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Biomedical subjects

L M Vaessen

Publications and source records attributed to L M Vaessen.

At least 37 records · Page 2Linked to original sources
PubMed1998

Kinetics of circulating cytotoxic T lymphocyte precursors that have a high avidity for donor antigens: correlation with the rejection status of the human cardiac allograft.

Studies on graft infiltrating cells demonstrated that accumulation of cytotoxic T lymphocytes (CTL) with high avidity for donor antigens (Ag) coincided with acute cardiac rejection. In the present study, we analyse whether such high-avidity CTL are present within the peripheral blood of cardiac transplant recipients and whether their kinetics correspond with the rejection status of the allograft. Using limiting dilution analysis (LDA), donor-specific CTL were enumerated in serial blood samples of seven patients. From each patient, 7-11 samples were obtained during the first year after transplantation and up to three samples were obtained at a later date. Enumerated donor-specific CTL were divided into CTL with high or low avidity for donor Ag, depending on their sensitivity to CD8-blocking. In contrast to the situation in the graft, the donor-specific CTL present within the peripheral blood were CTL precursors (pCTL) and not fully mature CTL (cCTL). The number of donor-specific pCTL among peripheral blood cells fluctuated irrespective of the rejection grade of the allograft, indicating that the frequency of circulating donor-specific CTL does not reflect the immunological status of the allograft. During acute cardiac rejection, 66% (median) of the circulating donor-specific pCTL had a high avidity for donor Ag. This percentage significantly exceeded pre- and postrejection values obtained during the first year post-transplantation (median, 39% and 37%, respectively). The disparity in avidity increased even further more than 1 year after transplantation, when stable engraftment was achieved. Among donor-specific pCTL in peripheral blood, those with a high avidity were absent (median, 0%). Hence the avidity of circulating donor-specific CTL might inform us about the immune status of the cardiac allograft.

Antigens↗
PubMed1998

The frequency and avidity of committed cytotoxic T lymphocytes (cCTL) for donor HLA class I and class II antigens and their relation with graft vascular disease.

Cellular immune processes may trigger the development of graft vascular disease (GVD). CD4 and CD8 cytotoxic T lymphocytes that infiltrate the allograft could play a role in the development of GVD. We studied the presence of in vivo primed or committed CTL (cCTL) and their avidity for donor HLA class I and class II antigens in graft-infiltrating lymphocyte cultures propagated from endomyocardial biopsies derived from patients with and without signs of GVD. The fraction of cCTL with high avidity for HLA class I or class II antigens was estimated by the addition of anti-CD8 or anti-CD4 MoAbs to the cytotoxic phase of the limiting dilution analysis. In the first year after transplantation no difference in the frequency of donor-specific class I cCTL between patients with and without GVD was found. Addition of anti-CD8 MoAb revealed that most cultures predominantly consisted of cCTL with low avidity for donor HLA class I antigens, irrespective of the development of GVD at 1 year after transplantation. However, in patients who did not develop GVD, the frequency of cCTL with donor HLA class II specificity was significantly higher than in patients who did develop GVD. The avidity for donor HLA class II antigens was comparable in both groups. A high frequency of donor-specific cCTL for HLA class II antigens seems to be a protective factor against the development of GVD. These cCTL might be cytotoxic for cells involved in GVD development, e.g. activated endothelium and smooth muscle cells of donor origin.

Antibodies, Monoclonal↗
PubMed1997

Donor-specific cytokine production by graft-infiltrating lymphocytes induces and maintains graft vascular disease in human cardiac allografts.

BACKGROUND: The development of graft vascular disease (GVD) in the allograft is a major impediment for long-term survival of heart transplant recipients. GVD may be mediated by cellular processes, in response to the transplanted heart, and regulated by cytokines. METHODS: We studied donor-specific cytokine production patterns in graft-infiltrating lymphocyte cultures propagated from endomyocardial biopsies. The biopsies were derived from patients with and without signs of GVD, as diagnosed by angiography at 1 year after heart transplantation. RESULTS: In the first year after transplantation, significantly more T-helper (Th) 1 cytokines (interleukin [IL]-2: P=0.04; interferon-gamma: P=0.01), but not Th2 (IL-4 and IL-6) cytokines, were produced by cultures of patients with GVD compared with patients without GVD. Thereafter, the Th1 cytokine levels in patients with GVD normalized to the levels of patients without GVD. Detectable levels of IL-6 were produced significantly more often (P=0.009) by cultures obtained more than 1 year after transplantation from patients with GVD. CONCLUSIONS: The results suggest that high levels of Th1 cytokines produced by graft-infiltrating lymphocytes early after transplantation may be responsible for activation of vascular endothelium, leading to the migration and proliferation of smooth muscle cells that is characteristic of GVD. IL-6, produced later after transplantation, continues this process by promoting smooth muscle cell proliferation.

Cells, Cultured↗
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

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

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

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

Inverted V delta 1/V delta 2 ratio within the T cell receptor (TCR)-gamma delta T cell population in peripheral blood of heart transplant recipients.

We investigated the levels of TCR-gamma delta T cells and their subpopulations V delta 1 and V delta 2 in the peripheral blood lymphocytes (PBL) of 28 heart transplant (HTx) patients. Patients (n = 10) receiving cyclosporin A (CsA) for treatment of a nephrotic syndrome (NS) and 10 healthy individuals served as controls. There was no difference in levels of TCR-gamma delta T cells between the different groups. However, an elevated proportion of V delta 1+ gamma delta T cells was found in the PBL of HTx patients, especially when these cells were present in their graft-infiltrating lymphocyte (GIL) cultures. V delta 1+ gamma delta T cells of HTx patients showed normal expression of CD45RO and lacked the activation markers CD25 and HLA-DR. After expanding in IL-2-containing medium, PBL cultures of HTx patients more often were dominated by V delta 1 cells than PBL cultures of controls, in which V delta 2 cells were predominantly grown. The aberrant composition of the TCR-gamma delta population in HTx patients was not a result of immunosuppressive medication, since the proportion V delta 1+ gamma delta T cells was normal in the PBL of the NS patients receiving a similar dose of CsA. It is postulated that long-term antigenic stimulation by the graft, at low level, might be responsible for the altered composition of the gamma delta pool in the HTx patients. Since no donor HLA-specific gamma delta T cells have been detected, other ligands, such as heat shock proteins, may be involved.

Adolescent↗
PubMed1995

A double-blind, placebo-controlled study of monoclonal anti-interleukin-2 receptor antibody (BT563) administration to prevent acute rejection after kidney transplantation.

In a double-blind, randomized, placebo-controlled trial, BT563, a murine IgG1 anti-IL-2R antibody, was given as a rejection prophylaxis after kidney transplantation. Drug-related side effects were not observed. During the 10-day course of BT563, no rejections (0/27) were found, whereas a rejection episode occurred in 7 patients (7/29) (P = 0.01) during placebo treatment. Within the first 4 postoperative weeks, freedom from rejection in the BT563 group and in the placebo group was 96% vs. 76% (P = 0.05). Due to rejection in the placebo group, 2 grafts were lost. At 3 months, an overall rejection incidence in the BT563 and placebo group was found of 3/27 (11%) vs. 8/29 (28%) patients (P = 0.18). Infectious complications were distributed equally between the 2 groups. CMV disease, found in 3 placebo-treated patients, occurred after rejection treatment (2/3). Within the BT563 group, 1 patient lost his graft due to renal artery thrombosis, 2 grafts were lost as a result of technical failure, and 2 patients had a squamous cell carcinoma that could be treated curatively. We conclude that the use of the anti-IL-2R mAb BT563 effectively prevents rejection after kidney transplantation without increasing infectious complications.

Acute Disease↗
PubMed1995

Soluble tumor necrosis factor-receptors are not a useful marker of acute allograft rejection: a study in patients with renal or cardiac allografts.

In this study, we investigated soluble tumor necrosis factor receptor (sTNF-R) levels in plasma of patients with either a kidney or cardiac allograft when clinical suspicion of acute rejection was raised. In plasma of patients with acute renal graft rejection, the sTNF-R levels were strongly enhanced (20-150 ng/ml) as compared to plasma of patients with stable renal function. Following successful treatment of the rejection, a gradual decline in sTNF-R levels occurred with improving renal function, and an inverse correlation between creatinine clearance and sTNF-R was found. To determine whether the increase was caused by an accumulation of constitutively released sTNF-R and lack of clearance by the kidney, or whether the immunological process of the rejection caused the enhancement, we measured sTNF-R in patients suffering from acute cardiac graft rejection but with predominantly stable kidney function. Rejection of a cardiac graft did not lead to a significant enhancement of sTNF-R levels. However, treatment with ATG or OKT3 did cause enhanced sTNF-R levels, followed by a decline that reached starting values after 7 days. These results provide evidence that the immune reaction that occurs during rejection of a graft does not per se induce discernible changes in sTNF-R levels, whereas that induced by ATG or OKT3 does. Thus, sTNF-R levels are not reliable marker in transplant recipient monitoring.

Acute Disease↗
PubMed1995

Pharmacodynamics of prophylactic antirejection therapy with an anti interleukin-2 receptor monoclonal antibody (BT563) after heart and kidney transplantation.

A mouse monoclonal antibody (BT563) directed to the alpha-chain of the IL-2 receptor was administrated immediately after transplantation in a dose of 10 mg/day prophylactically to 30 heart transplant recipients (HTx) and 40 renal transplant recipients (RTx) to induce immunosuppression. Plasma levels increased to a plateau level of 5300 ng/ml in HTx and 5900 ng/ml in RTx. BT563 plasma disappearance curves gives a mean T1/2 of respectively 39 h (range 14-112 h) and 42 h (range 8-122 h) for HTx and RTx respectively. The CD25 marker (IL-2R) on the peripheral blood lymphocytes disappeared within hours after the first gift and returned to normal within 0-20 days after the last gift. In HTx more often CD25+ cells were found in the presence of BT563 and more rejections occurred shortly after discontinuation of BT563 compared to the RTx group. Rejectors and non-rejectors within the HTX group did not differ with respect to the period of depletion of CD25 positive cells in the peripheral blood. In 56% of the patients a substantial IgM antibody response was detected. This response was similar for HTx and RTx and not related to rejection. The frequency of IgG responses was low in both HTx (13%) and RTx (21%) patients and the IgG response was not related with graft rejection or with antirejection treatment. Peripheral monitoring showed that mAb plasma levels, antimurine antibody responses and number of CD25 positive cells were not related with the clinical results. The mAb BT563 proved to be safe with respect to the generation of antimurine antibodies and, when given in combination with CsA, is a therapy with a potential for high efficacy.

Animals↗
PubMed1995

Production and characterization of monoclonal and polyclonal antibodies against thyrotropin-releasing hormone.

In this article, two mouse monoclonal antibodies (83-7B5-A1 and 83-6B6-A10) and three rabbit polyclonal antibodies (1118, 8572, and 8577) directed against thyrotropin-releasing hormone (TRH; pGlu-His-Pro-NH2) are described. The anti-TRH antibodies were raised by immunization with a TRH-bovine serum albumin conjugate obtained by coupling of the CO2H group of pGlu-His-Pro-OH to NH2 groups in the protein. The monoclonal antibodies were produced by hybridoma clones obtained by the fusion of SP2/0 myeloma cells with spleen cells of an immunized BALB/c mouse. Both monoclonal antibodies were of the IgG1 (kappa) subclass. Characterization of the anti-TRH antibodies showed that in general they are specific for the pGlu-His moiety. The cross-reactivities for the TRH-like peptides [Glu1]TRH, [Glu2]TRH, and [Phe2]TRH are low, while alterations at the Pro-NH2 moiety of TRH are recognized to varying extents. The specificities of these antibodies are markedly different from those previously obtained using TRH coupled through the histidine residue to protein as the immunogen.

Amino Acid Sequence↗