Alyssa M. Krasinskas

Non-hematopoietic allograft cells directly activate CD8+ T cells and trigger acute rejection : an alternative mechanism of allorecognition

Despite evidence that human non-hematopoietic cells, such as vascular endothelium, can activate allogeneic T lymphocytes in vitro, the prevailing view has been that hematopoietic antigen-presenting cells are required to trigger alloimmune responses in vivo. Here we report that mouse non-hematopoietic cells activate alloreactive CD8+ T lymphocytes in vitro and in vivo. We also show that vascularized cardiac allografts are acutely rejected via CD8+ direct allorecognition even if the alloantigen is not presented by hematopoietic professional antigen-presenting cells. Because activation of alloreactive CD8+ T cells by donor-type non-hematopoietic cells can continue for the life of the allograft, these findings present a new clinically relevant mechanism of allorecognition and should be taken into consideration when developing strategies to prevent allograft vasculopathy or to induce tolerance.

Kikuchi-Fujimoto disease: A benign cause of fever and lymphadenopathy

PURPOSEnTo describe 6 cases of Kikuchi-Fujimoto disease and to review the literature.nnnPATIENTS AND METHODSnReview of 6 patients with biopsy-proven Kikuchi-Fujimoto disease detected at a university hospital over a 5-year period.nnnRESULTSnSix patients presented with localized, mild lymph node enlargement. In 3 cases, dramatic fever, chills, weight loss and systemic complaints were present. These features prompted prolonged antibiotic therapy and extensive evaluations of fever of unknown origin before the diagnosis was made by biopsy of the minimally enlarged lymph nodes. The 3 remaining patients were otherwise asymptomatic and well. All 6 subjects recovered without specific therapy.nnnCONCLUSIONSnKikuchi-Fujimoto disease is a recently described cause of benign, self-limited lymphadenopathy that is easily confused histologically and clinically with lymphoma and systemic lupus erythematosis. Clinicians and pathologists must be aware of this condition. Although it is an uncommon cause of fever of unknown origin, early recognition of KFD will minimize potentially harmful and unnecessary evaluations and treatments.

Vascular Endothelium Does Not Activate CD4+ Direct Allorecognition in Graft Rejection

Expression of MHC class II by donor-derived APCs has been shown to be important for allograft rejection. It remains controversial, however, whether nonhemopoietic cells, such as vascular endothelium, possess Ag-presenting capacity to activate alloreactive CD4+ T lymphocytes. This issue is important in transplantation, because, unlike hemopoietic APCs, allogeneic vascular endothelium remains present for the life of the organ. In this study we report that cytokine-activated vascular endothelial cells are poor APCs for allogeneic CD4+ T lymphocytes in vitro and in vivo despite surface expression of MHC class II. Our in vitro observations were extended to an in vivo model of allograft rejection. We have separated the allostimulatory capacity of endothelium from that of hemopoietic APCs by using bone marrow chimeras. Hearts that express MHC class II on hemopoietic APCs are acutely rejected in a mean of 7 days regardless of the expression of MHC class II on graft endothelium. Alternatively, hearts that lack MHC class II on hemopoietic APCs are acutely rejected at a significantly delayed tempo regardless of the expression of MHC class II on graft endothelium. Our data suggest that vascular endothelium does not play an important role in CD4+ direct allorecognition and thus does not contribute to the vigor of acute rejection.

A simple method for culturing mouse vascular endothelium.

Vascular endothelium is an important site for a wide array of immunological processes such as inflammation, atherosclerosis and allograft rejection. Culture methods of mouse vascular endothelium would provide an important in vitro correlate to immunological murine in vivo models. We describe a simple method to culture mouse vascular endothelium from thoracic aorta. Our cultured cells express typical phenotypic (CD105, CD31, CD106), morphological and ultrastructural (intercellular junctions, Weibel-Palade bodies) markers of vascular endothelium. They also possess functional receptors for uptake and processing of acetylated low-density lipoproteins. The mouse vascular endothelium within our system expresses high levels of MHC class I and MHC class II after activation with IFN-gamma. In addition, these cells express the accessory molecules CD80 and CD54, while they lack constitutive expression of CD86 and CD40, providing them the means to function as antigen presenting cells. Alloreactive CD4(+) and CD8(+) T lymphocytes demonstrate evidence of DNA synthesis after co-culture with activated vascular endothelium indicating their commitment to proliferation. In conclusion, we describe a simple culture system to isolate and grow mouse vascular endothelium, which provides a powerful tool to study biological interactions in vitro.

CD3 monitoring of antithymocyte globulin therapy in thoracic organ transplantation.

Background. Antithymocyte globulin is frequently used as a component of induction therapy in thoracic organ transplantation. This study evaluates the utility of monitoring peripheral CD3 lymphocytes to rationally adjust antithymocyte globulin therapy in this patient population. Methods. A total of 17 heart and 19 lung transplant recipients received antithymocyte globulin (ATGAM or thymoglobulin) as induction therapy or to treat steroid-resistant acute or chronic rejection. Absolute CD3 counts were maintained between 50 and 100 cells/&mgr;l. Results. With CD3 monitoring, the doses of antithymocyte globulin were reduced from 10–15 mg/kg to 1–5 mg/kg during the course of therapy. The total amount of antithymocyte globulin given to each CD3 monitored patient was reduced by 48%. Dose reduction did not alter the number of acute rejection or infectious episodes, and hematological side effects were infrequent. Conclusion. CD3 monitoring of antithymocyte globulin therapy in thoracic organ recipients reduced the amount of drug received by each patient, while maintaining CD3 counts less than 100 cells/&mgr;l.

Depletion of recipient CD4+ but not CD8+ T lymphocytes prevents the development of cardiac allograft vasculopathy

Background. We have described that chimeric rat hearts bearing recipient-type antigen-presenting cells (APCs) do not reject acutely, but develop cardiac allograft vasculopathy (CAV) in untreated recipients. This suggests that CAV is triggered either by CD8+ direct allorecognition or by CD4+ indirect allorecognition. To determine the allorecognition pathway responsible for CAV in this model, recipients of chimeric hearts underwent either CD8+ or CD4+ T cell depletion. Methods. Chimeric hearts were created via bone marrow transplantation in two fully major histocompatibility-mismatched rat strain combinations. DA recipients were thymectomized and treated with Ox8 and Ox38 murine monoclonal antibodies, which deplete CD8+ and CD4+ T cells, respectively. Chimeric PVG hearts bearing DA APCs, abbreviated PVG(DA), were heterotopically transplanted into recipients undergoing thymectomy alone or recipients undergoing thymectomy plus either CD4+ or CD8+ T cell depletion. Results. PVG(DA) allografts survived 100 days, but developed CAV in thymectomized recipients and in those permanently depleted of CD8+ T cells. In contrast, chimeric hearts transplanted into permanently CD4+ T cell-depleted recipients survived 100 days and demonstrated no evidence of CAV. Conclusions. In this specific strain combination, recipient CD8+ T cells are neither necessary nor sufficient for the development of CAV, whereas recipient CD4+ T cells are required for the development of CAV. These findings suggest that CAV is dependent on CD4+ indirect allorecognition and that CD8+ direct allorecognition stimulated by nonprofessional APCs plays a minor role.

Immune monitoring in xenotransplantation: The multiparameter flow cytometric mixed lymphocyte culture assay

Xenotransplantation requires monitoring of complex cellular interactions in vitro. A tool to monitor cell proliferation in detail would be instrumental in understanding these cellular interactions in heterogeneous xenogeneic lymphocyte cultures and in patients after xenotransplantation. To accomplish this, we used a fluorescent cell proliferation marker, 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE), in combination with flow cytometry. CFSE, a green fluorescent molecule, binds covalently to intracellular macromolecules. Each cell division reduces the fluorescent intensity per cell by half and shows a characteristic multipeak pattern in flow cytometric analysis. For this study, human lymphocytes were labeled with CFSE and cultured in the presence of irradiated porcine lymphocytes. Cell proliferation was detected in CFSE-labeled lymphocytes in both a single and a multiparameter flow cytometry setting. Concurrently, tritiated ((3)H) thymidine incorporation, a common method to measure gross cell proliferation, was assessed. The kinetics of CFSE-labeled cell proliferation correlated with (3)H-thymidine incorporation in that both methods showed a lag phase for days 1-3 and a log phase for days 4-7. Multiparameter flow cytometric monitoring of mixed lymphocyte cultures allowed phenotyping and assessment of viability of proliferating populations in heterogeneous xenogeneic stimulated human lymphocyte cultures and complemented the classical (3)H-thymidine incorporation assay. The use of this technique will allow a wide array of immunologic parameters to be measured in a heterogeneous xenogeneic mixed lymphocyte culture. The information gained from these assays is essential to understanding the biological significance of xenogeneic cellular interaction and for monitoring the immune status of the xenotransplanted patient.

Oxyntic mucosa pseudopolyps: A presentation of atrophic autoimmune gastritis

Gastric polyps are often present in the setting of atrophic gastritis. Although the majority of these polyps are nonneoplastic, such as hyperplastic polyps, neoplastic polyps may be present. We discuss nine cases that illustrate an additional nonneoplastic cause of polyps in atrophic gastritis. Specifically, preserved islands of relatively normal oxyntic mucosa in a background of gastric atrophy may appear polypoid endoscopically. The patients (seven women, two men, mean age 64 years) presented with nonspecific abdominal or reflux symptoms (n = 8) and diarrhea (n = 1). Five of five patients tested were confirmed to have hypergastrinemia, and three of three patients tested had antiparietal cell antibodies. Biopsies from the gastric body or fundus of our nine patients showed fragments of atrophic mucosa and separate fragments of preserved oxyntic mucosa. Based upon the histologic characteristics of the atrophic fundic and relatively normal antral biopsies, the gastric atrophy appeared to be of autoimmune-type. The relatively preserved oxyntic glands showed parietal cell hypertrophy and focal mild chronic inflammation. The number of polyps observed endoscopically ranged from less than five to multiple/diffuse. Three patients had persistent nodularities in their stomachs for 1, 3, and 7 years of their follow-up. Our study shows that some patients with atrophic gastritis, autoimmune-type, may present with gastric polyps/nodules that represent relatively preserved oxyntic mucosa. This presentation may be more common than is presently recognized because biopsies of the polyps alone will not show histologic features of atrophic gastritis or reveal the etiology of the polyp itself. Although a limited number of previous studies have suggested this type of polypoid presentation may represent “early” atrophic gastritis, its persistence in three of our patients argues against this hypothesis.

The role of passenger leukocyte genotype in rejection and acceptance of rat liver allografts.

Background. Although graft-resident passenger leukocytes are known to mediate acute rejection by triggering direct allorecognition, they may also act in an immunomodulatory fashion and play an important role in tolerance induction. Our purpose in the current study was to utilize rat bone marrow chimeras to evaluate the role of the genotype of passenger leukocytes in both acute rejection and tolerance of liver allografts. Methods. The fate of livers bearing donor-type, recipient-type, and third-party passenger leukocytes was evaluated in the MHC class I and II mismatched rejector combination ACI→LEW and the acceptor combination PVG→DA. Results. We report that although treatment of ACI liver donors with lethal irradiation does not lead to prolongation of graft survival in the ACI→LEW strain combination, ACI livers bearing recipient-type (LEW) or third-party passenger leukocytes (BN) are rejected at a significantly slower rate. We confirm that lethal irradiation of PVG donor animals leads to abrogation of tolerance induction with acute rejection of their livers by DA recipients. However, the majority of PVG livers carrying donor-type (PVG), recipient-type (DA), or third-party (LEW) passenger leukocytes are accepted for >100 days. These DA recipients develop immune tolerance to the donor parenchyma (PVG). Conclusions. Our findings demonstrate that long-term acceptance of liver allografts and tolerance induction is not dependent on the presence of donor-type passenger leukocytes and can be achieved with organs carrying donor-type, recipient-type, or third-party passenger leukocytes. The importance of the MHC framework on the surface of passenger leukocytes as a critical regulator of the immune response after transplantation of chimeric organs is substantiated by the delayed tempo of rejection of ACI livers bearing recipient-type or third-party passenger leukocytes in the ACI→LEW strain combination.

Emergent lung retransplantation after discovery of two primary malignancies in the donor.

A 50-year-old woman underwent single lung transplantation for advanced chronic obstructive pulmonary disease. Shortly after the procedure, it was discovered that the donor suffered from both a renal cell carcinoma and a spindle-cell sarcoma of the ascending aorta, which had metastasized to the spleen. The patient was emergently listed for a retransplantation and underwent bilateral lung transplantation after a new donor became available 4 days after the initial transplantation procedure. After 24 months, the patient is without evidence of malignancy. This case illustrates the role of immediate retransplantation for patients who have inadvertently received thoracic organs from donors harboring occult malignancies.