In vitro characterization of rat bone marrow-derived dendritic cells and their precursors

Although the rat is commonly used for basic immunology and transplantation research, phenotypic and functional characterization of rat dendritic cells (DCs) lags behind similar studies in the human and mouse. Therefore, these features were examined using DCs propagated from cultures of rat bone marrow maintained in a medium supplemented with granulocyte-monocyte colony-stimulating factor. Analysis of cytospin preparations of cultured cells showd that DCs arise from OX7+ myelomonocytic precursors. Typical mature rat DCs were morphologically similar to their mouse and human counterparts and expressed major histocompatibility complex (MHC) class II (common part determinant of Ia), OX62 (integrin molecule), OX7 (CD90), ICAM-1 (CD54), and CTLA4 counterreceptor, but were negative for OX8 (CD8), OX19 (CD5), W3/25 (CD4), and ED2, a rat macrophage marker. Functional analysis of OX62+ sorted DCs showed that they could effectively present the soluble antigen ovalbumin to naive T cells in vitro. A combination of anti-MHC class II monoclonal antibody and CTLA4-immunoglobulin inhibited allostimulatory ability more effectively than either reagent alone. Implications for studying the role of DCs in immune responses in the rat are discussed.

[Familial Binswanger-type encephalopathy with Sneddon syndrome]

We reported a family with early onset cerebrovascular disease. Patient 1 (a 36-year-old man) demonstrated a combination of livedo reticularis and cerebral infarction as previously described as Sneddon syndrome. He also showed transient focal neurologic symptoms and mild dementia. Patient 2 (an elder sister of Patient 1) was suffering from migraine. Their father and paternal uncle died of cerebral infarction, which had developed in their thirties or forties. Patients 1 and 2 showed MRI findings compatible with encephalopathy with Binswanger-type. Contrary to the previous reports on Binswanger-type encephalopathy, both of these patients demonstrated decreased levels of fibrinogen as well as those of factor V, together with negative antiphospholipid antibody. Thus, juvenile onset, autosomal dominant inheritance, the diversity of clinical findings and the coagulopathy in this family were characteristic features. The level of thrombin-antithrombin III complex (TAT) was markedly increased in Patient 1. Treatment with antithrombin (argatroban 20mg i.v. everyday for 28 days) not only reduced the level of TAT but also improved the livedo reticularis and neurological findings. Although gene analysis has not been performed yet on this family, this condition is similar to cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL), which involve juvenile cerebral infarction and dementia as well as migraine.

Allogeneic hematolymphoid microchimerism and prevention of autoimmune disease in the rat. A relationship between allo- and autoimmunity

Conventional allogeneic bone marrow transplantation after myeloablation can prevent experimental autoimmunity and has been proposed as treatment for humans. However, trace populations of donor hematolymphoid cells persisting in solid organ allograft recipients have been associated in some circumstances with therapeutic effects similar to replacement of the entire bone marrow. We therefore examined whether inducing hematolymphoid microchimerism without myeloablation could confer the ability to resist mercuric chloride (HgCl2)-induced autoimmunity. Brown-Norway (BN) rats were pretreated with a syngeneic or allogeneic bone marrow infusion under transient FK506 immunosuppression before receiving HgCl2. They were compared with BN rats receiving either no pretreatment (naive) or FK506 alone. Administration of HgCl2 to naive BN rats induced marked autoantibody production, systemic vasculitis and lymphocytic infiltration of the kidneys, liver and skin in all of the animals and a 47% mortality. In contrast, BN rats pretreated with HgCl2-resistant allogeneic Lewis bone marrow and transient FK506 showed less clinical disease and were completely protected from mortality. More specifically, IgG anti-laminin autoantibody production was decreased by 40% (P < 0.05), and there was less histopathological tissue injury (P < 0.005), less in vitro autoreactivity (P < 0.05), less of an increase in class II MHC expression on B cells (P < 0.01), and 22% less weight loss (P < 0.01), compared with controls. Protection from the experimental autoimmunity was associated with signs of low grade activation of the BN immune system, which included: increased numbers of circulating B and activated T cells before administration of HgCl2, and less autoreactivity and spontaneous proliferation in vitro after HgCl2.

Microchimerism, dendritic cell progenitors and transplantation tolerance

The recent discovery of multilineage donor leukocyte microchimerism in allograft recipients up to three decades after organ transplantation implies the migration and survival of donor stem cells within the host. It has been postulated that in chimeric graft recipients, reciprocal modulation of immune responsiveness between donor and recipient leukocytes may lead, eventually, to the induction of mutual immunologic nonreactivity (tolerance). A prominent donor leukocyte, both in human organ transplant recipients and in animals, has invariably been the bone marrow-derived dendritic cell (DC). These cells have been classically perceived as the most potent antigen-presenting cells but evidence also exists for their tolerogenicity. The liver, despite its comparatively heavy leukocyte content, is the whole organ that is most capable of inducing tolerance. We have observed that DC progenitors propagated from normal mouse liver in response to GM-CSF express only low levels of major histocompatibility complex (MHC) class II antigen and little or no cell surface B7 family T cell costimulatory molecules. They fail to activate resting naive allogeneic T cells. When injected into normal allogeneic recipients, these DC progenitors migrate to T-dependent areas of host lymphoid tissue, where some at least upregulate cell surface MHC class II. These donor-derived cells persist indefinitely, recapitulating the behavior pattern of donor leukocytes after the successful transplantation of all whole organs, but most dramatically after the orthotopic (replacement) engraftment of the liver. A key finding is that in mice, progeny of these donor-derived DC progenitors can be propagated ex vivo from the bone marrow and other lymphoid tissues of nonimmunosuppressed spontaneously tolerant liver allograft recipients. In humans, donor DC can also be grown from the blood of organ allograft recipients whose organ-source chimerism is augmented with donor bone marrow infusion. DC progenitors cannot, however, be propagated from the lymphoid tissue of nonimmunosuppressed cardiac-allografted mice that reject their grafts. These findings are congruent with the possibility that bidirectional leukocyte migration and donor cell chimerism play key roles in acquired transplantation tolerance. Although the cell interactions are undoubtedly complex, a discrete role can be identified for DC under well-defined experimental conditions. Bone marrow-derived DC progenitors (MHC class II+, B7-1dim, B7-2-) induce alloantigen-specific hyporesponsiveness (anergy) in naive T cells in vitro. Moreover, costimulatory molecule-deficient DC progenitors administered systemically prolong the survival of mouse heart or pancreatic islet allografts. How the regulation of donor DC phenotype and function relates to the balance between the immunogenicity and tolerogenicity of organ allografts remains to be determined.

The changing immunology of organ transplantation

The engrafted organ becomes a chimera as the recipient's leukocytes station themselves in the transplant. Remarkably, the recipient becomes chimeric as well, in a reverse migration involving immune cells from the graft. Interactions between donor and recipient cells are tolerogenic--a process with implications for the goal of graft acceptance with minimal immunosuppression.

Variable chimerism, graft-versus-host disease, and tolerance after different kinds of cell and whole organ transplantation from Lewis to brown Norway rats

The bidirectional paradigm of tolerance involving reciprocal host vs. graft and graft vs. host reactions was examined after Lewis (LEW)-->Brown Norway (BN) transplantation of different whole organs (liver, intestine, heart, and kidney) or of 2.5 x 10(8) LEW leukocytes obtained from bone marrow, spleen, lymph nodes, and thymus. The experiments were performed without immunosuppression or under 14 daily doses of postoperative tacrolimus, which were continued in weekly doses to 100 days in a "continuous treatment" subgroup, and to 27 days in a short treatment group. Without immunosuppression, all organs and cell suspensions failed to engraft or were acutely rejected. GVHD (usually fatal) was always caused when either the long or short treatment was used for recipients of intestinal grafts and cell suspensions of spleen and lymph nodes. In contrast, both immunosuppressive protocols allowed engraftment of bone marrow cells, liver, heart, and kidney without clinical GVHD, whereas thymus cell suspensions and small doses of whole blood neither engrafted nor caused GVHD. At 100 days, now drug-free for 73 days, the liver, bone marrow, and heart recipients were tolerant in that they accepted all challenge LEW heart and/or liver grafts for 100 more days despite in vitro evidence of donor-specific reactivity (split tolerance). At 200 days, histopathologic studies of the challenge livers were normal no matter what the priming graft. However, the still-beating challenge hearts had a spectrum from normal to severe chronic rejection that defined the tolerogenicity of the original primary grafts: liver best-->bone marrow next-->heart least. Both the GVHD propensity and tolerogenicity in these experiments were closely associated with recipient tissue chimerism 30 and 100 days after the experiments began. The tissue chimerism was invariably multilineage, but the GVHD outcome was associated with T cell over-representation. These observations provide guidelines that should be considered in devising leukocyte augmentation protocols for human whole organ recipients. The results are discussed in relation to the historical tolerance studies of Billingham, Brent, and Medawar; Good; Monaco; and Calne.

Hamster to rat kidney xenotransplantation. Effects of FK 506, cyclophosphamide, organ perfusion, and complement inhibition

Hamster to rat renal xenotransplantation was performed with recipient nephrectomies. Recipients were treated beginning on day 0 with continuous FK 506 monotherapy, a 7-day or open-ended monotherapeutic course of cyclophosphamide (CP), and the two drug regimens combined. CP alone (10 mg/kg/day) prevented a xenospecific antibody response and tripled median survival of the kidney (defined as recipient death) from 6 (control) to 18.5 days whereas FK 506 alone had no effect. The drugs in combination were no better than CP alone (15 days) unless the 5-day course of CP was given at a higher dose (15 mg/kg) and started 3 days preoperatively (79 days). In further experiments, adjuvant measures were added to the minimally effective FK 506/7-day CP regimen which gave a median survival of only 15 days. In the most successful modification, intraoperative antibody depletion by the temporary transplantation of third party hamster liver or en bloc kidneys increased median survival from 15 to 34 and 48 days, respectively. An intraoperative i.v. dose administration of the anticomplement drug K76 instead of antibody depletion increased survival to 26 days. Although the events of kidney rejection were similar to those of heart xenografts and partially forestalled by the antibody inhibiting CP treatment, or by antibody depletion, survival for > 100 days was accomplished in only 5 of 86 treated animals. The poorer survival previously reported with cardiac xenotransplantation is largely explained by the life support requirement of the kidneys. Renal failure was responsible for almost all deaths before 60 days, and subnormal renal failure was a pervasive adverse factor thereafter, frequently caused by pyelonephritis which is suspected to have had an immunologic etiology.

A new protocol for the propagation of dendritic cells from rat bone marrow using recombinant GM-CSF, and their quantification using the mAb OX-62

Bone marrow (BM)-derived dendritic cells (DC) are the most potent known antigen (Ag) presenting cell in vivo and in vitro. Detailed analysis of their properties and mechanisms of action requires an ability to produce large numbers of DC. Although DC have been isolated from several rat tissues, including BM, the yield is uniformly low. We describe a simple method for the propagation of large numbers of DC from rat BM and document cell yield with the rat DC marker, OX-62. After depletion of plastic-adherent and Fc+ cells by panning on dishes coated with normal serum, residual BM cells were cultured in gelatin coated flasks using murine rGM-CSF supplemented medium. Prior to analysis, non-adherent cells were re-depleted of contaminating Fc+ cells. Propagation of DC was monitored by double staining for FACS analysis (major histocompatibility complex (MHC) class II+/OX-62+, OX-19-). Functional assay, morphological analysis and evaluation of homing patterns of cultured cells revealed typical DC characteristics. MHC class II and OX-62 antigen expression increased with time in culture and correlated with allostimulatory ability. DC yield increased until day 7, when 3.3 x 10(6) DC were obtained from an initial 3 x 10(8) unfractionated BM cells. Significant numbers of DC can be generated from rat BM using these simple methods. This should permit analysis and manipulation of rat DC functions in vivo and in vitro.

The biological basis of and strategies for clinical xenotransplantation

Recent discoveries have suggested that the exchange of multiple leukocyte lineages between grafts and host and subsequent long-term chimerism in both is the seminal mechanism of the acceptance of organs transplanted from the same (allografts) or different species (xenografts). This insight suggests new strategies which may allow xenotransplantation, the principal obstacle to which has been humoral rejection. We have defined humoral rejection as a family of complement activation syndromes afflicting allografts and xenografts in which there is a strong (but not invariable) association with performed antigraft antibodies, invariable evidence of complement activation, histopathologic stigmas of vascular endothelial damage, and a concomitant local or systemic coagulopathy. The generic descriptive term hyperacute rejection is a misnomer because a slow-motion version of the same "humoral" process can occur with some allografts and is the rule with the so-called concordant species xenotransplantations. The pathway of experience and discovery leading to this conclusion shows clearly that the distinction frequently made between allograft versus xenograft humoral rejection does not actually exist in principle, but only in details and intensity. Breaking down this barrier to xenotransplantation, whether or not it is associated with antibodies, is unrealistic. However, the possibility of avoiding the barrier has been exposed by showing that animal organs can be humanized, with a mixed donor and recipient cell population similar to the chimerism seen in long surviving allografts or even with complete leukocyte replacement. Pilot experiments in rodents suggest that organs from fully xenogeneic chimeras can be made into xenogeneic targets that are no more provocative of complement activation than allografts when they are transplanted into the donor bone marrow species. Although the validity of this concept of organ xenograft preparation is only at the pilot stage of verification, there is reason to suspect that the complement trigger of humoral rejection can be thereby disarmed. If this can be accomplished, independent evidence suggests that cellular rejection can be controlled with conventional T-cell directed immunosuppression, perhaps even with surprising ease. The potential subtle liability of synthetic products of xenogeneic parenchymal cells is not yet known.

Modified simple cold storage of rat livers with UW solution

Rat livers were preserved with the conventional use of UW solution for 30, 42, and 48 hr and compared with livers in which the vascular bed was expanded with an additional 10 to 60 ml UW/100 g liver. The extra UW, expressed as % liver weight, was entrapped during final portal infusion by typing off the supra- and infrahepatic inferior vena cava. A beneficial influence of the vascular expansion was most pronounced in the 40% group, with 10/10, 5/10, and 3/10 long-term survivors following transplantation after 30, 42, and 48 hr preservation versus 3/10 and 0/10 after 30 and 42 hr in the 0% controls. In separate experiments, surrogate indices of preservation quality following reperfusion explained this effect. The 40%--and, to a lesser extent, 20%--livers had higher and more uniformly distributed portal blood flow, better tissue oxygenation, smaller increases in postperfusion liver enzymes, higher adenine nucleotides and energy charge, and less histopathologic evidence of hemorrhage and congestion. Pressure changes in the vena cava fluid sump in additional experiments indicated that retrograde infusion of the trapped UW solution occurred in all of the 10-60% groups during the first 6 hr with stable pressures of 1.5 to 3 cm H2O thereafter. Collectively, these data suggest that the much discussed selective vulnerability of the microvasculature of stored allografts is due in part (or principally) to its selective lack of long-term exposure to the UW solution, which drains out of the open vessels but not from the parenchyma. The potential clinical exploitation of this concept is discussed.

Combined immunosuppressive therapy with low dose FK506 and antimetabolites in rat allogeneic heart transplantation

Following rat heterotopic heart allotransplantation, low to lethal doses of the antimetabolites mizoribine (MIZ), RS-61443 (RS), and AZA were given alone or in combination with subtherapeutic doses of FK506 (0.04 mg/kg/day) for 14 days after transplantation. With the median effect analysis of Chou and Kahan for quantitative drug interactions, substantial therapeutic synergism was demonstrated between FK506 and non-toxic doses of MIZ (2.5, 5, and 10 mg/kg/day) or AZA (5, 30, and 45 mg/kg/day), which was particularly evident with the lowest dose MIZ (2.5 mg/kg/day). When FK506 was used in combination with MIZ or AZA but not with RS, the maximum effect (peak median graft survival) was enhanced significantly from 15 days (MIZ alone) to 26 days (P < 0.05), and from 19 days (AZA alone) to 32 days (P < 0.01). In contrast, RS interacted with FK506 no more than additively. Although RS was the most powerful single antimetabolite, the best overall survival was obtained by combining AZA and FK506. The addition of FK506 did not significantly increase the percent mortality and LD50 of the antimetabolites.

Interferon-gamma induced expression of MHC antigens facilitates identification of donor cells in chimeric transplant recipients

After whole organ transplantation, donor bone marrow-derived cells migrate out of the graft into the recipient, leading to establishment of chimerism, which is the first step towards the subsequent induction of donor-specific tolerance. In routine immunohistochemical staining, monoclonal antibodies specific for heterotopic MHC alleles are used to identify donor and recipient cells. However, it is difficult to detect these cells using this technique in long-term allograft recipients who have a persistently low donor cell population (microchimerism). Because Interferon-gamma (IFN-gamma) is known to induce expression of MHC class I and class II cell surface molecules, we used this cytokine 12-48 h before sacrifice, to facilitate the identification of donor and recipient cells in the tissues of animals transplanted with either liver (B10-->C3H) or bone marrow (LEW-->BN). In long-term allograft recipients, the use of IFN-gamma for as briefly as 12 h prior to sacrifice, results in marked upregulation of class I and class II antigens, leading to easy identification of ubiquitously distributed low numbers of donor cells.

Effect of FK506 on rat Leydig cell function--in vivo and in vitro study

FK506, a macrolide antibiotic, is a potent immunosuppressant and has a biological effect similar to that of cyclosporin A (CsA). In this study, the in vivo and in vitro effects of FK506 on rat Leydig cell function were investigated. In vivo, basal testosterone levels and secretion in response to human chorionic gonadotropin (hCG) stimulation in ACl rats treated with intramuscular (IM) injections of FK506 at a dosage of 1 or 2 mg/kg/d for 14 days were not different from those of age-matched normal controls. Testicular weights (g) from rats treated with 14 injections of 1 mg/kg/d FK506 (1.08 +/- 0.08, n = 14) were similar to weights from age-matched controls (1.04 +/- 0.08, n = 14). Similarly, Wistar (Wi) rats treated with FK506 at a dosage of 1 mg/kg/d for 2 weeks showed basal testosterone and luteinizing hormone (LH) levels and secretion in response to hCG stimulation similar to those of normal controls. Histologically, the Leydig cells and germ cells in FK506-treated animals appeared normal. In vitro, basal testosterone production and response to hCG stimulation by both ACI and Wi rat Leydig cells exposed to overnight treatment of FK506 (10 to 1,000 ng/mL) were not significantly different from those of control Leydig cells. Furthermore, the viability of the Leydig cells cultured for 3 days in FK506 was not significantly different from that of controls, and they continued to secrete testosterone at a rate similar to that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Murine liver allograft transplantation: tolerance and donor cell chimerism

Nonarterialized orthotopic liver transplantation with no immunosuppression was performed in 13 mouse-strain combinations. Two strain combinations with major histocompatibility complex class I and class II and minor histocompatibility complex disparity had 20% and 33% survival of more than 100 days, but the other 11 combinations, including four that were fully allogeneic and all with only class I, class II or minor disparities, yielded 45% to 100% survival of more than 100 days. Long-living recipients permanently accepted donor-strain heterotopic hearts transplanted on the same day or donor-strain skin 3 mo after liver transplantation, in spite of detectable antidonor in vitro activity with mixed lymphocyte reaction and cell-mediated lymphocytotoxicity testing (split tolerance). In further donor-specific experiments, liver grafts were not rejected by presensitized major histocompatibility complex class I-disparate recipients and they protected donor-strain skin grafts from second set (or any) rejection. Less frequently, liver transplantation rescued rejecting skin grafts placed 1 wk earlier in major histocompatibility complex class I, class II and minor histocompatibility complex, class II or minor histocompatibility complex-disparate strain combinations. Donor-derived leukocyte migration to the central lymphoid organs occurred within 1 to 2 hr after liver transplantation in all animals examined, persisted in the surviving animals until they were killed (> 375 days), and was demonstrated with double-immunolabeling to be multilineage. The relation of these findings to so-called hepatic tolerogenicity and to tolerance in general is discussed.

Successful islet allotransplantation in diabetic rats immunosuppressed with FK506: a functional and immunological study

The effect of a novel immunosuppressive agent, FK506, on fresh islet allografts was evaluated in diabetic rats across major histocompatibility complex (MHC) barriers with respect to the transplantation (TR) site, islet source, treatment regimen, and antidonor antibody (Ab) titers of the recipients after TR. The functional periods of Wistar (Wi) islets transplanted under kidney capsule (KC) or intraportally (IPo) and of a mixture of Wi and Lewis (Le) islets under KC or IPo in nonimmunosuppressed ACI rat recipients were 6.9 +/- 0.4 (n = 7), 6.4 +/- 0.5 (n = 7), 5.6 +/- 0.4 (n = 7), and 6.2 +/- 0.4 (n = 5) days, respectively. FK506 treatment at 1 mg/kg/d intramuscularly (IM) for 2 weeks (protocol I) following islet TR under KC and IPo significantly prolonged the allograft function to more than 71.8 +/- 11.3 (n = 10) and 161.7 +/- 18.6 (n = 11) days, respectively. Additional treatment with FK506 at 1 mg/kg/wk (protocol II) further increased the islet survival under KC to more than 212.6 +/- 22.3 (n = 8) days. With this FK506 treatment protocol, the Wi + Le mixed-islet allograft function was extended to more than 106.1 +/- 10.5 (n = 7) and 167.9 +/- 28.6 (n = 7) days under KC and IPo, respectively. Nephrectomy in 8/8 ACI rats with long-term-functioning Wi (n = 6) and Wi + Le (n = 2) islet allografts resulted in their return to hyperglycemia. Immunohistochemical staining showed abundant insulin-positive cells at the graft site, with small numbers of CD4- and CD8-positive cells present in the vicinity of the normal-appearing islets. Macrophages were not detected.(ABSTRACT TRUNCATED AT 250 WORDS)