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Biomedical subjects

A H Balk

Publications and source records attributed to A H Balk.

At least 73 records · Page 4Linked to original sources
PubMed1997

Kinetics of IL-2 and IL-4 mRNA and protein production by graft-infiltrating lymphocytes responsible for rejection after clinical heart transplantation.

During cardiac rejection we studied the kinetics of IL-2 and IL-4 mRNA and subsequent protein production by in vivo primed graft-infiltrating lymphocytes (GIL), using semiquantitative RT-PCR and ELISA. Following in vitro stimulation with either donor or third-party antigens, mRNA expression of IL-2 and IL-4 were already detectable 1-2 h after stimulation, while their protein production could be measured from 4 h onwards at least until 48 h. At both the mRNA and protein level, we measured a donor-specific signal for IL-2 and for IL-4 production (p = 0.02), while the relative donor-specific IL-2 mRNA level was significantly higher than the relative IL-4 mRNA level (p = 0.002). These observations suggest that after in vitro challenge with donor antigens, GIL obtained from rejecting cardiac allografts predominantly produce IL-2 mRNA and protein.

Biopsy↗
PubMed1997

The avidity of allospecific cytotoxic T lymphocytes (CTL) determines their cytokine production profile.

Donor-specific CTL present within the cardiac allograft during a rejection episode are distinct from those that populate the cardiac allograft in the absence of rejection. Whereas the former generally have a high avidity for donor cells, the latter mainly have a low avidity for donor cells. This observation made us reason that high-avidity CTL are implicated in transplant rejection, whereas low-avidity CTL are not. In the present study, we analyse whether both CTL subsets were distinct with respect to their IL-2, IL-4, IL-6 and interferon-gamma (IFN-gamma) secretion pattern. CTL clones with either a high or a low avidity for donor antigens were stimulated with donor cells, third party cells, or immobilized anti-CD3 MoAb and the amount of cytokine released was measured. High- and low-avidity CTL clones were found to differ with respect to their IFN-gamma production profile. Stimulation with donor cells resulted in IFN-gamma secretion by high-avidity CTL clones, but not by low-avidity CTL clones. CD3 stimulation, in contrast, led to secretion of equivalent amounts of IFN-gamma by both CTL subsets. These observations indicate that low-avidity CTL are fully capable of producing IFN-gamma, but, in contrast to high avidity CTL, fail to do so when they encounter donor cells. As IFN-gamma favours the occurrence of transplant rejection, this observation emphasizes the relevance of high-avidity CTL in the rejection process. Additionally, the data show that the cytokine production profile of CTL depends on the nature of the stimulus.

Antibodies, Monoclonal↗
PubMed1997

Effect of adopting a new histological grading system of acute rejection after heart transplantation.

BACKGROUND: Treatment policy of acute rejection after heart transplantation has been changed after adopting the ISHLT endomyocardial biopsy grading system in 1991. OBJECTIVE: To determine the effect of this policy change on clinical outcome after transplantation. METHODS: The outcome of 147 patients who had a transplant before (early group, median follow up 96 months) and 114 patients who had a transplant after (late group, median follow up 41 months) the introduction of the ISHLT biopsy grading system was studied retrospectively. Initially "moderate rejection" according to Billingham's conventional criteria was treated. From January 1991 grade 3A and higher was considered to require intensification of immunosuppression. RESULTS: There were some differences between the two groups: recipients (50 v 44 years) as well as donors (28 v 24 years) were older in the "late group" and more patients of this group received early anti-T cell prophylaxis (92% v 56%). Despite more extensive use of early prophylaxis more rejection episodes were diagnosed (2.4 v 1.4) and considerably more courses of rejection treatment were instituted in the late compared with the early group (3.2 v 1.5). There were no deaths because of rejection in the late group, however, more infections occurred within the first year (mean 1.8 v 1.4) and more non-skin malignancies within the first 41 months were diagnosed (8 of 57 v 6 of 147, 95% CIs of difference includes 0). The incidence of graft vascular disease in the late group has been comparable to the early group until now. CONCLUSION: The interpretation of the ISHLT grading system resulted in lowering of the threshold for the diagnosis of rejection thereby increasing the number of rejections and subsequently the immunosuppressive load and its complications.

Acute Disease↗
PubMed1997

Cytotoxicity of graft-derived lymphocytes: specific for donor heart endothelial cells?

BACKGROUND: Previously, we showed that lymphocytes cultured from cardiac allografts can lyse lymphoid cell lines from donor origin. Because endothelial cell form the first allogeneic barrier to be encountered in vivo, the reactivity of graft-infiltrating cells against donor heart-derived endothelial cells (DoHEC) may be more relevant for understanding the clinical course after heart transplantation. METHODS: Endomyocardial biopsies (EMB) were taken at different times after transplantation, both during acute rejection and during quiescence. Lymphocytes cultured from these EMB were assayed for cell-mediated cytotoxicity in a 4-hour chromium 51 release test by use of target panels of different cell types derived from donor or third party. Cell specificity was investigated by addition of a tenfold excess of unlabelled target cells to 51Cr-labeled DoHEC. RESULTS: These experiments show that DoHEC can be lysed by lymphocytes derived from EMB. Antigens that were recognized on DoHEC were often donor human leukocyte antigen class I antigens. Some cultures in addition recognized alloantigens present only on DoHEC and not on donor-derived B cells as suggested by lack of or partial inhibition of DoHEC lysis by addition of excess competitor B cells. Endothelial cell-specific reactivity was unequivocally identified after limiting dilution of EMB-derived cultures. CONCLUSION: We conclude that not only DoHEC-reactive but also DoHEC-specific cells are present among the cardiac graft infiltrating cells.

CD8-Positive T-Lymphocytes↗
PubMed1997

The avidity, not the mere presence, of primed cytotoxic T-lymphocytes for donor human leukocyte class II antigens determines their clinical relevance after heart transplantation.

BACKGROUND: To analyze the relevance of CD4-positive cytotoxic T-lymphocytes (CTL) in clinical heart rejection, we studied the frequency and avidity of donor human leukocyte antigen class II-specific CTL present within the graft during a rejection episode and during a period without rejection. METHODS: For this analysis endomyocardial biopsies of heart transplant recipients were cultured to obtain graft-infiltrating lymphocytes (GIL). GIL cultures exhibiting donor class II-directed cytotoxicity were considered for this study. With limiting dilution analysis, the frequency of donor class II-specific CTL that had been primed by donor antigens in vivo (designated cCTL) was determined in GIL cultures established from endomyocardial biopsies taken during a rejection episode (n = 10) or during a period without rejection (n = 11). Addition of anti-CD4 to the limiting dilution analysis revealed the fraction of donor class II-specific cCTL having a high avidity for donor antigen. RESULTS: During a rejection episode, 196 (median) donor class II-specific cCTL/106 GIL were present. In a period without rejection, the frequency of donor class II-specific cCTL was not significantly different (median = 330/10(6); p = 0.1). Addition of anti-CD4, however, revealed that donor class II-specific cCTL with a high avidity for donor antigen are predominant during a rejection episode (median = 100%) but are in minority during a period without rejection (median = 35%; p < 0.0001). CONCLUSIONS: These results suggest that graft-infiltrating CD4+ CTL can mediate heart rejection provided they have a high avidity for donor antigen.

Antibody Affinity↗
PubMed1996

Progressive accumulation of CTL with high avidity for donor antigens during the development of acute cardiac rejection.

To study the importance of cytotoxic T lymphocytes (CTL) with high avidity for donor antigens (Ag) in the development of acute cardiac allograft rejection, their appearance within the graft in relation to rejection was analyzed. For this study, donor directed CTL propagated from sequentially taken endomyocardial biopsies (EMB) were enumerated by limiting dilution analysis (LDA). Subsequentially, the fraction of these CTL having high avidity for donor Ag was determined by addition of a CD8 monoclonal antibody (mAb) to the cytotoxic phase of the LDA. Analysis of 37 EMB cultures obtained from 11 heart transplant (HTx) patients before, during, or after they experienced rejection, revealed the kinetics of donor specific CTL in relation to rejection for HTx patients in general. For 5 individual recipients, a more detailed analysis was performed. The kinetics found for individual patients confirmed the pattern found for the total group of HTx recipients tested. Frequencies of donor specific precursor CTL (pCTL) as well as of in vivo primed donor reactive CTL (committed CTL or cCTL) increased towards rejection and decreased after successful rejection therapy. More than 2 weeks before rejection was diagnosed, only a small fraction of the graft infiltrating donor specific pCTL and cCTL had high avidity for donor Ag (median = 35% and 11%, respectively). Within 2 weeks preceding rejection, this fraction increased gradually (median = 52% and 55%, respectively) and became dominant during rejection (median = 87% and 78%, respectively). After successful rejection therapy, a decrease to basal levels (median = 18% and 24%, respectively) was observed. Conclusively, intragraft accumulation of high avidity, donor specific pCTL and cCTL may cause transplant rejection.

Acute Disease↗
PubMed1996

Human heart endothelial-cell-restricted allorecognition.

We studied the reactivity of cardiac graft-infiltrating cells, cultured from endomyocardial biopsy specimens, toward heart endothelial cells (Hec). In two cases, Hec derived from the specific donor heart or Hec compatible with the donor were lysed, but not the syngeneic B cell line. A vessel-derived endothelial cell line was not lysed. Panel studies suggest that the epitopes recognized are, in one case, a Hec-specific peptide presented in the context of HLA-Bw41 and, in the other case, a Hec-specific peptide presented by a subtype of HLA-B44. In conclusion, we showed that cardiac graft-infiltrating cells cultured from endomyocardial biopsy specimens can exhibit cytotoxic reactivity specifically directed against HLA-peptide complexes on Hec.

Cell Line↗
PubMed1996

A randomized trial comparing safety and efficacy of OKT3 and a monoclonal anti-interleukin-2 receptor antibody (BT563) in the prevention of acute rejection after heart transplantation.

In a prospective randomized trial, BT563, a murine IgG, anti-interleukin-2 receptor antibody, was compared with OKT3 for use as an early rejection prophylaxis after heart transplantation. Patients received either BT563 (n=31) or OKT3 (n=29) during the first 7 days after transplantation; cyclosporine was started on day 3. Median follow-up was 34 months. A cytokine release syndrome occurred in the majority of patients of the OKT3-treated group but in none of the BT563 recipients. The mean duration of electrical stimulation of the heart in the BT563 group was longer than in the OKT3 group (5.1 vs. 2.1 days). In both groups, one patient required insertion of a permanent pacemaker. Freedom from acute rejection at 3 months was not significantly different between the two groups (BT563: 5/29, 17%; OKT3: 6/29, 21%). In the BT563 group, however, rejection tended to occur earlier after transplantation. There was no difference in the overall incidence of rejection. The incidence of infectious complications was evenly distributed in both groups. Malignancies occurred in two patients, both in the OKT3 group. In conclusion, the use of this anti-interleukin-2 receptor monoclonal antibody in heart transplant recipients is safe and devoid of the side effects that accompany the use of OKT3. OKT3 and BT563 result in a similar freedom from rejection at 3 and 12 months after heart transplantation.

Adolescent↗
PubMed1996

Peripheral monitoring of direct and indirect alloantigen presentation pathways in clinical heart transplant recipients.

It has been reported that the response to alloantigens presented by the direct and indirect pathway may be of differential relevance after human kidney transplantation. Accordingly, we monitored these routes in peripheral blood mononuclear cells (PBMC) of heart transplant patients from before transplantation and up to 2 years thereafter in an attempt to find a correlation with the clinical status of the patients. Both before and after transplantation, comparable proportions of PBMC samples reacted in mixed lymphocyte culture to nondepleted donor spleen cells (direct route), but never to donor cells depleted for antigen-presenting cells (indirect route). In contrast, the latter route could easily be activated by a nominal antigen and persisted after transplantation, although the proportion of PBMC samples responding was significantly suppressed, irrespective of the occurrence of rejection. Consequently, complete removal of antigen-presenting cells from the stimulator population in a mixed lymphocyte culture with PBMC as responder is not a suitable tool for measuring indirect presentation of alloantigens, and therefore not relevant for monitoring the immunological status of heart transplant recipients.

Antigen Presentation↗
PubMed1996

Phenotypic analysis of lymphocytes infiltrating human cardiac allografts during acute rejection and the development of graft vascular disease.

Acute rejection (AR) and graft vascular disease (GDV) are processes mediated, at least in part, by cellular processes. Therefore, we cultured graft-infiltrating lymphocytes (GIL) from endomyocardial biopsies (EMB) taken during the first year after transplantation, determined their phenotypic composition, and correlated it to AR and GVD. We observed more often GIL growth from EMB with AR than from non-rejection EMB (P = 0.02), but no difference was found between patients with and without GVD 1 year after transplantation. CD4+ cells were always more numerous than CD8+ cells, and no difference in phenotypic composition was found between AR and non-rejection EMB nor between EMB derived from patients with or without signs of GVD. In conclusion, AR is correlated with cell growth of EMB, but the development of GVD is not associated with AR, GIL growth from EMB, or their phenotypic composition.

Acute Disease↗
PubMed1996

Patterns in donor-specific mRNA and protein production of Th1 and Th2 cytokines by graft-infiltrating lymphocytes and PBMC after heart transplantation.

We used RT-PCR and ELISA to study the kinetics of IL-2 (Th1) and IL-4 (Th2) both on mRNA and protein level from "naive" PBMC and "primed" graft-infiltrating lymphocytes (GIL) obtained from a heart transplant recipient. For this purpose, these cells were stimulated for 1-48 h with donor and control third-party antigens. Only stimulation of GIL with donor-specific antigen resulted in early detectable IL-2 and IL-4 mRNA and protein levels. Maximal relative IL-2 mRNA levels were significantly higher than maximal relative IL-4 mRNA levels (100-fold) in both GIL and PBMC after donor-specific stimulation. This was accompanied by a maximum protein production of 908 pg/ml IL-2 and 19 pg/ml IL-4 by GIL, and of 82 pg/ml IL-2 and undetectable IL-4 production by PBMC. These results suggest that, after stimulation donor-specific "primed" GIL, and not "naive" PBMC, rapidly produce abundant levels of IL-2 (Th1) and IL-4 (Th2) at both the transcriptional and protein level.

Cells, Cultured↗
PubMed1996

Evidence that cyclosporin A prevents clinical cardiac allograft rejection by blocking both direct and indirect antigen presentation pathways.

Monitoring for the responses to alloantigens presented either by the direct or the indirect presentation pathway have been reported to be of clinical value after kidney transplantation. Amongst others, the level of these responses may be dependent on the immunosuppressive treatment. We studied both presentation routes in peripheral blood mononuclear cells (PBMC) of cardiac transplant patients, who experienced episodes of rejection, and related them to the in vivo cyclosporin A (CsA) levels in plasma. PBMC of the recipients were stimulated with irradiated donor cells to determine the direct presentation pathway. As a method for the activation of the immune response via the indirect pathway, PBMC were stimulated with tetanus toxoid. Both immune responses increased when CsA levels inadvertently decreased to inadequate concentrations and histological rejection was diagnosed. After clinical heart transplantation, CsA may prevent rejection by blocking both the direct and the indirect antigen presentation pathway.

Antigen Presentation↗
PubMed1996

Sustained decrease of serum total IgE in cardiac transplant recipients.

A steady decrease in serum IgE was noted in cardiac transplant recipients receiving a combination of cyclosporin A and prednisolone for immunosuppressive therapy. The average time period for the demonstration of a 50% decrease in serum IgE levels was calculated to be 40 +/- 16 days in 19 patients.

Cyclosporine↗
PubMed1996

Donor-derived human leukocyte antigen class I proteins in the serum of heart transplant recipients.

BACKGROUND: Human leukocyte antigen class I proteins are expressed on most cell types in all organ allografts but are constitutively secreted only by certain organs, for example, the liver. We hypothesized that detectable levels of donor-derived human leukocyte antigen proteins would be released from transplanted cardiac allografts only when the allograft was immunologically stimulated, that is, during rejection and perhaps during viral infection. If so, then the release of donor human leukocyte antigen might be a noninvasive monitor of these events. METHODS: We used an enzyme-linked immunosorbent assay to detect donor-derived human leukocyte antigen-A2 in the serum of 21 human leukocyte antigen-A2 negative recipients of human leukocyte antigen-A2-positive heart transplants. The level of donor human leukocyte antigen-A2 during the first 100 days after transplantation was correlated with the clinical status of the patient. RESULTS: We found little or no donor human leukocyte antigen in the serum of heart transplant recipients whose postoperative clinical course was unremarkable for infection or rejection. We did find donor-derived human leukocyte antigen in the serum of heart transplant recipients transiently in the week immediately after transplantation, continuously from patients in whom chronic rejection was developing, during cytomegalovirus infection, and during some, but not all, acute rejection episodes as determined by endomyocardial biopsy. CONCLUSIONS: These findings are consistent with the hypothesis that the donor human leukocyte antigen serum level reflects vascular diseases, rather than myocardial disease in the transplanted heart. Therefore, the serum level of donor human leukocyte antigen cannot be used as a monitor of cellular infiltration and myocyte damage as currently assessed by endomyocardial biopsy but may be an early indicator of the development of vascular disease such as chronic rejection.

Biopsy↗
PubMed1996

The intragraft cytokine mRNA pattern reflects the efficacy of steroid antirejection therapy.

BACKGROUND: We studied the effect of antirejection therapy on intragraft cytokine mRNA expression. METHODS: Therapy consisted of three doses of 1 gm of intravenous methylprednisolone. We determined its effect on intragraft mRNA expression of immunoregulatory (interleukin-2, interleukin-4) and inflammatory cytokines (interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha), and the high-affinity interleukin-2 receptor (p55 chain) in endomyocardial biopsy specimens from cardiac allograft recipients. RESULTS: By reverse-transcriptase polymerase chain reaction methods, we detected mRNA transcription for interleukin-2 in 56% of the pretreatment endomyocardial biopsy specimens (n = 16), for interleukin-4 in 31%, and for interleukin-6 in 56% of the specimens, and interleukin-2 receptor, interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha were constitutively expressed. Individual cytokine mRNA profiles were not helpful in differentiating between rejections that proved to be methylprednisolone resistant (n = 9) or methylprednisolone sensitive (n = 7). After successful antirejection therapy, the overall intragraft mRNA expression was downregulated. None of the posttreatment endomyocardial biopsy specimens taken from six patients with methylprednisolone-sensitive rejections expressed the interleukin-2 gene, in contrast to 88% of the endomyocardial biopsy specimens obtained from eight patients with methylprednisolone-resistant rejections (p = 0.005). Moreover, intragraft interleukin-4 and interleukin-6 mRNA transcripts were hardly detectable (both 17%) in methylprednisolone-reversible rejections, but in ongoing rejections interleukin-4 mRNA expression was found in 62% (p = 0.14), and interleukin-6 was found in 88% of the endomyocardial biopsy specimens (p = 0.03). Semiquantitative analysis showed that the intragraft interleukin-2 receptor, interleukin-1 beta, and tumor necrosis factor-alpha mRNA levels were lower in posttreatment endomyocardial biopsy specimens from methylprednisolone-reversible rejections than in endomyocardial biopsy specimens from methylprednisolone-irreversible rejections (p = 0.03). CONCLUSIONS: Our data suggest that the efficacy of antirejection therapy with methylprednisolone is reflected in intragraft cytokine mRNA profiles.

Adolescent↗
PubMed1995

Prediction of improvement of regional left ventricular function after surgical revascularization. A comparison of low-dose dobutamine echocardiography with 201Tl single-photon emission computed tomography.

BACKGROUND: Although both 201Tl scintigraphy and low-dose dobutamine echocardiography (LDDE) have been proposed as effective methods of assessing myocardial viability, their relative efficacies are unknown. The aim of the present study was to compare the two imaging techniques in the prediction of improvement of regional left ventricular (LV) function after surgical revascularization. METHODS AND RESULTS: Thirty-eight patients with severe chronic LV dysfunction (ejection fraction < or = 40%, one or more akinetic [Ak] or severely hypokinetic [SH] segments on resting echocardiogram) who underwent uncomplicated coronary artery bypass graft surgery were studied with simultaneous dobutamine stress echocardiography and poststress reinjection 201Tl single-photon emission computed tomography (SPECT) before surgery. The Ak or SH segments were considered viable by LDDE when wall thickening improved during the infusion of 10 micrograms.kg-1 min 1 dobutamine. Scintigraphic definition of viability was the presence of normal 201Tl uptake, totally reversible defect, partially reversible defect, or moderately severe fixed defect. The postoperative improvement of dyssynergic segments was determined with a rest echocardiogram 3 months after surgery. Of 608 LV segments, 169 were classified as Ak and 51 as SH on resting preoperative echocardiography. Of these, 170 were successfully revascularized. Wall motion during LDDE improved in 33 severely dyssynergic segments and was more frequent in SH than in Ak segments (19 of 44 versus 14 of 126, P < .0001). Viability was detected by 201Tl SPECT criteria in 103 SH or Ak segments. Thirty-two of the 33 segments from LDDE responders were judged viable on 201Tl SPECT, whereas 201Tl viability was also detected in 71 of 137 segments from LDDE nonresponders. The sensitivity and the specificity for the prediction of postoperative improvement of segmental wall motion were 74% (95% confidence interval [CI], 67% to 81%) and 95% (95% CI, 92% to 98%) by LDDE and 89% (95% CI, 84% to 94%) and 48% (95% 40% to 56%) by 201Tl SPECT, respectively. Positive predictive value of LDDE was higher than that of 201Tl SPECT (85%, [95% CI, 80% to 90%] versus 33% [95% CI, 26% to 40%]). Thirty-six patients had angina before and only 1 had angina 3 months after revascularization. High-dose dobutamine echocardiography demonstrated significant reduction in stress-induced ischemia (new or worsening of preexisting wall motion abnormalities) after surgery (from 163 to 23 LV segments). CONCLUSIONS: In patients with severe chronic LV dysfunction, LDDE is a good predictor of the improvement of dyssynergic segments after revascularization. Because 201Tl SPECT overestimates the probability of postoperative improvement of dyssynergic segments, LDDE should be the preferred imaging technique for preoperative assessment of these patients.

Coronary Artery Bypass↗