Restoration of immunogenicity to passenger cell-depleted kidney allografts by the addition of donor strain dendritic cells.

The immunogenicity of long-surviving, enhanced (AS X AUG)F1 renal allografts retransplanted into secondary AS recipients was restored by the injection of small numbers of donor strain dendritic cells derived from afferent lymph. Whereas 1 X 10(4) to 5 X 10(4) dendritic cells were able to trigger an acute rejection response, neither the passenger volume of donor strain blood nor 5 X 10(6) T or B lymphocytes were able to do so, thereby demonstrating more than a 100-fold difference in immunogenic potency. It is concluded that intrarenal dendritic cells provide the major immunogenic stimulus of a kidney allograft. These results suggest that the antigenic strength of major histocompatibility complex-incompatible tissue correlates with the content of donor strain dendritic cells. They also provide further evidence that antigens of the major histocompatibility complex behave like conventional antigens unless they are on the surface of allogeneic dendritic cells.

Immunogenicity of retransplanted rat kidney allografts. Effect of inducing chimerism in the first recipient and quantitative studies on immunosuppression of the second recipient.

It has been previously shown that long surviving, enhanced (AS X AUG)F1 rat kidneys residing in a primary AS recipient are not acutely rejected if transferred into a second AS recipient. The reduced immunogenicity of the retransplanted graft was attributed to a depletion of incompatible passenger cells. It is shown here that if the primary AS recipient is made chimeric by x irradiation and injection of (AS X AUG)F1 bone marrow cells, transfer of the long surviving, enhanced graft into a second AS recipient provokes acute graft rejection comparable to that observed when normal (AS X AUG)F1 kidneys are transplanted into untreated AS recipients. Transplantation of passenger cell-depleted AUG kidneys into AS recipients leads to graft rejection, with a median survival time of 22 d. Treatment of these recipients with as little as 1.5 mg/kg cyclophosphamide for 14 d induces prolonged graft survival. By contrast, five times as much cyclophosphamide treatment is required to induce prolonged survival of normal AUG kidneys (i.e., containing incompatible passenger cells) transplanted to AS recipients. These results confirm that the major alloimmunogenic stimulus of rat kidney grafts is provided by the incompatible passenger cells.

Failure of long surviving, passively enhanced kidney allografts to provoke T-dependent alloimmunity. II. Retransplantation of (AS X AUG)F1 kidneys from AS primary recipients into (AS X WF)F1 secondary hosts.

Long surviving, passively enhanced (AS X AUG)F1 kidneys carried by AS recipients were retransplanted into (AS X WF)F1 second hosts. Acute graft rejection did not occur. Only one of six secondary recipients mounted a significant T-dependent IgG lymphocytotoxic antibody response. In all six, generation of cytotoxic T cells was markedly slower and depressed. These results are compatible with the hypothesis that kidney parenchyma, although carrying major histocompatibility complex specificity is able to induce T-independent but not T-dependent alloimmunity. A corollary is that passenger cells are responsible for exciting the T-dependent allimmune response normally observed after grafing. The practical difficulty of eliminating all T-dependent immunogenicity from (AS X AUG)F1 kidneys was emphasized by the observation that a 3-d residence in an intermediate AS recipient was insufficient time to prevent acute graft rejection after retransplantation.

Failure of long surviving, passively enhanced kidney allografts to provoke T-dependent alloimmunity. I. Retransplantation of (AS X AUG)F1 kidneys into secondary AS recipients.

Long survival of (AS X AUG)F1 rat kidney allografts in AS recipients was induced by passive enhancement with AS anti-AUG antiserum at the time of grafting. After 1-3 mo, the kidney allografts were transferred to second AS recipients, either naive or sensitized against AUG tissue. Naive second recipients did not reject the grafts acutely and failed to mount T-dependent immunity against AUG targets. When later challenged with spleen cells carrying the AUG haplotype, the naive second AS recipients showed strong IgM, IgG, and cytotoxic T-cell responses after grafting, and the kidneys were rapidly destroyed by immune rejection in all but one rat. It is concluded that long-surviving kidney allografts fail to activate helper T cells and induce in naive second recipients the same state of unresponsiveness observed in the first recipient.

Human T cells cannot act as autonomous antigen-presenting cells, but induce tolerance in antigen-specific and alloreactive responder cells.

The ability of two HLA-DR-expressing human T cell clones to function as antigen-presenting cells (APC) was investigated using highly purified T cells. The results demonstrated that these T cell clones are unable to act as autonomous APC, and that recognition of nominal or alloantigens on the surface of T cells leads to a state of nonresponsiveness. The first observation was that a T cell clone with specificity for the 306-324 peptide of influenza hemagglutinin (HA), and raised from a DR1 responder, exhibited apparent degeneracy of major histocompatibility complex restriction when cultured with peptide in the presence of peripheral blood mononuclear cells (PBMC) expressing a wide variety of structurally unrelated DR types. However, when the PBMC were pulsed with peptide and washed before coculture with the clone, peptide was exclusively recognized with DR1Dw1. This implied that in the presence of soluble peptide the T cells were displaying ligand to each other, and that the third-party APC were providing costimulatory signals. To test the ability of T cells to act as autonomous APC, accessory cell-free preparations of two DR1-restricted clones were cultured with peptide in the presence or the absence of added B cell APC. T cell purity was established by the absence of proliferation in response to the mitogen phytohemagglutinin (PHA). PHA-nonresponsive T cells were completely unable to proliferate in response to peptide alone; furthermore, preculture of the HA-specific clone, in the complete absence of accessory cells, with the same concentration of peptide (1 microgram/ml) that induced optimal proliferation when presented by conventional APC, led to profound nonresponsiveness. The same phenomenon was also observed when two of three anti-DR1 alloreactive T cell clones were precultured with a DR1-expressing T cell clone. The ability of the DR1-expressing clone to induce nonresponsiveness in anti-DR1 clones correlated with recognition of the DR1 alloantigen on the DR1-expressing clone.

Immune response-associated production of neopterin. Release from macrophages primarily under control of interferon-gamma.

Neopterin, a compound derived from GTP, represents a precursor molecule of biopterin that is an essential cofactor in neurotransmitter synthesis. We have recently reported that in vivo as well as in vitro immune responses are accompanied by an increased release of neopterin and that this phenomenon can be used for the biochemical monitoring of diseases accompanied by hyperimmune stimulation. This article deals with the cellular origin and the control of this immune response-associated neopterin release in vitro. Using highly purified or monoclonal cellular reagents we demonstrate that macrophages (M phi) stimulated with supernatants from activated T cells release large amounts of neopterin into culture supernatants. Further experiments involving induction of neopterin release from M phi with various human recombinant interferons (IFNs) or neutralization of the effect of T cell supernatants with various monoclonal anti-IFN antibodies revealed immune IFN as the active principle. It thus appears that a metabolic pathway so far exclusively known in context with the generation of an essential cofactor of neurotransmitter-synthesis during immune responses is also activated in M phi under stringent control by immune IFN-like lymphokines.

Bone marrow transplantation for chronic myeloid leukemia: the use of histocompatible unrelated volunteer donors.

We treated 17 patients with chronic myeloid leukemia (CML) by bone marrow transplantation using marrow from human leukocyte antigen (HLA)-matched unrelated donors. Patients were conditioned with a combination of in vivo monoclonal antibodies, chemotherapy with daunorubicin (n = 7) or busulfan (n = 10) and cyclophosphamide, and both total body and total lymphoid irradiation. Donor marrow was depleted of T cells by incubation with monoclonal antibodies of the Campath series. Fourteen (88%) of 16 evaluable patients had sustained engraftment. Four (27%) of the 15 evaluable patients developed acute graft-versus-host disease (GVHD) of grade II or greater, and 4 of 12 evaluable patients developed chronic GVHD. Three patients developed hematological and two developed cytogenetic evidence of relapse. Eight patients (47%) survive at a median follow-up of 32 months (range 10-51 months), giving an actuarial survival of 44%. Five patients remain alive without evidence of hematological or cytogenetic relapse, giving an actuarial disease-free survival of 27%. Pneumonitis caused or contributed to death in six of the nine patients who died. We conclude that T-cell depletion can prevent the severest forms of GVHD but also increases the risk of relapse after transplant with unrelated donors, as it does with HLA-identical siblings. Nevertheless the use of matched unrelated donors should be considered for CML patients who lack HLA-identical siblings.

Antibodies against monocytes and endothelial cells in the sera of patients with atherosclerotic peripheral arterial disease.

We looked for antibodies against endothelial cells, monocytes, fibroblasts, lymphocytes and Epstein-Barr virus transformed lymphocytes in the sera of 28 elderly and 18 middle-aged patients with atherosclerotic peripheral arterial disease and 13 controls. Inclusion criteria were symptomatic peripheral arterial disease with intermittent claudication and ankle/radial Doppler pressure ratio less than 0.7 in the patient group and greater than 1 in the controls. The sera were tested using a standard cytotoxic technique against a cell panel of monocytes, T and B lymphocytes from 5 donors, and against endothelial cells, fibroblasts and Epstein-Barr virus transformed lymphocytes from one umbilical cord vein and blood. The sera of 30 of 46 (65.2%) patients showed toxicity against monocytes from at least one member of the cell panel and 12 of 19 sera tested (63%) reacted with endothelial cells. Only one of the control sera was positive against monocytes and none reacted with endothelial cells. None of the sera of either patients or controls contained cytotoxic antibodies against T and B lymphocytes, Epstein-Barr virus transformed lymphocytes or fibroblasts. The selective cytotoxicity suggests that the antibodies detected are not against HLA-antigens (which are expressed by normal lymphocytes and Epstein-Barr virus lymphocytes). Our results suggest that immune phenomena occur in atherosclerosis.

Co-expression of human T cell receptor chains with mouse CD3 on the cell surface of a mouse T cell hybridoma.

In this study we demonstrate that human T cell receptor (TcR) chains can be co-expressed with murine CD3 on the cell surface of a murine T cell hybridoma. Human TcR alpha and beta genes from the Jurkat leukaemic cell line were transfected into a TcR-negative mouse T cell hybridoma, TG40. The Jurkat TcR was successfully co-expressed at the cell surface with mouse CD3 components. Brightly staining transfectants were selected by fluorescence-activated cell sorting, and levels of expression comparable to a normal T cell line were achieved suggesting that the human TcR dimer assembled efficiently with the mouse CD3 complex. Northern blot analysis demonstrated similar levels of TcR messenger RNA to those found in the parental Jurkat line. Although we have not formally demonstrated surface expression of the Jurkat TcR alpha chain, the residual alpha gene transcript which is present in murine TG40 line is non-expressible. In order to test the signalling capacity of this human/mouse complex, the transfectants were stimulated with an anti-V beta 8 monoclonal antibody. This stimulus led to interleukin-2 production by the transfectants, demonstrating the delivery of a transmembrane signal. In addition, B10.A mice were immunised with the transfectants, and the antisera from these mice stained the transfectant and the Jurkat cell line, but not the parental T cell hybridoma. This interspecies transfection approach should now permit us to explore the requirements for T cell activation, the constraints on TcR alpha beta chain pairing, and creates ideal reagents for inducing a mouse anti-human TcR-specific response with a view to producing panels of anti-human TcR monoclonal antibodies.

Prevention of blood transfusion-induced immunization against transplantation antigens by treatment of the blood with antibody.

The experiments reported show that alloantisera directed against the transplantation antigens of allogeneic blood will completely suppress (1) the lymphocytotoxic antibody response to the blood and (2) its ability to sensitize against renal allografts. AS (Ag-B1) rats injected i.v. with 1 ml of August (Ag-B5) blood gave a strong primary (mainly IgM) and secondary (IgG) lymphocytotoxin response. If the August blood was mixed with AS anti-August serum in vitro before injection, the lymphocytotoxin response was completely suppressed. However, rats given the blood-antiserum mixture gave a primary IgM response upon rechallenge with blood. Rats previously primed with blood had substantial but only partial suppression of the secondary response if the secondary stimulus was given as a blood-antiserum mixture. An AS anti-Wistar (Ag-B2) serum, which showed only weak serological cross-reaction with August lymphocytes, could suppress the lymphocytotoxin response to August blood. A protocol of widely spaced injections of August blood was found to sensitize AS rats to (AS X August)F1 renal allografts. If the blood injections were given as a blood-antiserum mixture, sensitization was prevented. In addition, the blood-antiserum mixtures were found to induce a slight degree of immunosuppression. The clinical application of this approach to preventing blood transfusion-induced sensitization is discussed.

The role of the spleen in the rejection and enhancement of renal allografts in the rat.

As rats were splenectomised up to 7 weeks before or at the time of receiving an (AS times August)F1 kidney allograft. Only 2 of 19 splenectomised recipients rejected their grafts within 12 days, and 14 of the 19 survived for more than 100 days. All 19 splenectomised recipients had a marked and often complete suppression of the lymphocytotoxic antibody response to the graft. In contrast, splenecotomy had no effect in suppressing the rejection of (AS times August)F1 renal allografts transplanted to AS recipients previously immunised with August lymphoid tissue, or in AS recipients of homozygous August renal allografts. Splenectomised recipients could be reconstituted with spleen cells from sensitised but not from normal AS rats. Splenectomy was found neither to augment nor diminish the effectiveness of passive enhancement of (AS times August)F1 or August kidneys in AS recipients. Splenectomy of AS recipients 2 or 4 days after an (AS times August)F1 renal allograft was as effective as pregraft splenectomy in suppressing rejection, but there was a deficiency of long survivors in a group splenectomised 1 day after grafting. A working hypothesis to explain these results is presented, and their clinical relevance is discussed.

Mechanisms underlying continued survival of rat kidney allografts after a short period of chemical immunosuppression.

Experiments have been carried out to investigate whether the continued survival of rat kidney allografts induced by two different methods-namely, immunological enhancement or a limited course of drug treatment with cyclosporine or cyclophosphamide, is maintained by similar mechanisms. (AS X AUG)F1 or AUG strain kidneys were transplanted to AS recipients that were treated for 14 days with cyclosporine or cyclophosphamide. The limited course of drug treatments induced indefinitely prolonged, or very extended, allograft survival. Long-surviving F1 kidney grafts were retransplanted into naive AS recipients, and by functioning for more than 100 days proved, like enhanced grafts, to be less immunogenic than normal (AS X AUG)F1 kidneys. Very prolonged survival of homozygous, incompatible AUG kidneys was only observed after the cyclosporine drug regimen-and when these grafts were retransplanted to naive second AS recipients, acute or chronic rejection ensued. However, the rejection was prevented if spleen cells from the first AS recipient were adoptively transferred to the second AS recipient at the time of retransplantation. It was concluded that suppressor cells must be present in the transferred spleen cell populations. The experiments show that, as in the case of immunological enhancement, very prolonged allograft survival brought about by a short course of immunosuppressive drug treatment is accompanied by reduction in graft immunogenicity, and by the induction of suppressor cells.

Immunological enhancement of rat renal allografts using rabbit antisera with specificity for rat transplantation antigens.

Rabbits immunized with particulate and soluble preparations of rat lymphoid tissue of the HO strain produced antisera which reacted without strain specificity on rat lymphocytes. Absorption of the sera with tissue from the AS strain of rat removed the antibodies reacting with AS tissue leaving activity against HO cells only. Studies with backcross rats showed that the antigens detected by these sera were products of the AgB genes or genes segragating with them. The immunosuppressive activity of rabbit antisera specific for Ag-B5 rat transplantation antigens was tested in a rat renal allograft assay. Some of the antisera markedly prolonged the survival of (AS X HO)F1 kidneys transplanted to AS rats. The prolongation of graft survival was not due to ALS activity since the sera were active in the absence of antibody directed against recipient antigens. There was no correlation between in vivo enhancement and anti-donor lymphocytotoxic titres of the xenoantisera.

Prolonged survival of rat leg allografts due to immunological enhancement.

Attempts were made to induce a prolonged survival of leg allografts in rats by means of immunological enhancement. AS rats injected with AS anti-August antiserum accepted (AS X August)F1 kidney allografts for longer than 50 days, but rejected F1 leg allografts within 12-16 days. However, AS rats bearing established, enhanced (AS X August)F1 kidneys accepted F1 leg allografts for periods of 21-207 days. The possibility is discussed that composite tissue allografts can manifest prolonged survival provided that their recipients have passed through the "induction phase" of enhancement and reached the "steady-state" or maintenance phase.

Suppressor cells and their role in the survival of immunologically enhanced rat kidney allografts.

A search has been made for suppressor cells in the spleens of AS rats bearing long-surviving, enhanced AUG strain kidney allografts. The assay consisted of an adoptive transfer of splenocytes from AS rats with enhanced AUG kidneys to normal AS rats that also received test grafts of AUG kidneys. The critical feature of the AUG kidney test grafts was that the native population of passenger cells had been replaced by AS passenger cells--thus reducing, but not eliminating, immunogenicity of the graft. With this assay, it was shown that 2.7-3.5 X 10(8) spleen cells transferred substantial and statistically significant suppression of graft rejection. Suppression was also transferred by spleen cells that did not adhere to nylon wool. It is concluded that suppressor cells are one of the mechanisms ensuring continued survival of enhanced kidney allografts.

Analysis of the alloreactive T cell repertoire in man. I. Differences in precursor frequency for cytotoxic T cell responses against allogeneic MHC molecules in unrelated individuals.

We demonstrate here that in man the frequency of cytotoxic T cells specific for a given set of allo-major histocompatibility complex (MHC) antigens varies among unrelated individuals. This has been established by limiting dilution analysis of human peripheral blood lymphocytes (HPBL) in the presence of irradiated autologous filler cells, T cell growth factors, and irradiated HPBL carrying allo-MHC antigens. Two unrelated individuals were tested against the same panel of allo-MHC antigens. We have been able to identify frequencies of T cells ranging from 1:5,000 to 1:20,000(high), 1:20,000 to 1:60,000(intermediate) and 1:60,000 to 1:100,000(low). In some cases, the precursor frequency of cytotoxic T cells was so low that it was considered to represent nonresponsiveness. The clear differences in precursor frequency suggest that this system is suitable for further analysis of the allo-MHC-specific repertoire in man.

Mediation of acute but not chronic rejection of MHC-incompatible rat kidney grafts by alloreactive CD4 T cells activated by the direct pathway of sensitization.

It has been previously postulated that there are two pathways of sensitization of MHC-incompatible kidney allografts: a direct pathway in which the host responder T cells are activated by MHC-incompatible passenger dendritic cells of the graft, and an indirect pathway, in which graft alloantigens are processed like "nominal" T cell antigens by host accessory cells, and presented as self-MHC restricted moieties. We show here that a rat AS anti-August alloreactive CD4+ T cell line, and a presumptive clone, activated through the direct pathway are capable in an adoptive transfer model of initiating rejection of normal August kidney grafts. However, neither the T cell line nor the presumptive clone initiates rejection of passenger cell-depleted August kidneys. The results support the hypothesis that direct pathway--sensitized T cells play a dominant role in early acute rejection, but not in chronic rejection.

The kinetics of MHC class I and class II expression in rat renal allografts.

We have used in vivo localization of radiolabeled antibodies in a rat renal transplant model to compare the level of induction of major histocompatibility complex (MHC) class I and class II molecules in grafts undergoing rejection with grafts in which rejection was modified by cyclosporine (CsA). MHC class II expression increased in rejecting grafts, peaking on day 4, whereas a later rise in CsA-treated grafts was noted. The use of donor-specific antibodies demonstrated that this was due, in part, to a rise in class II of donor origin. No major differences in MHC class I levels were noted between the two groups until after day 4, when very little antibody localization was seen in the rejecting group. Our results suggest that therapeutic doses of CsA may not prevent the upregulation of class II that occurs during rejection, and that levels of class II are not of prognostic value in kidney transplantation.

Comparison of helper and cytotoxic antirecipient T cell frequencies in unrelated bone marrow transplantation.

Donor/recipient histocompatibility antigen differences initiate acute graft-versus-host disease (GVHD) after bone marrow transplantation. Frequency analysis, using limiting dilution techniques, of functionally defined (helper or cytotoxic) antirecipient T lymphocyte precursors in the peripheral blood of the donor has been shown to be an accurate predictor for the development of moderate-to-severe acute GVHD. Here, we describe a sensitive assay for measuring alloreactive helper (IL-2-producing) T lymphocyte precursor (HTLp) frequencies, and compare the ability of this assay and the cytotoxic T lymphocyte precursor (CTLp) assay to detect HLA- class II and class I differences and to predict clinical outcome in a cohort of unrelated donor/recipient BMT pairs. Twenty-two pairs underwent unrelated donor BMT. Patients with high (> 1:100 x 10(3)) HTLp or CTLp frequencies had a higher incidence of moderate-to-severe (grades II-IV) acute GVHD (80% and 100%, respectively) than pairs with low (< 1:100 x 10(3)) frequencies (40% and 57%, respectively). Ten (45%) patients have died, but all patients with both a low HTLp and low CTLp frequency remain alive. The HTLp and CTLp assays provided similar predictive information for outcome. Given that the HTLp assay is more rapid and less labor intensive, it offers an additional or alternative functional method for donor selection in unrelated donor BMT.

Cytotoxic T lymphocyte precursor frequency analyses in bone marrow transplantation with volunteer unrelated donors. Value in donor selection.

Between May 1989 and February 1994, we performed 48 volunteer unrelated donor BMTs for first chronic phase chronic myeloid leukemia using in vivo T cell depletion for acute graft-versus-host disease (aGvHD) prophylaxis. In 40 cases, adequate material was available to measure the frequency of antirecipient MHC cytotoxic T lymphocyte precursor (CTLp) cells in the blood of potential donors. This supplemented standard serological typing, one-dimensional isoelectric focusing for class I proteins, and allogenotyping for DR and DQ alleles using DNA RFLP analysis in the donor selection process. All recipients were conditioned with cyclophosphamide 120 mg/kg, TBI 1320 cGy, and intravenous Campath 1G. GvHD prophylaxis consisted of CsA, short-course methotrexate, and intravenous Campath 1G. Minimum follow-up in all surviving recipients was 100 days. The development of aGvHD and the probability of leukemia-free survival were compared between the high frequency group (CTLp > 1 in 100,000) (n = 15) and the low frequency group (CTLp < 1 in 100,000) (n = 25). There was a trend for increasing grade of aGvHD, which was statistically significant in the high frequency group when compared with the low frequency group (P = 0.003). Both a high frequency of CTLp (relative risk [RR] = 9.0, P = 0.016) and HLA mismatch (RR = 6.7, P = 0.023) were predictors of severe aGvHD (grade III or IV). Multivariate analysis showed that CTLp group (RR = 3.4, P = 0.015) and CMV status (RR = 3.9, P = 0.008) were predictors of leukemia-free survival. Further investigation showed an interaction between the two, such that CMV seropositive recipients in the high frequency group had a relative risk of 9.4 (P = 0.0001) of treatment failure (death or relapse) when compared with other combinations. We conclude that with our present GvHD prophylaxis regimen, CTLp frequency analysis predicts post-BMT outcome and is a valuable aid in donor selection.