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Biomedical subjects

N Flomenberg

Publications and source records attributed to N Flomenberg.

At least 73 records · Page 4Linked to original sources
PubMed1987

M241 (CD1) expression on B lymphocytes.

The human thymus leukemia-like antigens (CD1a-c) consist of three similar glycoproteins found on subpopulations of normal thymocytes, T cell acute leukemias, and cutaneous dendritic cells. The CD1c antigen recognized by the M241 monoclonal antibody was detected on the circulating mononuclear cells of three children with severe combined immunodeficiency disease (SCID). Two-color immunofluorescence analysis demonstrated that M241 expression (43 to 95%) was limited to cells expressing the B cell-restricted antigens B4 (CD19), B1 (CD20), and surface immunoglobulin. To confirm M241 expression on normal cells of the B lineage rather than aberrant expression limited to SCID B cells, its expression was demonstrated serologically and biochemically on purified B cells from spleen, tonsil, and peripheral blood. Parallel analyses with monoclonal antibodies NA1/34 and 4A76 demonstrated that the CD1a and CD1b molecules were negative on all B cells that were studied. It has been hypothesized that the CD1 molecules represent the human counterpart of the murine thymus leukemia antigens due to their similar size, limited tissue distribution, and association with beta 2-microglobulin. This study suggests that a subset of CD1 antigens detected by M241 (CD1c) may represent a human analog of a murine Qa antigen due to its extended distribution on normal peripheral B cells.

Antibodies, Monoclonal↗
PubMed1987

Autocytotoxic and autosuppressor T-cell lines generated from autologous lymphocyte cultures.

Limiting dilution analyses have demonstrated both the generation and suppression of autocytotoxic cells following in vitro stimulation with autologous peripheral blood mononuclear leukocytes (PBL). Therefore, in order to isolate and characterize the autocytotoxic lymphocytes, interleukin 2-dependent cell lines were derived from autologous mixed lymphocyte microcultures. The cell lines were screened for cytolytic activity against autologous phytohemagglutinin-activated lymphoblasts, autologous and allogeneic B-lymphoblastoid cell lines (B-LCL), and the natural killer target K562. Of 189 cell lines analyzed, 26 demonstrated cytotoxicity against autologous target cells. Cell surface phenotyping of all cell lines indicated that they were of T lymphocyte lineage. Two autocytotoxic T-cell clones were subsequently derived in similar fashion. Cell lines were also screened for autoregulatory activity. Two cells lines were identified that inhibited the generation of autocytotoxicity. Neither of the autoregulatory lines was capable of directly lysing an autocytotoxic line, suggesting that these autosuppressor cells exert their inhibitory effect by a mechanism other than direct lysis of the autocytotoxic effector cell. These findings indicate that through the application of limiting dilution analysis and in vitro cell culture techniques, autocytotoxic and autosuppressor lymphocyte populations can be isolated and utilized to analyze the cellular interactions involved in maintaining self-tolerance.

Autolysis↗
PubMed1987

Relevance of autocytotoxic and autoregulatory lymphocytes in the maintenance of self tolerance.

The state of self tolerance may well be an amalgam of many processes including (but not necessarily limited to) clonal deletion and specific suppressor cell networks. Cells with autoaggressive potential are clearly present in the blood of healthy individuals and have been implicated in diseases states. Given the critical importance of maintaining self tolerance, it is not at all surprising that several mechanisms appear to play a role in this process. Attempts to harness and manipulate these various mechanisms in order to prevent allograft rejection or to treat autoimmune diseases should prove to be exciting areas of investigation in the years ahead.

Animals↗
PubMed1987

Graft rejection in recipients of T-cell-depleted HLA-nonidentical marrow transplants for leukemia. Identification of host-derived antidonor allocytotoxic T lymphocytes.

Clinical trials with bone marrow depleted of donor T lymphocytes indicate that both the incidence and severity of graft-versus-host disease (GVHD) in patients undergoing bone marrow transplantation (BMT) for treatment of leukemia are greatly reduced. However, there has been a concurrent increase in the incidence of graft rejection, particularly among recipients of HLA-nonidentical marrow grafts. In order to investigate the nature of graft failure, peripheral blood mononuclear cells (PBMC) present at the time of graft failure have been characterized by phenotypic and functional analyses in 5 recipients of HLA-nonidentical marrow grafts. Rejection of HLA-nonidentical marrow grafts was associated with the emergence of host-derived T lymphocytes in all 5 patients. In 3 of these patients, the cells could be tested directly for cell-mediated cytotoxicity. Antidonor cytotoxicity was detected in each of these 3 patients. In one patient the target specificity of the cytotoxic lymphocytes was identified as the donor class I HLA antigen, HLA-B7. None of the patient PBMC mediated cytotoxicity against the natural killer cell target K562.

Bone Marrow Transplantation↗
PubMed1986

Complexity of the supertypic HLA-DRw53 specificity: two distinct epitopes differentially expressed on one or all of the DR beta-chains depending on the HLA-DR allotype.

The supertypic HLA-DRw53 specificity is associated with three allelic class II specificities defined by alloantisera: HLA-DR4, -DR7, and DRw9. The present study demonstrates the complexity of this supertypic DR specificity by comparing two DRw53-related determinants defined by the monoclonal antibodies PL3 and 109d6. For every HLA-DR4 cell line tested, both monoclonal antibodies were found to bind to the same subpopulation of DR molecules. This PL3+, 109d6+ DR subpopulation is also found on most, but not all, DR7+ cell lines with a beta-chain pattern that is identical to the beta-chain pattern of the PL3+, 109d6+ subpopulation on DR4 cell lines. However, some DR7+ cells which carry the HLA haplotype Bw57, DR7, DRw53, DQw3 were also found which completely lack the expression of the 109d6 determinant, but continue to express the PL3 determinant and some of the DRw53 determinants recognized by alloantisera. This results from the fact that the PL3 determinant is expressed on all of the DR molecules found on DR7 cells, including the distinct subpopulation of molecules that carry the HLA-DR7 determinant recognized by the monoclonal antibody SFR16-DR7. This PL3+, SFR16-DR7+ subpopulation does not carry the 109d6 determinant, demonstrating that the PL3 and 109d6 DRw53-related determinants are distinct and can be expressed on a different number of DR molecules, depending on the allotype of the cells. Blocking studies were also performed by using these monoclonal antibodies with alloreactive HLA-DR7-specific cytotoxic T cell clones. In these studies, the T cell-defined HLA-DR7 determinants were found to be carried by the same subpopulation of DR molecules recognized by the HLA-DR7-specific monoclonal antibody and not carried by the DR molecules recognized by 109d6. The DR7+ cell lines which do not express the 109d6 determinant also fail to express another supertypic determinant recognized by the monoclonal antibody IIIE3 carried on this molecule. Furthermore, no additional allelic forms of this unique DR beta-chain were found associated with the nonpolymorphic DR alpha-chain on these cells, suggesting that this DR beta-chain gene is not expressed. These cells also behave as homozygous typing cells for the Dw11 subtype of DR7 in HLA-D typing in the mixed lymphocyte culture assay. This suggests that the lack of expression of a specific class II gene may contribute additional genetic polymorphism within the known HLA-DR allotypes.

Alleles↗
PubMed1985

Generation and regulation of autocytotoxicity in mixed lymphocyte cultures: evidence for active suppression of autocytotoxic cells.

Using limiting dilution analysis, we have detected both the generation and suppression of autocytotoxic cells following autologous or allogeneic stimulation in vitro. Assay conditions were established in which the cytotoxic response toward an allogeneic sensitizing cell was consistent with a traditional single-hit kinetic model. Under identical conditions, cytolytic activity toward autologous phytohemaglutinin-activated lymphoblasts exhibited a distinct biphasic response. At low responder cell doses, a clear autocytotoxic response was observed. However, at higher responder cell numbers, this autocytotoxic reaction disappeared. This biphasic pattern of autocytotoxicity developed after stimulation with allogeneic or autologous peripheral blood mononuclear leukocytes (PBL) or Epstein-Barr virus-transformed B cells. This pattern of response is consistent with the counterpoised actions of two distinct cell populations, an autoaggressive population and a lower frequency autosuppressor population. Autocytotoxicity was not the result of mitogenic or xenogeneic antigenic stimulation, as it was observed after stimulation with autologous PBL in autologous serum and an autologous interleukin 2 preparation. Thus, cells capable of autocytotoxicity are present in peripheral blood but at a lower frequency than allocytotoxic T lymphocytes. Furthermore, autoaggressive cells are down-regulated by an autologous suppressor population. These findings suggest that immunologic self-tolerance is, at least in part, an actively maintained condition. Disturbances in this autoregulatory network may have relevance to the pathogenesis of some autoimmune diseases and graft-versus-host disease.

B-Lymphocytes↗
PubMed1985

Quantitation of T lymphocytes in human bone marrow by a limiting dilution assay.

A limiting-dilution microculture assay (LDMA) for quantitation of T lymphocytes in human bone marrow is described. Phytohemagglutinin (PHA)-responsive T cells are maintained in interleukin 2 (IL-2)-containing medium with feeder cells in a total volume of 20 microliter. After 16 days of culture, each well is scored by microscopic examination as positive or negative based on the presence or absence of cell growth. A limiting dilution analysis of the relationship between the number of cells seeded per well and the fraction of wells without growth demonstrate that the data are consistent with single-hit kinetics. Minimum chi square statistics were used to establish the line of best fit to calculate the T lymphocyte frequency in a sample. This method for enumeration of T cells was applied to untreated samples of bone marrow, soybean-agglutinin-negative (SBA-) marrow, and soybean-agglutinin-negative marrow cells subjected to a single sheep red blood cell (SRBC) rosette (SBA-E-) or double SRBC rosette (SBA-E-E-) depletion. It was demonstrated that the LDMA can detect as few as 4.3 X 10(5) T cells in a total of 10(9) bone marrow mononuclear cells. The assay system also allows for a comparison of T lymphocytes in the untreated marrow with the T-cell-depleted marrow samples. The mean number of T cells in untreated marrow was 1 X 10(9) and in T-cell-depleted samples 4.3 X 10(5). This corresponds to a 3.5 log or 99.96% reduction in total T cell number by the SBA-E-rosette technique. The phenotypic analysis of single positive wells as well as pooled cells from all positive wells indicate that at least 95% of the wells scored microscopically as positive for T cell growth did in fact contain T cells. The assay requires only 1 X 10(6) mononuclear cells for complete analysis and, therefore, compares favorably with previously published methods.

Bone Marrow Cells↗
PubMed1984

Alteration of T-cell functions by infection with HTLV-I or HTLV-II.

Two functionally different types of human T-cell clones, one with helper function and two with specific activity, were infected with different isolates of HTLV-I and HLTV-II. Both types of human T cells showed alterations in specific function after infection with either of the HTLV subgroups. Before HTLV infection, the T-cell clone with helper function proliferates and provides help to B cells only in the presence of both a specific soluble antigen (keyhole limpet hemocyanin) and histocompatible antigen-presenting cells. After HTLV infection, these cells respond with increased proliferation and indiscriminant stimulation of polyclonal immunoglobulin production by B cells, regardless of the histocompatibility of the antigen-presenting cells or the presence of the soluble antigen. Infection of the normal cytotoxic T-cell clones led to a dimunition or loss of the cytotoxic function. The results of these studies suggest some possible mechanisms for induction of immune deficiency and of polyclonal B-cell activation by viruses of the HTLV family.

Clone Cells↗
PubMed1984

Reactivity patterns with HLA-A2 variants indicate lack of identity between determinants defined by monoclonal antibodies and cytotoxic-T-cell clones.

The anti-HLA-A2 monoclonal antibodies (MoAb) CR11-351 and 4B inhibit the binding of each other to HLA-A2 lymphoid cells and block the cytotoxicity of the anti-HLA-A2 cytotoxic-T-cell clone R32. The blocking does not reflect reactivity of the MoAb CR11-351 and 4B and of the cytotoxic-T-cell clone R32 with the same determinant, since they display differential reactivity with four HLA-A2 variants which carry amino acid substitutions at different positions. These results show for the first time in the human system that Class I HLA variants represent useful reagents to compare the fine specificities of monoclonal antibodies and T-cell clones. Furthermore our data suggest that T-cell recognition depends upon the tertiary structure of the antigen.

Antibodies, Monoclonal↗
PubMed1984

HLA class I specific T lymphocyte clones with dual alloreactive functions.

Four human T lymphocyte clones exhibiting proliferative responses to class I HLA antigens were isolated from an in vitro mixed lymphocyte culture (MLC). Three clones expressed the Leu-2+3- phenotype and demonstrated proliferation in response to HLA-B8, while the fourth clone expressed the Leu-2-3+ phenotype and proliferated in response to HLA-A2. These clones were also cytotoxic towards cells bearing the same target antigens. Blocking studies utilizing monoclonal antibodies demonstrated that proliferation was triggered by determinants on the class I molecule itself, and these determinants appear to be spatially close to those which determine serologic allospecificity. These findings support the concept that the class I molecules themselves are the weak MLC stimulating determinants previously mapped to the HLA-A and B regions of the major histocompatibility complex.

Cells, Cultured↗
PubMed1984

HLA class-II-specific T-lymphocyte clones with dual alloreactive functions.

The relationship between T lymphocytes that proliferate in response to HLA class II antigens and those that mediate the cytotoxic response toward HLA class II target antigens was investigated. Alloreactive T-cell clones were derived under conditions in which the likelihood of clonality was high. Three populations of HLA class-II-specific T cells were identified. Two of these populations exhibited only HLA class-II-directed cytotoxicity or HLA class-II-induced proliferation. The third population of T cells exhibited both of these responses.

Antibody Specificity↗