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Biomedical subjects

H M Gebel

Publications and source records attributed to H M Gebel.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of peripheral blood CD8/11b cells in bone marrow transplant recipients. III. Subsets of CD8/11b cells differentially regulate immunoglobulin production.

Recovering bone marrow transplant (BMT) recipients have 20-70% circulating lymphocytes which co-express CD8 and CD11b (normals = 5-15%). These CD8/11b cells comprise at least two subpopulations distinguished by their expression of CD3. The CD3+ CD8/11b cells are T lymphocytes which exhibit in vitro suppressor activity (Ts); the CD3- CD8/11b cells express CD16 and are natural killer (NK) cells. In this study, we investigated whether such cells influenced circulating levels of IgA and IgM in 18 BMT recipients who each had greater than 30% circulating CD8/11b cells. We observed that in all patients whose CD8/11b cells were Ts lymphocytes (7/7) IgM and IgA levels were less than 10% of normal. Among those patients whose CD8/11b cells were NK cells (n = 11), two groups were distinguished. In one group (n = 5), less than 35% of patient NK cells expressed CD57 and serum levels of IgM and IgA were less than 10% of normal. In the second group (n = 6) greater than 60% of the NK cells expressed CD57 and serum levels of IgM and IgA were normal. In summary, our data indicate that BMT recipients have at least three distinct subsets of CD8/11b lymphocyte populations which may differentially regulate IgM and IgA production in vivo.

Adolescent↗
PubMed1991

Detection of cytotoxic T lymphocytes specific for synthetic peptides of gp160 in HIV-seropositive individuals.

Four synthetic peptides corresponding to the IIIB sequence of gp160 of HIV were recently reported to stimulate Th cell function by PBL from HIV-infected, asymptomatic patients. In the present report, we used these same peptides to demonstrate CTL activity in a similar patient population. EBV-transformed B-cell lines from asymptomatic, HIV seropositive and seronegative control donors were pre-incubated with the peptides. Fresh PBL from 19 (76%) of 25 HIV seropositive donors lysed autologous targets pulsed with at least one of the four peptides. Autologous targets pulsed with two non-immunogenic peptides were not lysed. PBL from none of the eight HIV seronegative controls lysed peptide-preincubated autologous targets. The CTL activity was mediated by T cells, was predominantly MHC class I restricted, and was increased by in vitro restimulation of PBL with the peptides. HLA A-2 was identified as a restricting element for all four peptides in different patients, and for three of the peptides in the same donor. HLA-A1 or -B8 may also present some of the peptides. Thus, the same peptides can be recognized by human Th cells and class I MHC-restricted CTL.

Cytotoxicity, Immunologic↗
PubMed1991

Multidrug resistance activity in human lymphocytes.

The multidrug resistance gene (mdr1) is a member of the recently described ATP binding cassette (ABC) superfamily of transporters. Family members include: (1) the cystic fibrosis transmembrane conductance regulator gene; (2) the hlyB gene of bacteria, and (3) the histocompatibility antigen modifier (HAM) gene. The level of expression of mdr1 correlates with multidrug resistance (MDR), the ability of cells to efflux otherwise toxic doses of several chemotherapeutic agents. MDR activity is also associated with the efflux of cationic lipophilic compounds such as the fluorescent dye rhodamine 123. Recently it was reported that normal lymphocytes efflux rhodamine 123, suggesting that these cells possess MDR-like activity due to the expression of mdr1. In this study, using two-color flow cytometric analysis, we observed that the ability to efflux rhodamine 123 was heterogeneous among human lymphocyte subsets in the order of CD8 greater than CD4 greater than CD2O. Rhodamine 123 efflux and accumulation in lymphocytes was sensitive to the known MDR reversing agents, verapamil and Solutol HS 15. Collectively, these data suggest that an MDR-like transport system is present in normal lymphocytes and may be important for trafficking of molecules involved in lymphocyte function.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Crossmatch procedures used in organ transplantation.

Several lymphocyte crossmatch procedures used in clinical histocompatibility laboratories, including complement dependent (CDC, AHG-CDC) and complement independent (flow cytometric, chromium release) techniques, are used to assess the likelihood of allograft rejection due to preformed donor specific antibody. Crossmatch assays can be extremely sensitive and detect very low levels of donor reactive antibody present in the potential recipient. Since positive crossmatches are usually associated with allograft rejection, a positive crossmatch is generally a contraindication to organ transplantation. Recent data, however, suggests that not all positive crossmatches lead to graft rejection, particularly those due to autoantibodies. This underscores the need to critically evaluate any positive crossmatch to determine if the antibodies involved in the reaction are relevant to allograft rejection.

Chromium Radioisotopes↗
PubMed1990

Two populations of CD56 (Leu-19)+/CD16+ cells in bone marrow transplant recipients.

Bone marrow transplant (BMT) recipients are severely immunocompromised during the early post-transplant period as their immune systems recapitulate. Among the first cells to repopulate the peripheral blood are natural killer (NK) cells. Studies in normal subjects have revealed that the majority of NK cells express CD16 and CD56 (Leu-19). Such NK cells express low density, dim, Leu-19 (Leu-19D+). A small percentage of high-density, bright, Leu-19 cells (Leu-19B+) which are CD16- have also been reported in normal subjects. In this study we observed that peripheral blood mononuclear cells (PBMC) from BMT recipients contained two distinct populations of Leu-19+ cells that co-expressed CD16 and these populations could be separated on the basis of differential Leu-19 and CD16 fluorescence intensities. Leu-19B/CD16D and Leu-19D/CD-16B cells were present in four of nine BMT patients studied. Cells from one BMT recipient with a very large expansion of the Leu-19B+ population (46% of PBMC by flow cytometry) were studied in detail. While this patient is not characteristic of all BMT recipients, the large number of Leu-19+ cells that could be isolated from him allowed extensive analysis of a previously unreported population of cells. Our data suggest that BMT recipients can be an important group of subjects to evaluate NK cell subsets as these cells mature and, presumably, differentiate in a regenerating immune system.

Adolescent↗
PubMed1989

T cells from patients successfully treated with OKT3 do not react with the T-cell receptor antibody.

The mechanism of OKT3 therapy is complex and may include depletion of circulating CD3 cells, modulation of the CD3 molecule, and/or functional inactivation of T cells. Although the absolute number of circulating CD3 cells in OKT3-treated patients is used to monitor therapy, many laboratories assign CD3 numbers based on reactivity with OKT3. These CD3 numbers could be artificially low since the epitope recognized by OKT3 may already be occupied. Using a monoclonal antibody against a different CD3 epitope, we detected CD3 expression on T lymphocytes from 18/18 OKT3-treated patients. Nonetheless, OKT3 therapy in these patients was clinically successful, suggesting that monitoring patients solely for CD3 is uninformative. Since CD3 is associated with the T-cell receptor (TcR), we also evaluated alpha-TcR-1, a monoclonal antibody which detects a conformational determinant of the CD3/TcR alpha/beta complex, and found that less than 1% of the CD3 cells from OKT3-treated patients reacted. Furthermore, these cells were unresponsive to allogeneic stimulation. However, when patient cells were cultured overnight in the absence of OKT3, both alpha-TcR 1 binding and responsiveness to allogeneic stimulation became detectable. Thus, the monitoring of patients treated with OKT3 can be more informative if lymphocytes are tested for reactivity with alpha-TcR-1 and an alpha-CD3 antibody other than OKT3.

Antibodies, Monoclonal↗
PubMed1989

Immunologic aspects of endometriosis.

Endometriosis appears to be a systemic disease with alterations in both humoral and cell-mediated immunity. An immune defect may allow ectopic implantation of the endometrial cells with subsequent development of autoantibodies.

Endometriosis↗
PubMed1989

The flow cytometric crossmatch. Dual-color analysis of T cell and B cell reactivities.

The flow cytometric crossmatch (FCXM) has become an increasingly utilized method to detect low levels of anti-donor antibodies (e.g., anti-HLA) in potential renal allograft recipients. Anti-donor antibodies not apparent in the standard complement-dependent crossmatch, but detectable by the FCXM, are often associated with increased episodes of graft rejection and early graft failure. In this study we examined several parameters of the FCXM in order to establish a standardized methodology. First, we observed that optimal staining results were obtained when the secondary antibody was an Fc-specific F(ab'), anti-human IgG. In contrast to an anti-whole immunoglobulin antibody, the anti-Fc specific reagent did not react with surface immunoglobulin on B cells but was reactive with cytophilic immunoglobulin present on CD16+ cells. Next we determined that dualcolor analysis was superior to single-color analysis both for the evaluation of T cell reactivities and for the discrimination of T cell from B cell reactivities. Additionally, dual-color analysis revealed that the density of class I histocompatibility antigens on B cells is greater than on T cells, indicating that B cells may be a more sensitive target for detecting low levels of anti-class I antibodies. Finally, we determined that a shift in the mean fluorescence intensity of greater than 10 channels on a 256-channel, 3-decade log scale was indicative of a positive FCXM. The data presented in these studies provide the basis for performing standardized dual-color FCXM with increased sensitivity and specificity.

B-Lymphocytes↗
PubMed1988

The characterization of Ia+ cells in human parathyroid and islets.

Recent studies in animals have shown prolonged survival of endocrine allografts after treatment of the graft with Ia antibody prior to transplant. In this study, we documented the presence of Ia bearing passenger cells in human parathyroid and islets of Langerhans. Furthermore, we characterized these cells with regard to their expression of HLA-DQ and HLA-DR molecules using indirect immunofluorescence. We found that passenger cells in parathyroid express both HLA-DQ and HLA-DR. In contrast, islets express only HLA-DR. Parathyroid tissue treated first with polyclonal anti-DR or anti-DQ and complement eliminated cells that reacted with monoclonal anti-DR or -DQ probes, respectively. Similarly, islets treated with polyclonal anti-DR and complement eliminated cells that reacted with monoclonal anti-DR reagents. We believe that further characterization of Ia+ cells in human endocrine tissue will provide information that could be used to enhance allograft survival.

Cytotoxicity Tests, Immunologic↗
PubMed1988

Characterization of peripheral blood CD8/11 cells in bone marrow transplant recipients. II. Two distinct populations of CD8/11 cells.

Flow cytometric analysis of mononuclear cell surface antigens identified 2 distinct populations of CD8/11 cells in the peripheral blood of recovering bone marrow transplant (BMT) recipients. These populations were distinguished based on differential CD8 antigen expression. One population expressed high-surface density CD8 (CD8 bright/11); the other population expressed low-surface density CD8 (CD8 dim/11). The surface expression of CD11, the C3bi receptor on lymphocytes, is similar in CD8 right/11 and CD8 dim cells. Thus, although 13 BMT recipients had elevated CD8/11 cells (mean = 27% +/- 9%; normal range mean = 7.4 +/- 3.3%), the percent of CD8 bright/11 cells versus CD8 dim/11 cells varied. The majority of cells in patients with a predominant CD8 right/11 phenotype did not express CD16 (Fc gamma receptor). In contrast, the CD8 dim/11 cells coexpressed CD16. When functional studies were performed, we observed high numbers of CD8 right/11 cells correlated with low natural killer (NK) lytic activity, while patients with less than 25% CD bright/11 cells had high NK activity. Analysis of interleukin 2 (IL-2) production revealed that none of the peripheral blood mononuclear cells (PBMC) from BMT patients synthesized IL-2 at less than 1.5 months posttransplant. However, cells from some patients began to synthesize IL-2 at approximately 2 months posttransplant. It is likely that both populations of CD8/11 cells have an impact on the regeneration and regulation of the immune system in BMT recipients.

Antigens, Differentiation↗
PubMed1987

New method for cardiac transplantation.

Rat cardiac transplantation into the femoral region has several advantages compared to cardiac transplantation into the peritoneal cavity. These advantages include increased speed, decreased hypothermia of the recipient, and easier-access palpation. However, there is a major discrepancy in the size of the donor and recipient vessels. The donor aorta is two to three times larger than the recipient's femoral artery and thus could be a contraindication to the transplant. To circumvent this problem, we anastomosed the donor's aorta with the recipient's femoral artery by an end-in-end technique whereas the donor's pulmonary artery was anastomosed by conventional end-to-end technique with the recipient's femoral vein. The excess wall of the donor's vessel was plicated on a slant for each anastomosis. Our results compare favorably to those of techniques established previously. We suggest that this new method of cardiac transplantation will be of great value in the study of immunological events involved in graft rejection.

Anastomosis, Surgical↗
PubMed1987

Differential surface marker expression in patients with CD-16+ lymphoproliferative disorders: in vivo model for NK differentiation.

In this study, we report on three patients, each with a CD-16+ lymphoproliferative disorder. Peripheral blood lymphocyte from all three patients were evaluated for lymphocyte morphology, natural killer (NK) function, and surface marker expression. In addition, two-color flow cytometric analysis was performed to determine the phenotype of the CD-16+ cells. Our findings indicate that the presence of increased numbers of CD-16+ cells alone is not a good predictor of NK activity. However, we observed a differential expression of the HLA class II molecules DR and DQ on the CD-16+ cells obtained from these patients that was associated with NK function. Hence, a CD-16+, Leu-7-, Leu-19+ (NKH-1A) and HLA class II+ phenotype did correlate with NK function in contrast to a CD-16+, Leu-7+, Leu-19- (NKH-1A) and HLA class II- phenotype. Of importance was the fact that the CD-16+, HLA class II+ cells did not express CD-25 or TFR, nor did they mediate cytotoxicity against solid tumor targets, suggesting that these CD-16+ cells are not activated. Thus, in contrast to previous studies of NK ontogeny that utilized in vitro activated NK cells, studies of patients with CD-16+ lymphoproliferative disorders may provide an alternative approach for examining NK differentiation.

Adult↗
PubMed1987

Characterization of circulating suppressor T lymphocytes in bone marrow transplant recipients.

Peripheral blood T lymphocytes from 21 bone marrow transplant (BMT) patients and normal controls were studied for surface expression of HLA-DR, HLA-DQ, and classic T cell markers, including Leu 2, Leu 3, and Leu 4. Although resting T cells from normal subjects did not express HLA-DR or HLA-DQ molecules, up to 86% (range 22-86%) of T cells from BMT recipients expressed HLA-DR. Interestingly, less than or equal to 8% of the cells expressed HLA-DQ, and less than or equal to 3% had receptors for interleukin-2 (IL-2). When T lymphocytes were harvested from BMT recipients one month postransplant, they failed to produce IL-2 constitutively or after stimulation with various mitogens. Further analysis of patient cells revealed that 20-67% of their T lymphocytes were positive for both Leu 2 and Leu 15 (2+, 15+; normal range = 5-8%). Since 2+, 15+ cells from normal subjects have potent suppressor activity, we tested whether the cells from BMT recipients would suppress production of IL-2 from normal cells. In coculture studies, we found that cells from 5/5 BMT patients suppressed normal IL-2 production up to 70%. If patient cells were irradiated (3000 rads) prior to coculture, suppressor activity was abrogated. We propose that the cells described here may play a prominent role in the slow recovery of the immune system in BMT recipients.

Anemia, Aplastic↗
PubMed1987

Extension of survival of rat parathyroid allografts by depletion of Ia donor cells plus preoperative cyclosporine.

Methods that avoid chronic immunosuppression of transplant recipients must be developed to eliminate the various risk factors associated with such treatment (e.g., increased infections and malignancies). Pretransplant treatment of the graft with anti-Ia serum plus complement to eliminate "passenger cells" is one such method. An alternative approach is short-term treatment of the recipients with cyclosporine (CsA). In this study, parathyroid glands from Lewis X Brown Norway rats were cultured for one week at 37 degrees C and treated with anti-Ia and complement. Treated glands were transplanted into parathyroidectomized, hypocalcemic Wistar-Furth recipients that had received 30 mg/kg of CsA once a day for the three days prior to transplant. At 1 year posttransplant, 67% of the recipients had functional parathyroid allografts. Control rats (no CsA; fresh, untreated glands) rejected their grafts within 28 days. Controls given three days of CsA and transplanted with fresh, untreated glands all had functional grafts for greater than 56 days (median survival: 80.5 days). Prolongation of allograft survival with short-term, preoperative CsA demonstrates the efficacy of immunosuppression given only at the time of antigen presentation. This course of CsA allowed for indefinite graft survival when the recipient received a graft previously cultured and treated with Ia antiserum. These results are encouraging and should be evaluated further to determine whether similar approaches will be useful in human transplants.

Animals↗
PubMed1987

Multiple sclerosis and systemic lupus erythematosus. Occurrence in two generations of the same family.

Multiple sclerosis (MS) and systemic lupus erythematosus (SLE) have overlapping clinical features and laboratory findings. It has, in fact, been hypothesized that MS and SLE have a common etiology. Usually MS and SLE are considered to have autoimmune pathogenesis, and both are chronic diseases that can respond to steroids. Some patients are diagnosed with either MS or SLE but subsequently develop the other disease. We described a family where multiple members of one generation have SLE and two members of the preceding generation have MS. Histocompatibility typing did not reveal any association between HLA inheritance of genes and incidence of severity of disease.

Adult↗