Biomedical subjects

L A DeBruyne

Publications and source records attributed to L A DeBruyne.

5 recordsLinked to original sources

PubMed1996

Restricted V beta usage by T cells infiltrating rejecting human lung allografts.

TCR expression was evaluated in lung transplant patients to determine whether T cells infiltrating rejecting lung allografts employed restricted V beta elements. Serial bronchoalveolar lavage (BAL) specimens were obtained from six lung transplant recipients at approximately 3 wk, 6 wk, and 3 mo post-transplant. T cell lines were established by culturing lavage cells with irradiated donor splenocytes in the presence of low dose IL-2 for 3 wk, and TCR V beta usage was determined by quantitative reverse transcriptase-PCR. Patients were grouped into three categories based on TCR V beta profiles and the clinical status of the allograft. 1) In one patient, BAL-derived T cells expressed heterogeneous V beta repertoires at all time points evaluated. This patient did not experience graft rejection during the 16-mo period of observation, though respiratory infections were diagnosed. 2) In three patients, V beta usage by BAL-derived T cells was restricted during allograft rejection episodes, but was heterogeneous in the absence of rejection and during respiratory infections. In one of these patients, similar V beta repertoires were employed by BAL cells during multiple rejection episodes. 3) In two patients, restricted V beta usage by BAL-derived T cells was observed before and during rejection episodes. Collectively, these data illustrate that human lung allograft rejection, but not pulmonary infection, is associated with T cells expressing a limited number of V beta families. Restricted V beta usage by graft-reactive T cells may allow for the selective elimination of these cells using TCR-specific reagents, thereby promoting allograft-specific tolerance.

Bronchoalveolar Lavage Fluid↗

PubMed1995

In vivo depletion of CD8+ T cells results in Th2 cytokine production and alternate mechanisms of allograft rejection.

A current hypothesis states that Th1 cytokines promote allograft rejection and that Th2 cytokines promote graft acceptance. We present data that question the tolerogenic activity of Th2 cytokines, and we suggest that Th2 cytokines may evoke allograft rejection by recruitment of alternate effector mechanisms. Unmodified rejection of mouse heterotopic cardiac allografts is associated with the accumulation of large numbers of donor-reactive CD8+ CTL within the allograft, which is indicative of a Th1-driven cellular response. However, when recipients are depleted of CD8+ CTL, rejection still occurs and is associated with an aggressive cellular infiltrate rich in eosinophils, large mononuclear cells, and fibroblast-like cells. Eosinophils, which are responsive to the Th2 cytokines IL-4 and IL-5, are not present in unmodified rejecting allografts. Differential production of Th1 versus Th2 cytokines was further suggested by altered levels of IgG2a (promoted by IFN gamma) and IgG1 (promoted by IL-4) alloantibody in the sera of these mice; IgG2a dominated the alloantibody response in unmodified allograft recipients, whereas IgG1 levels increased in recipients depleted of CD8+ CTL. Altered intragraft cytokine gene expression was verified by RT-PCR; Th1 (IL-2, IFN gamma), but not Th2 (IL-4, IL-5, IL-10), cytokine mRNAs were readily detectable in the allografts of unmodified recipients. In contrast, both Th1 and Th2 cytokine genes were expressed in the allografts of mice depleted of CD8+ CTL. These data suggest that donor-reactive CD8+ CTL inhibit intragraft production of Th2 cytokines, thereby promoting a Th1 dominated-rejection response. Elimination of CD8+ cells allows Th2 cytokine production, which may have deleterious, rather than protective, effects.

Animals↗

PubMed1995

Evidence that human cardiac allograft acceptance is associated with a decrease in donor-reactive helper T lymphocytes.

We have reported that acute cardiac allograft rejection is associated with increased numbers of donor-reactive helper T lymphocytes (HTL) in the peripheral blood of patients. Further, increased frequencies of circulating donor-reactive HTL may predict allograft rejection episodes diagnosed by endomyocardial biopsy. The present study evaluates the relationship between donor-reactive HTL and allograft "acceptance" in cardiac transplant recipients bearing long-term allografts (> 1 year). Patients were categorized as either long-term acceptors or persistent rejecters based on the number of rejection episodes and the ability to withdraw steroid therapy. Limiting dilution analysis for IL-2-producing HTL was utilized, with cadaver donor splenocytes as a source of donor alloantigens. Donor-reactive HTL frequencies were determined from peripheral blood samples obtained before transplant, and at 1 month and 1 year after transplant. Individuals who accommodated their allografts and were withdrawn from steroid therapy had reduced numbers of donor-reactive HTL at 1 year after transplant as compared with earlier time points. Further, PBMC obtained from these individuals at 1 year after transplant responded weakly to donor alloantigens in a mixed lymphocyte response (MLR). This relationship between donor-reactive HTL and allograft accommodation was exemplified in a cardiac/liver transplant patient who was diagnosed with progressive multifocal leukoencephalopathy and removed from all immunosuppression. No subsequent rejection episodes were diagnosed. Donor-reactive HTL were not detectable and this individual failed to mount an MLR to donor alloantigens. However, a vigorous donor-reactive response was observed when MLR cultures were supplemented with exogenous IL-2. Therefore, nonresponsiveness to the allograft appeared to be due to a deficit in IL-2 production. In contrast, patients who experienced persistent rejection episodes and required continued steroid therapy maintained large numbers of donor-reactive HTL at 1 year after transplant. PBMC from these individuals responded vigorously to donor alloantigens in an MLR. Hence, monitoring donor-reactive HTL may identify individuals who have accommodated their graft and may tolerate a reduction in immunosuppression.

Graft Rejection↗

PubMed1995

Dissociation of mouse cardiac transplant rejection and donor alloantigen-specific T cell responsiveness.

Mouse hearts transplanted into MHC disparate donors are usually rejected 1 week after placement. It is widely accepted that alloantigen-reactive helper T lymphocytes (HTL) and cytotoxic T lymphocytes (CTL) are the key mediators of acute allograft rejection. This report demonstrates that the presence or absence of 'traditional' graft-reactive HTL and CTL is not necessarily related to allograft survival. In these studies, donor/recipient combinations disparate only at MHC or only at minor histocompatibility (mH) loci were employed. Allograft survival was monitored, donor-reactive IL-2 (interleukin-2) producing HTL and CTL were quantified by modified limiting dilution analysis, and serum levels of cytolytic alloantibody were determined. C57BL/10 hearts (H-2b) transplanted into B10.BR (H-2k) recipients (full MHC disparity) enjoyed prolonged survival despite massive infiltration of the allograft by donor-reactive HTL and CTL. IgM, but not IgG, donor-reactive alloantibody was present in the sera of these mice. Hence, traditional IL-2 producing HTL and CTL were not capable of mediating acute graft rejection, nor of providing help for alloantibody isotype switching in this MHC disparate combination. In contrast, C3H/HeN (H-2k) hearts transplanted into B10.BR (H-2k) recipients (mH disparity only) were acutely rejected. Donor-reactive HTL and CTL were rare or not detectable in these recipients, and cytolytic alloantibody was not detectable. Similar observations were made when B10.BR hearts were transplanted into C3H/HeN recipients. Interestingly, treatment of recipients with anti-CD4 monoclonal antibody prevented rejection of mH disparate allografts. Therefore, CD4+ T cells were required for rejection of mH disparate allografts, but this process was independent of detectable IL-2 production or CTL function. Hence, the significance of monitoring 'traditional' T cell functions should be questioned in certain donor/recipient combinations.

Animals↗

PubMed1993

Increased frequency of alloantigen-reactive helper T lymphocytes is associated with human cardiac allograft rejection.

Endomyocardial biopsy (EMB) is the standard method of monitoring heart transplant recipients for the development of allograft rejection. To date, noninvasive methods to detect cardiac allograft rejection have lacked adequate sensitivity and specificity for wide clinical application. In this study, limiting dilution analysis (LDA) was used to quantitate the number of donor alloantigen-reactive helper T lymphocytes (HTLs) in the peripheral blood of cardiac transplant recipients. Cadaveric donor splenocytes were cryopreserved, providing a source of donor alloantigenic stimulation for these assays. Peripheral blood mononuclear cells were harvested from cardiac transplant recipients before transplantation and at the time of EMB. LDA of donor-reactive HTLs was conducted simultaneously on all time points to minimize experimental variation, and these data were related to EMB scores. Frequencies of donor-reactive HTLs in pretransplant samples were highly variable, ranging from 1/1381 to < 1/200,000, and correlated poorly with the degree of HLA disparity. During episodes of moderate rejection, donor-specific HTL frequencies increased an average of 6 times their post-transplant baseline frequency. Additionally, 10-fold increases in HTL frequencies were seen preceding EMB-diagnosed rejection in several individuals. These data indicate that episodes of allograft rejection are associated with increases in the number of circulating donor-reactive HTL which are frequently detected before the development of histologically defined rejection. Thus, monitoring HTL frequencies may serve as a non-invasive method for detecting and predicting cardiac allograft rejection. Furthermore, this assay may provide a valuable means of assessing the in vivo efficacy of various immunosuppressive therapies.

Graft Rejection↗