns in 75 solid organ transplant recipients with an in situ allograft and who were considered for retransplantation. Sera were tested for antibodies in a sensitive antigenbinding assay (Luminex) with single class II alleles. Their reactivity was analyzed with HLAMatchmaker, a structural matching algorithm that considers so-called eplets to define epitopes recognized by antibodies. Only 24% of the patients showed donor-specific anti-DRB1 antibodies and there was a significant correlation with a low number of mismatched DRB1 eplets. This low detection rate of anti-DRB1 antibodies may also be due to allograft absorption. In contrast, antibodies to DRB3/4/5 mismatches were more common. Especially, 83% of the DRB4 (DR53) mismatches resulted in detectable antibodies against an eplet uniquely found on DR53 antigens. Donor-specific DQB mismatches led to detectable anti-DQB antibodies with a frequency of 87%. Their specificity correlated with eplets uniquely found on DQ1-4. The incidence of antibodies induced by 2-digit DQA mismatches was 64% and several eplets appeared to play a dominant role. These findings suggest that both α and β chains of HLA-DQ heterodimers have immunogenic epitopes that can elicit specific antibodies. About one-third of the sera had anti-DP antibodies; they reacted primarily with two DPB eplets and an allelic pair of DPA eplets.These data demonstrate that HLA class II reactive sera display distinct specificity patterns associated with structurally defined epitopes on different HLA-D alleles.
Hematogenous pyelonephritis was produced in rats utilizing multiple strains of Escherichia coli, a strain of Klebsiella pneumoniae, and a strain of Proteus mirabilis. Three patterns of hematogenous pyelonephritis occurred which represent an interrelationship between an immune response to the infecting bacteria and the development of obstructive uropathy as a consequence of infection. First, the course of pyelonephritis due to strains of Escherichia coli was acute, self-limited, and associated with the development of circulating agglutinins. Following healing, this pattern of infection was associated with acquired resistance to reinfection with the same bacterial strain. Second, the course of pyelonephritis due to a strain of Klebsiella pneumoniae type C was chronic. This infection was not associated with the production of circulating agglutinins against encapsulated strains. Acquired resistance to reinfection by the homotypic strain could not be demonstrated following eradication of infection but was produced by the passive transfer of concentrated antiserum. Third, pyelonephritis due to Proteus mirabilis was associated with circulating agglutinins and resistance to reinfection with the same organism following eradication of infection, yet the course was chronic. The chronicity appeared to be the consequence of obstructive uropathy resulting from calculi which developed during the course of the infection. Resistance to reinfection was demonstrated in infections with strains of E. coli and P. mirabilis. The resistance is associated with specific immunity as demonstrated by the observation that: (a) it is type-specific, (b) it is of at least 3 months' duration, and (c) it can be passively transferred by means of rabbit antiserum. Since K. pneumoniae failed to evoke capsular antibodies in the rat, resistance to infection with K. pneumoniae was produced only by means of passively transferred concentrated rabbit antiserum and not by prior infection. Immunity can be demonstrated to have a significant role in the pathogenesis of experimental hematogenous pyelonephritis only in the absence of obstructive uropathy.
1. Hematogenous E. coli pyelonephritis was produced in rats. The localization of the organisms and the persistence of bacterial antigens was followed by fluorescent antibody techniques as well as by standard histological and bacteriological methods. 2. Salient sequential features were as follows: Single organisms passed through vessel walls into the renal interstitium and began multiplication and subsequently evoked a leucocytic response. Bacterial multiplication did not occur in glomeruli or renal tubular cells. Bacteria did not appear within renal tubular lumina until microabscesses were well developed in the renal interstitium. Bacteriuria appeared late and represented secondary invasion rather than filtration of organisms. The infection healed spontaneously but, while sterile, the parenchymal scars contained large amounts of residual bacterial antigen. The persistence of bacterial antigen did not result in continuing inflammatory changes or progressive scarring. 3. The persistence of bacterial antigens is postulated to constitute a major antigenic stimulus responsible for active immunity in experimental hematogenous pyelonephritis.
Retrograde pyelonephritis was produced in rats by the intravesical injection of Proteus mirabilis. When animals were preimmunized against Proteus mirabilis by (a) prior infection, (b) administration of antigen, or (c) passively transferred antiserum, they were resistant to infection by proteus when challenged by the retrograde route. The protective effect of specific preimmunization in retrograde pyelonephritis indicates that a major site of action is retardation of bacterial growth within the parenchyma of the kidney.
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