Chimerism, graft survival, and withdrawal of immunosuppressive drugs in HLA matched and mismatched patients after living donor kidney and hematopoietic cell transplantation.

Thirty-eight HLA matched and mismatched patients given combined living donor kidney and enriched CD34(+) hematopoietic cell transplants were enrolled in tolerance protocols using posttransplant conditioning with total lymphoid irradiation and anti-thymocyte globulin. Persistent chimerism for at least 6 months was associated with successful complete withdrawal of immunosuppressive drugs in 16 of 22 matched patients without rejection episodes or kidney disease recurrence with up to 5 years follow up thereafter. One patient is in the midst of withdrawal and five are on maintenance drugs. Persistent mixed chimerism was achieved in some haplotype matched patients for at least 12 months by increasing the dose of T cells and CD34(+) cells infused as compared to matched recipients in a dose escalation study. Success of drug withdrawal in chimeric mismatched patients remains to be determined. None of the 38 patients had kidney graft loss or graft versus host disease with up to 14 years of observation. In conclusion, complete immunosuppressive drug withdrawal could be achieved thus far with the tolerance induction regimen in HLA matched patients with uniform long-term graft survival in all patients.

Requirement for interactions of natural killer T cells and myeloid-derived suppressor cells for transplantation tolerance.

The goal of the study was to elucidate the cellular and molecular mechanisms by which a clinically applicable immune tolerance regimen of combined bone marrow and heart transplants in mice results in mixed chimerism and graft acceptance. The conditioning regimen of lymphoid irradiation and anti-T cell antibodies changed the balance of cells in the lymphoid tissues to create a tolerogenic microenvironment favoring the increase of natural killer T (NKT) cells, CD4+ CD25+ regulatory T cells and Gr-1+ CD11b+ myeloid-derived suppressor cells (MDSCs), over conventional T cells (Tcons). The depletion of MDSCs abrogated chimerism and tolerance, and add back of these purified cells was restorative. The conditioning regimen activated the MDSCs as judged by the increased expression of arginase-1, IL-4Rα and programmed death ligand 1, and the activated cells gained the capacity to suppress the proliferation of Tcons to alloantigens in the mixed leukocyte reaction. MDSC activation was dependent on the presence of host invariant NKT cells. The conditioning regimen polarized the host invariant NKT cells toward IL-4 secretion, and MDSC activation was dependent on IL-4. In conclusion, there was a requirement for MDSCs for chimerism and tolerance, and their suppressive function was dependent on their interactions with NKT cells and IL-4.

Tolerance and withdrawal of immunosuppressive drugs in patients given kidney and hematopoietic cell transplants.

Sixteen patients conditioned with total lymphoid irradiation (TLI) and antithymocyte globulin (ATG) were given kidney transplants and an injection of CD34+ hematopoietic progenitor cells and T cells from HLA-matched donors in a tolerance induction protocol. Blood cell monitoring included changes in chimerism, balance of T-cell subsets and responses to donor alloantigens. Fifteen patients developed multilineage chimerism without graft-versus-host disease (GVHD), and eight with chimerism for at least 6 months were withdrawn from antirejection medications for 1-3 years (mean, 28 months) without subsequent rejection episodes. Four chimeric patients have just completed or are in the midst of drug withdrawal, and four patients were not withdrawn due to return of underlying disease or rejection episodes. Blood cells from all patients showed early high ratios of CD4+CD25+ regulatory T cells and NKT cells versus conventional naive CD4+ T cells, and those off drugs showed specific unresponsiveness to donor alloantigens. In conclusion, TLI and ATG promoted the development of persistent chimerism and tolerance in a cohort of patients given kidney transplants and hematopoietic donor cell infusions. All 16 patients had excellent graft function at the last observation point with or without maintenance drugs.

Vaccination of patients with B-cell lymphoma using autologous antigen-pulsed dendritic cells.

In this pilot study, we investigated the ability of autologous dendritic cells pulsed ex vivo with tumor-specific idiotype protein to stimulate host antitumor immunity when infused as a vaccine. Four patients with follicular B-cell lymphoma received a series of three or four infusions of antigen-pulsed dendritic cells followed, in each instance, by subcutaneous injections of soluble antigen two weeks later. All patients developed measurable antitumor cellular immune responses. In addition, clinical responses have been measured with one patient experiencing complete tumor regression, a second patient having partial tumor regression, and a third patient resolving all evidence of disease as detected by a sensitive tumor-specific molecular analysis.

Immunoregulatory T cell circuits in man. Alloantigen-primed inducer T cells activate alloantigen-specific suppressor T cells in the absence of the initial antigenic stimulus.

Although alloantigen-specific suppressor T cells are generated in MLR, the cellular signals that lead to activation of suppressor T cells as opposed to cytotoxic T cells are unknown. The current study was undertaken to characterize interactions among T cell subsets involved in the generation of suppressor T cells in MLR. Human peripheral blood Leu-2+ (suppressor/cytotoxic) and Leu-3+ (helper/inducer) T cell subsets were activated with allogeneic non-T cells and then examined for their inductive effects on fresh autologous T cells. Fresh Leu-2+ cells proliferated in response to alloantigen-primed Leu-3+ cells and subsequently suppressed the response of fresh autologous Leu-3+ cells to the original, but not third party, allogeneic stimulator non-T cells. Moreover, only Leu-2+ cells that lacked the 9.3 marker, an antigen present on the majority of T cells including precursors of cytotoxic T cells, differentiated into suppressor cells. The alloantigen-specific suppressive effect of Leu-2+,9.3-cells was not mediated by cytolysis of allogeneic stimulator cells, nor could it be explained by alteration of MLR kinetics. Suppression was observed only when activated Leu-2+ cells were added to fresh MLRs within 24 h of initiation of cultures, suggesting that these cells block an early phase of the activation of Leu-3+ cells in MLR. These results indicate that alloantigen-primed inducer T cells can activate alloantigen-specific suppressor T cells in the absence of allogeneic stimulator cells.

Evidence for the involvement of CD56 molecules in alloantigen-specific recognition by human natural killer cells.

In recent reports we have described the generation of natural killer (NK) lines devoid of CD3/TCR structures but with apparent specificity for allogeneic target cells. Using one such NK line as an immunogen, we now report the generation of two monoclonal antibodies (mAbs), designated 2-13 and 5-38, which bind selectively to the majority of CD3-, CD16+, CD56+ lymphocytes and inhibit the lysis of specific allogeneic target cells by a panel of alloreactive NK lines. By contrast, these mAbs had no effect on classical NK cell mediated lysis of K562 cells or major histocompatibility-restricted T cell-mediated cytolysis. Immunoprecipitation of radiolabeled NK lines followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the target molecules of both mAbs have a molecular mass of approximately 180 kD. Leu 19, a well-described anti-CD56 mAb, precipitated a 180 kD protein from NK cells, and the binding of Leu 19 to NK cells was blocked by pretreatment with both 2-13 and 5-38. However, in contrast to these mAbs, Leu 19 had no effect on the cytolytic activity of allospecific NK cells. Sequential immunoprecipitation analysis revealed that all three mAbs recognized distinct molecular species of CD56. We interpret these findings as indicating that multiple isoforms of CD56 are differentially expressed on NK lines and play critical roles in the recognition/interaction of these cells with their specific allogeneic targets.

Generation of antigen receptor-specific suppressor T cell clones in man.

We have shown previously that CD8+ T cells proliferate upon exposure to autologous, antigen primed CD4+ T cells, and suppress the response of fresh T cells to the priming antigen but not irrelevant antigens. The stimulus and target of suppression in this system appears to be the antigen receptor on the surface of CD4+ cells, rather than the nominal antigen. In the current study, alloantigen primed CD4+ inducer cells and IL-2-containing medium were used to generate clones of suppressor cells from several individuals. The clones inhibited the response of fresh autologous T cells only to the original allogeneic stimulator cell and to stimulator cells that shared HLA-DR antigens with the priming cell. The clones were also genetically restricted, since they inhibited the response of HLA-A,B-compatible but not HLA-A,B-incompatible individuals. The availability of a method for reproducibly generating antigen receptor-specific suppressor T cell clones in vitro should make it possible to clarify the mechanism, whereby such cells are activated and exert their suppressive effect.

Ia antigen on peripheral blood mononuclear leukocytes in man. II. Functional studies of HLA-DR-positive T cells activated in mixed lymphocyte reactions.

Blast transformation of T cells in response to allogeneic lymphocytes is followed by expression of HLA-DR antigen on up to 60% of the T cells. Murine monoclonal antibody to HLA-DR antigen was used to separate alloactivated T cells into those T cells that express high quantities of DR antigen (DR+) and those that express little or no DR antigen (DR-), and each population was tested in a variety of assays. DR+, but not DR-, T cells stimulated fresh allogeneic and autologous T cells to proliferate and supported proliferation by fresh autologous T cells to soluble antigens. Alloactivated T cells were suppressive of fresh mixed lymphocyte reactions (MLR) and suppression by irradiated DR+ T cells was specific for the DR antigens of the initial stimulator cell. Suppression of the MLR by DR+ T cells was not a result of altered kinetics or cell-mediated cytotoxicity. DR+ T cells released soluble factors that suppressed fresh allogeneic responses. These data indicate that alloactivated DR+ T cells may provide antigen-specific feedback inhibition of the MLR.

Suppression of the mixed lymphocyte reaction in man by a soluble T-cell factor. Specificity of the factor for both responder and stimulator.

J.H., an HLA-Dw2 homozygous multiparous woman, fails to respond to her husband, W.H. (HLA Dw1,-) in the unidirectional mixed lymphocyte reaction. T cells from J.H. were previously shown to suppress the responses of Dw2-positive cells but not Dw2-negative cells to W.H. We now report that a soluble factor released into the supernate of the mixed lymphocyte reaction by J.H. T cells, mediates this suppression. Like the cell from which it is derived, the factor is highly specific for HLA Dw2 in the responder cell and partially specific for the stimulatory alloantigen.

Antibodies to membrane structures that distinguish suppressor/cytotoxic and helper T lymphocyte subpopulations block the mixed leukocyte reaction in man.

Two major subsets of human T lymphocytes that are functionally analogous to the mouse Lyt-2+ and Lyt-2- subsets have been defined by their expression of two thymus-dependent membrane antigens, Leu-2 and Leu-3. Leu-2+,3- cells have suppressor/cytotoxic functions and Leu-2-,3+ cells have helper functions. These studies were designed to determine the effects of adding IgG1 monoclonal anti-Leu-2 and anti-Leu-3 antibodies to the mixed leukocyte reaction (MLR). At high concentrations, each antibody partially inhibited the proliferative response of unseparated T cells and abolished the response of the isolated subset having the appropriate phenotype. An IgG1 monoclonal antibody to HLA-A2 and an IgG2a antibody to Leu-1, a pan-T antigen, failed to inhibited the MLR. These results suggest that the Leu-2 and Leu-3 antigens may have a direct role in the mechanism whereby T cells recognize and respond to alloantigen.

Ia antigen on peripheral blood mononuclear leukocytes in man. I. Expression, biosynthesis, and function of HLA-DR antigen non-T cells.

Murine monoclonal antibodies to monomorphic components of HLA-DR antigen were used to analyze the distribution and function of DR molecules on non-T mononuclear leukocytes from peripheral blood. On the basis of indirect immunofluorescence and complement-mediated cytolysis. DR antigen was detected on approximately 70% of non-T cells (DR+) and could not be detected on approximately 30% of non-T cells (DR-). A fluorescence-activated cell sorter was used to separate non-T cells into DR+ and DR- populations, and each population was studied. At least one-third of DR- cells were monocytes, and the remainder were surface-immunoglobulin-negative lymphocytes. Analysis of [35S]methionine-labeled proteins by the method of two-dimensional polyacrylamide gel electrophoresis indicated that DR+, but not DR-, cells biosynthesize DR molecules DR+ cells stimulated strongly in the autologous and allogeneic mixed lymphocyte reactions (MLR) and supported T cell proliferation to soluble antigens, whereas DR- cells stimulated in the allogeneic MLR but failed to stimulate in the autologous MLR or to support T cell proliferation to soluble antigens. When present continuously in culture, one monoclonal anti-DR antibody (antibody 2.06) modestly inhibited T cell proliferative responses. Another antibody (antibody 1.35) markedly enhanced the autologous MLR and the proliferative response to soluble antigens, but had no effect on the allogeneic MLR. These data suggest that DR+ and DR- non-T populations are functionally distinct, and that DR antigen may be required for presentation of soluble antigen and stimulation in the autologous MLR. Antigens in addition to DR may stimulate allogeneic T cell proliferation.

Identification of a human OX-40 ligand, a costimulator of CD4+ T cells with homology to tumor necrosis factor.

The human OX-40 cell surface antigen is a CD4+ T cell activation marker that acts as a costimulatory receptor and is a member of the nerve growth factor receptor/tumor necrosis factor (TNF) receptor family. Using a soluble form of the receptor, the extracellular region fused with human immunoglobulin Fc, we expression cloned the human OX-40 ligand cDNA from a library derived from an activated B lymphoblastoid cell line MSAB. The encoded protein is identified as gp34, a type II transmembrane antigen previously known to be expressed only by human T cell lymphotropic virus 1-infected cells. We describe gp34 as a new member of the TNF family, and find that the recombinant ligand expressed in COS cells costimulates phorbol myristate acetate, phytohemagglutinin, and anti-CD3-induced CD4+ T cell proliferation.

A suppressor T cell of the mixed lymphocyte reaction in man specific for the stimulating alloantigen. Evidence that identity at HLA-D between suppressor and responder is required for suppression.

It has previously been shown that J.H., a human leukocyte antigen (HLA)-Dw2 homozygous multiparous woman, fails to respond in a mixed lymphocyte reaction (MLR) to her Dw1 homozygous husband W.H., and that her T cells suppress the responses of HLA matched responders to W.H. The present studies take advantage of the observation that J.H. suppressor cells resist a dose of gamma-irradiation which functionally eliminates her MLR responder cells. J.H. cells, depleted of alloreactive cells, suppress the responses of Dw2 heterozygous or homozygous cells to W.H., regardless of their associated HLA-A or B antigens. Only when W.H. or a few other cells are present as the irradiated stimulator is J.H. suppression of Dw2 responses detected. Thus, the J.H. suppressor T cell recognizes determinants in the irradiated stimulator cells as well as D locus products in the responder.

Immunoglobulin secretion in the human autologous mixed leukocyte reaction. Definition of a suppressor-amplifier circuit using monoclonal antibodies.

The induction of immunoglobulin (Ig) synthesis in the autologous MLR has an absolute requirement for helper/inducer (Leu-3) T cells, whereas an excess of suppressor/cytotoxic (leu-2) cells suppresses the response. The current study was an effort to assess the immunoregulatory potential to T cells activated in the autologous mixed-leukocyte response (MLR). T cells were cultured with autologous non-T cells for 8-9 d, after which the activated T cells were fractionated into subsets with monoclonal antibodies to T cell markers and HLA-DR antigen. Each population was co-cultured in fresh autologous MLR, and on the 8th day of culture, Ig-secreting cells were measured in a reverse hemolytic plaque assay. The results show that activated Leu-2, DR+ T cells, but neither Leu-2, DR- nor Leu-3 T cells, were at least 50 times more potent as suppressors of IgM and IgG synthesis than fresh Leu-2 cells alone. The activation of this Leu-2, DR+ subpopulation required Leu-3 cells in the primary culture. Furthermore, in the absence of Leu-2 cells in the second culture, little or no suppression was observed, suggesting that the Leu-2, DR+ cells act to amplify or induce suppressor effects of fresh Leu-2 cells. This indicates that at least two distinct subpopulations of Leu-2 cells are required for maximal suppression of an immune response, and that immunoregulatory circuits analogous to those described in the mouse exist in man.

Natural killer lines and clones with apparent antigen specificity.

Fresh CD3-, CD16+ lymphocytes that adhered to selected allogeneic lymphoblastoid cell lines (LCL) were cultured with LCL in the presence of IL-2-containing medium. The resulting lines as well as clones derived from these lines expressed CD16 and/or CD56, but lacked detectable CD3 or TCR-alpha/beta or TCR-gamma/delta complexes on the cell surface. Northern blot analysis failed to detect CD3 epsilon or TCR-beta transcripts, but revealed the presence of a TCR-gamma chain transcript in one of these lines. In addition to displaying potent cytolytic activity against K562 erythroleukemia cells (a classical NK target), the vast majority of these lines and clones lysed their specific stimulator LCL to a significantly greater extent than irrelevant LCL. This selective killing was inhibited by the addition of cold stimulator LCL or K562 cells, or anti-LFA 1 mAbs, but not by irrelevant LCL or mAbs to CD3, class I or class II MHC antigens. These results indicate that some CD3- lymphocytes, phenotypically indistinguishable from NK cells, can recognize and lyse allogeneic targets in a specific manner.

Development of CD8alpha-positive dendritic cells from a common myeloid progenitor.

Dendritic cells (DCs) are critical in both initiating adaptive immune responses and maintaining tolerance to self antigens. These apparently contradictory roles have been suggested to depend on different subsets of DCs that arise from either myeloid or lymphoid hematopoietic origins, respectively. Although DC expression of CD8alpha is attributed to a lymphoid origin, here we show that both CD8alpha+ and CD8alpha- DCs can arise from clonogenic common myeloid progenitors in both thymus and spleen. Thus, expression of CD8alpha is not indicative of a lymphoid origin, and phenotypic and functional differences among DC subsets are likely to reflect maturation status rather than ontogeny.

AIDS retrovirus induced cytopathology: giant cell formation and involvement of CD4 antigen.

The formation of multinucleated giant cells with progression to cell death is a characteristic manifestation of the cytopathology induced by the AIDS retrovirus in infected T lymphoid cells. The mechanism of giant cell formation was studied in the CD4 (T4/Leu 3) positive T cell lines JM (Jurkat) and VB and in variants of these lines that are negative for cell surface CD4 antigen. By means of a two-color fluorescent labeling technique, multinucleated giant cells in infected cultures were shown to form through cell fusion. Antibody to CD4 specifically inhibited fusion, and uninfected CD4 negative cells, in contrast to uninfected CD4 positive cells, did not undergo fusion with infected cells, suggesting a direct role for the CD4 antigen in the process of syncytium formation. These results suggest that, in vivo, cell fusion involving the CD4 molecule may represent a mechanism whereby uninfected cells can be incorporated into AIDS virus infected syncytia. Because the giant cells die soon after they are formed, this process may contribute to the depletion of helper/inducer T cells characteristically observed in AIDS.

Granulocyte-macrophage colony-stimulating factor promotes differentiation and survival of human peripheral blood dendritic cells in vitro.

Interest in human dendritic cells (DC) has been heightened recently by the discovery that this cell type is a primary target of the human immunodeficiency virus, the causative agent of AIDS. DC are bone marrow-derived cells with an extraordinarily potent ability to promote the immunological activity of T lymphocytes. Unfortunately, since DC constitute less than 0.5% of peripheral blood mononuclear cells and die within a few days of their isolation, they are not readily accessible to study. We report here that granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine with well-recognized effects on granulocyte and macrophage maturation, profoundly affects the morphology and viability of DC isolated from peripheral blood. GM-CSF not only promotes DC survival but also induces DC differentiation to mobile, reversibly adherent cells with long-branched projections. DC cultured in GM-CSF survive for up to 6 wk and retain their ability to stimulate the proliferation of T cells in allogeneic and autologous mixed leukocyte reactions.

A suppressor T cell of the mixed lymphocyte reaction specific for the HLA-D region in man.

The mixed lymphocyte reaction (MLR) is the proliferative response of one individual's lymphocytes cultured in the presence of another individual's lymphocytes. In man, the MLR is elicited by cell surface antigens coded for by the HLA-D gene locus. This locus is among a cluster of genes which are located on the sixth chromosome and which include genes coding for the major histocompatibility antigens HLA-A, B, and C as well as HLA-D. If the stimulator cell possesses D locus antigens not present in the responder, the lymphocytes of the latter will undergo blast transformation resulting in DNA synthesis which can be measured. A vigorous response in the MLR to allogeneic cells is the rule among healthy individuals. We describe studies of a 23-yr-old man whose lymphocytes respond normally to mitogens and soluble antigens but fail to respond to allogeneic cells in the MLR. His medical history is unremarkable except that he received thymic irradiation as an infant. HLA typing revealed that he is homozygous for HLA-A2, B12, and Cw5 as well as for the D locus antigen Dw4. When his lymphocytes were added to the responder lymphocytes of other persons homozygous for the same HLA antigens, their responses to allogeneic cells but not mitogens were suppressed by 50-95%. Their responses to a soluble antigen, tetanus toxoid, were suppressed to a lesser degree. These inhibitory effects were mediated by a relatively radioresistant thymus-derived (T) lymphocyte. Further studies of the requirements for MLR suppression revealed that only persons heterozygous or homozygous for the Dw4 antigen were inhibited by the suppressor T cell. This effect was not altered by differences in the HLA-A, B, or C antigens between the suppressor and responder. It is concluded that genes in or near the HLA-D locus code not only for antigens (primarily on bone marrow-derived (B) cells), that elicit the MLR, but also for structures on T cells, or possibly macrophages, which are recognized by MLR suppressor T cells.

Anti-DNA antibody production by CD5+ and CD5- B cells of patients with systemic lupus erythematosus.

Although the presence of anti-DNA antibody is a hallmark of systemic lupus erythematosus (SLE), neither the subsets of B cells that secrete anti-DNA antibody nor the stimuli responsible for the induction of anti-DNA secretion is known. In particular, the role of CD5+ B cells in human SLE, a distinct subpopulation of antibody-secreting cells shown previously to be a source of anti-DNA antibody in murine models of SLE, is unknown. To approach these questions, we developed a sensitive enzyme-linked immunospot (ELIspot) assay to measure spontaneous secretion of antibody to single-stranded (ss) DNA, double-stranded (ds) DNA, tetanus toxoid, and polyclonal immunoglobulin (Ig) by purified CD5+ and CD5- B cells of 15 SLE patients and 15 healthy control subjects. The B cells of only 1 of 15 healthy subjects secreted a significant level of anti-ssDNA antibody, and none secreted anti-dsDNA. By contrast, in the majority of SLE patients both CD5+ and CD5- B cells secreted IgG and/or IgM anti-ssDNA as well as anti-dsDNA antibody. Further analysis of the anti-ssDNA response revealed that the level of IgG and IgM anti-DNA antibody secretion by CD5- B cells correlated closely with the level of polyclonal Ig production by the same subpopulation (r = 0.81 and 0.70, respectively). In contrast, production of anti-DNA by CD5+ B cells occurred independently of polyclonal Ig production by both CD5+ and CD5- B cell subpopulations. These results suggest that in human SLE there exist two anti-DNA antibody-producing B cell subpopulations with distinct induction mechanisms: one (CD5+), which independently secretes anti-DNA, and another (CD5-), which produces anti-DNA as an apparent consequence of polyclonal B cell activation.