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F H Claas

Publications and source records attributed to F H Claas.

At least 145 records · Page 8Linked to original sources
PubMed1993

Donor heart endothelial cells as targets for graft infiltrating lymphocytes after clinical cardiac transplantation.

The in vitro cytotoxic reactivity of allograft infiltrating cells cultured from endomyocardial biopsies was tested against endothelial cells (EC) isolated from the own donor heart. EC derived from pieces of atrium were found to be proper targets for graft infiltrating cytotoxic T cells from four patients. The specificity of this cytotoxicity was further analysed by cold target inhibition studies and blocking with anti-CD3, anti-CD4 or anti-CD8 monoclonal antibodies. The experiments revealed that, besides a clearly HLA directed recognition, a more heterogeneous, multispecific response can be found, which might be partially explained by the activity of EC specific T cell clones. We conclude that this system provides a valuable approach to investigate the reactivity of graft infiltrating cells against EC in relation to the clinical course of the transplantation.

Antibodies, Monoclonal↗
PubMed1993

Altered specificity of alloreactive cardiac graft-infiltrating cells by prophylactic treatment with OKT3 or horse antilymphocyte globulin.

Graft-infiltrating lymphocytes from patients who were prophylactically treated with OKT3 or horse antilymphocyte globulin (H-ALG) were found to have different specificity patterns from those in the control group that received cyclosporine from the day of transplantation. This prophylactic treatment led to a significant decrease of the HLA-DR-directed cytotoxicity, while the cytolytic response against HLA-class I mismatches was hardly affected. In H-ALG patients without rejection, the percentages of class I-reactive cultures were found to be lower than in the other treatment groups, which was mainly due to a lower percentage of HLA-B--reactive cultures. In CsA and OKT3 patients, cytotoxic T cells were rather directed to HLA-B mismatches than to HLA-A antigens, while in H-ALG patients no difference in HLA-A and B-directed cytotoxicity was found. Our data suggest that OKT3 and H-ALG influence the specificity of the T cell allorepertoire, resulting in a decreased frequency of class II-specific cytotoxic T cells after transplantation. H-ALG also has a downregulating influence on the CTL response against HLA class I (HLA-B) antigens. In some patients a fast regeneration of these cells occurs, which results in a higher rejection incidence during the first posttransplant year.

Antilymphocyte Serum↗
PubMed1993

Differential inhibition of primed alloreactive CTLs in vitro by clinically used concentrations of cyclosporine and FK506.

Previous studies in highly sensitized patients waiting for a renal transplant showed a lack of correlation between the formation of alloantibodies and the alloantigen specific cytotoxic T cell precursor frequency. The frequencies of CTLp against HLA class I antigens, toward which patients had formed antibodies (not acceptable mismatches, NAM), were similar to those against HLA antigens, toward which no antibodies were present (acceptable mismatches, AM). In more recent studies we tested whether the immunological triggering leading to antibody formation might have resulted in a different population of cytotoxic T cells. Limiting dilution assays performed in the absence or presence of antibodies against CD8 showed that CTL directed against NAM were significantly less inhibited by anti-CD8 compared with those directed against AM. Those "primed" CTL could also be distinguished from the more "naive" CTL on the basis of their resistance to cyclosporine. In contrast to CsA, therapeutic concentrations of FK506 were able to inhibit both "naive" and "primed" CTLs. The clinical relevance of these data is currently being investigated.

Cyclosporine↗
PubMed1993

The detection of cytotoxic T cells with high-affinity receptors for donor antigens in the transplanted heart as a prognostic factor for graft rejection.

Alloreactive T lymphocytes are the initiators and effectors of acute rejection of organ transplants, and T cells with high-affinity receptors for antigen might be especially implicated in this process. It has been shown that the cytotoxic capacity of CTL with low affinity for alloantigens can be inhibited with CD8 mAb, while high-affinity CTL are not affected. To investigate whether the presence of such high-affinity cells in human heart transplants may be predictive for acute rejection, we analyzed their frequency in cultures derived from endomyocardial biopsies in 19 patients, 9 of whom had never experienced acute rejection and 10 who had had one or more rejection episodes. IN the rejectors, already before histological signs of rejection (myocyte damage) had developed, significantly higher donor-reactive CTL frequencies were found compared with the nonrejectors (medians of 10,586 vs 1,169 reactive cells per 10(6) tested cells, P = 0.002). After CD8 inhibition, the difference between rejectors and nonrejectors was even more pronounced (P < 0.001). In patients with rejection, the number of CD8-resistant, high-affinity CTL was higher than 1000 per million cells in all cases, while in patients who had never experienced rejection this number was less than 1000. As these CTL characteristics are already present before the first histological signs of rejection have developed, this might be used as a prognostic factors.

Antibodies, Monoclonal↗
PubMed1993

Sunlight, keratotic skin lesions and skin cancer in renal transplant recipients.

In a retrospective follow-up study, 36 renal transplant recipients with, and 101 without, skin cancer, who had received their first transplant before January 1981 and who were still alive with a functioning graft on 1 August 1989, were assessed to determine the risk of non-melanoma skin cancer in relation to exposure to sunlight during childhood and adolescence. The contribution of the number of keratotic skin lesions to the skin cancer risk was also assessed. The estimated relative risks (odds ratios) of skin cancer in relation to exposure to sunlight and the presence of keratotic skin lesions were calculated by maximum likelihood estimation in a logistic model. The majority of skin cancers and keratotic skin lesions were confined to sun-exposed skin. After adjustment for possible confounding variables, the odds ratios of skin cancer for moderate and high cumulative life-time exposure to sunlight, respectively, compared with low exposure, were 2.4 (95% confidence interval [CI] 0.64-9.3) and 47.6 (95% CI 5.4-418). Exposure to sunlight before the age of 30 contributed more to the risk of developing skin cancer later in life than exposure after the age of 30. No association was found between cumulative life-time exposure to sunlight and the number of keratotic skin lesions. Nevertheless, these lesions behaved as a strong independent risk factor in the development of skin cancer. The adjusted odds ratio of skin cancer for 50-99 lesions compared with < 50 lesions was 4.5 (95% CI 1.1-18.2); the adjusted odds ratio for > or = 100 lesions compared with < 50 lesions was 20.8 (95% CI 5.3-81.7).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Laboratory procedures used to select an unrelated HLA matched bone marrow donor.

Selecting an HLA matched unrelated bone marrow donor is a labour-intensive step-by-step procedure, with highly specialized techniques. To be successful immunohematologists and clinicians have to work closely together. Because so much is still unknown lymphocytes and serum of patient and donor should be stored to enable future analyses.

Bone Marrow Transplantation↗
PubMed1992

Lysis of heart endothelial cells from donor origin by cardiac graft infiltrating cells.

Endothelial cells may be involved in the acute rejection of allografts. In the present study, graft infiltrating lymphoid cell lines were propagated from a heart graft at the time of histological diagnosis of rejection. The cell lines containing CD8+ cells lysed donor-derived BLCL and endothelial cells (EC) but not third party BLCL or random EC, suggesting that HLA antigens were recognized. The cell lines containing CD4+ cells only did not lyse any target cells. The lysis of EC without preincubation with gamma interferon (gIFN) indicated that the HLA antigens recognized were class I antigens. These results suggested that lysis of donor EC may be one of the mechanisms involved in rejection.

CD4-Positive T-Lymphocytes↗
PubMed1992

The influence of HLA-mismatches on phenotypic and functional characteristics of graft infiltrating lymphocytes after heart transplantation.

We studied the influence of HLA mismatches on T lymphocyte cultures that were derived from endomyocardial biopsies (EMB) from 118 heart transplant recipients. From patients with DR mismatches, the majority of the EMB-derived cultures were dominated by CD4, while in patients without DR mismatches, CD8 was the predominant T cell subset. The majority (75%) of the cultures were cytotoxic against donor antigens. A significantly (P < 0.005) lower proportion of the cultures showed cytotoxicity (36%) against HLA-A antigens when compared to HLA-B (53%) or HLA-DR (49%). A dose effect phenomenon was detected for all HLA antigens, including HLA-A: a higher number of A, B or DR mismatches resulted in a higher number of cytotoxic cultures directed against these antigens. B and DR matching had the greatest influence on 6 month freedom from rejection. Both our experimental and clinical data indicated that HLA matching played a role in the immune response against a transplanted heart.

Biopsy↗
PubMed1992

Monitoring of cardiac graft recipients: comparison of in vivo activated, committed T lymphocytes in peripheral blood and in the graft.

The proliferative and cytotoxic capacity of peripheral blood lymphocytes (PBL) and the cytotoxic activity of lymphocytes propagated from endomyocardial biopsies (EMB) towards donor cells was used to identify in vivo activated, committed T cells. A series of 39 PBL samples and 38 EMB simultaneously taken from 20 patients after heart transplantation was cultured in interleukin 2 (IL-2) conditioned medium. The cytotoxic capacity of these cultures against donor cells was tested in a 4-h chromium-51 release assay. From a comparable patient group, 224 samples were evaluated for donor reactivity by a primed lymphocyte test (PLT). Analysis showed that PBL cultures hardly ever contained committed cytotoxic T lymphocytes (cCTL, 2/39) or committed proliferative T lymphocytes (cPTL, 1/224). In contrast, significantly more EMB cultures (17/38, P < 0.001, chi2 test) demonstrated donor-directed cytotoxicity. This was especially found during rejection (11/17 vs 6/21 without rejection, P = 0.05). These results show that after heart transplantation, committed cells are mainly found in the graft.

Cell Culture Techniques↗
PubMed1992

The amplifier role of T cells in the human in vitro B cell response to type 4 pneumococcal polysaccharide.

The human B cell response to T cell independent type 2 antigens is regulated by thymus-derived lymphocytes. We analyzed the role of T cells in the in vitro antibody response to type 4 pneumococcal polysaccharide (PS4). We here show that the amplifying effect of T cells, which has previously been shown to be radioresistant and confined to T cell preparations enriched for CD4+ cells, is MHC non-restricted as demonstrated in cultures carried out in the presence of allogeneic T cells. Also, T cell clones derived from non-related donors are able to enhance the B cell response to PS4. All TCR alpha beta +, CD 4+ T cell clones, but none of the TCR alpha beta +, CD 8+ T cell clones tested, enhanced the B cell response to PS4. Furthermore, 3 out of 6 TCR gamma delta+ T cell clones were capable of enhancing the anti-PS4 B cell response. Experiments using recombinant lymphokines and glutaraldehyde-fixed T cells indicated that both lymphokines and T-B cell interactions are required for an optimal antibody response to PS4.

Antibodies↗
PubMed1992

Determination of cytotoxic T-lymphocyte precursor frequencies using europium labeling as a nonradioactive alternative to labeling with chromium-51.

We report on the use of europium (Eu) as a suitable nonradioactive alternative for target cell labeling in limiting dilution analysis (LDA) assays set up to determine cytotoxic T-lymphocyte precursor (CTLp) frequencies. A nonradioactive alternative to the commonly used chromium-51 (51Cr) release assay seems desirable because working with radioisotopes has some major disadvantages concerning possible health risks, environmental load, costs of facilities necessary for working with radioisotopes, and shelf life. Some groups have successfully applied the Eu release assay based on detection by time-resolved fluorometry, to tests in which NK- or LAK-cell activity or cytotoxic T-lymphocyte reactions were measured. This led to the investigation whether this method could also be applicable to the more specific determination of CTLp frequencies in LDA assays. After optimal labeling conditions had been established, the sensitivity of the Eu release assay was determined by performing several LDA assays in which the target cells were labeled with either Eu or radioactive 51Cr. When CTLp frequencies were compared, it was shown that the Eu release assay is at least as sensitive and specific as the 51Cr release assay. Moreover, although the labeling procedure takes longer, sample processing is much faster: only 1 second per sample. The fact that the Eu release assay is not radioactive enables the assay to be performed at any laboratory and even--because the frequency of CTLps may have implications for organ graft survival and for donor selection in bone marrow transplantation--to do so on a routine basis.

Cell Count↗
PubMed1992

Acute rejection in heart transplant patients is associated with the presence of committed donor-specific cytotoxic lymphocytes in the graft but not in the blood.

In vivo-activated, committed donor-specific cytotoxic lymphocytes (cCTL) can be propagated and expanded from endomyocardial biopsies (EMB) in IL-2-enriched medium especially during an acute rejection episode. We report here our efforts to detect these cCTL by the same technique in peripheral blood at the moment of rejection and when no rejection was diagnosed. During or just before rejection, significantly less frequent (P less than 0.01) donor reactive cCTL were found in PBL samples (two out of 20) than in the simultaneously taken EMB samples (13 out of 19). Donor B-LCL and/or third-party B-LCL were lysed by 15 PBL samples. Inhibition studies revealed that this lysis was due to LAK-like cytotoxicity. The results show that peripheral blood does not reflect intra-graft events, which is probably the reason for the irreproducible results of diagnosis of rejection by monitoring immunological parameters in the peripheral blood.

Biopsy↗