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Case Report |
Address correspondence to Ping L. Zhang, MD, PhD, Dept. of Laboratory Medicine, Geisinger Medical Center, 100 N. Academy Ave., Danville, PA 17822, USA; tel 570 271 6333; fax 570 271 6105; e-mail: plzhang{at}geisinger.edu.
Abstract
Campath-1H (alemtuzumab), a humanized monoclonal antibody against CD52, can cause more profound depletion of lymphocytes than monocytes. The resultant imbalance of lymphocytes and monocytes after Campath-1H treatment of a renal-transplant recipient may lead to an acute rejection dominated by monocytes. We report such a case of acute transplant rejection in a 49-yr-old man who received a living non-related kidney transplant and was treated with preoperative Campath-1H and postoperative immunosuppression. An initial post-transplant renal biopsy showed diffuse mild acute rejection with 95% CD68-positive monocytes, but only 5% CD3-positive T lymphocytes. Inflammatory cells in the renal biopsy were negative for CD34 and CD1a stains, suggesting non-involvement of CD34-derived dendritic cells in the acute rejection. After steroid treatment for 2 wk, the patient’s serum creatinine concentration diminished to 1.5 mg/dl. The histopathological features of acute rejection were absent in a second biopsy of the transplanted kidney. In summary, this case is an instance of monocyte-mediated acute rejection of a transplanted kidney.
(received 13 January 2004; accepted 24 January 2004)
Keywords: Campath-1H, CD52, monocytes, acute transplant rejection, renal transplantion
Introduction
In 1998, Calne et al [1] reported that peri-operative Campath-1H induction and postoperative cyclosporin maintenance resulted in a low rejection rate in 13 renal-transplant recipients. Kirk et al [2] confirmed the effectiveness of pretreatment with Campath-1H, in suppressing acute rejection in 7 renal recipients of living-donor kidneys. However, administration of Campath-1H alone was associated with monocyte-associated acute rejection, which was treated with steroids [2]. Monocyte-mediated acute rejection after treatment with Campath-1H alone has been reported in bone marrow transplant recipients [3,4]. A recent study reported a low rejection rate in renal transplant recipients who received preoperative treatment with antithymocyte globulin to deplete T lymphocytes and postoperative administration of a low dose of tacrolimus (FK506), an immunosuppressive agent [5].
During the past 8 months, we have performed 30 renal transplants with preoperative induction of tolerance using Campath-1H and postoperative immunosuppression. In this series, we have observed one clinically significant instance of acute transplant rejection, which is the subject of this report.
Case Report
A 49-yr-old man with end-stage renal disease secondary to Goodpasture’s syndrome received a living non-related kidney transplant from a 41-yr-old man. The patient was treated iv with 30 mg Campath-1H (alemtuzumab, Millennium Pharmaceuticals, Cambridge, MA), 30 min before the renal transplantation. The donor kidney was transplanted successfully and the recipient’s serum creatinine concentration diminished remarkably (Table 1
). After surgery, the patient was treated with maintenance therapy of mycophenolate mofetil (CellCept). In addition, he received 20 mg of prednisone daily.
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). At the second week after the transplant, the patient developed an elevated serum creatinine concentration and a rise in the percentage of blood monocytes, while the blood lymphocytes remained very low. Acute rejection was suspected and an initial biopsy of the transplanted kidney was performed at 14 days after surgery. The initial renal biopsy was fixed in formalin and paraffin embedded. The tissue block was cut into 5 µm sections and underwent routine staining for renal biopsies (3 sections for hematoxylin-eosin stain, 3 sections for periodic acid-Schiff stain, and 1 section for Masson trichrome stain). In addition, five immunohistochemical stains were performed. The primary antibodies (CD3, CD68, CD20, CD34, and CD1a) and secondary antibodies were all obtained from DAKO Corp. (Carpinteria, CA). Sections were dewaxed in xylene and rehydrated with graded ethanol:water solutions. Immunohisto-chemical staining for the various markers was performed with an autostainer (Model E172566, DAKO Corp.).
The renal biopsy showed 8 unremarkable glomeruli, but diffuse infiltration of inflammatory cells in the interstitium (Fig. 1A). Tubulitis was relatively mild, consisting of 4 inflammator y cells per tubular cross section. This finding was consistent with mild diffuse acute rejection (Banff Criteria Ib). Approximately 95% of the inflammatory cells were positive for CD68, indicating primarily monocytes (Fig. 1B). Only about 5% of inflammatory cells were positive for CD3, consistent with T lymphocytes (Fig. 1C). All inflammatory cells were negative for CD20, indicating non-involvement of B lymphocytes in the acute rejection. The inflammatory cells were also negative for CD34 and CD1a, suggesting non-involvement of CD34-derived dendritic cells in the acute rejection. No vasculitis was identified in the biopsy.
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). A second follow-up biopsy, performed 2 wk later, showed 2 unremarkable glomeruli. No significant inflammatory cells or tubulitis was present, but mild acute tubular injury was noted (Fig. 1D). The renal parenchyma was well maintained and vascular abnormalities were not evident. Discussion
T lymphocytes are conventionally known to mediate acute rejection of renal transplants [6]. Antigen-presenting cells (also called dendritic cells) bring antigens to T cell receptor complex (composed of CD3 isoforms 
, ß,
, 
and 
). This interaction triggers 2 effects in cytotoxic T cells (CD8 positive). First, a secretory pathway involves granule-mediated exocytosis of soluble factors, including granzymes (serine esterases), and a complement-like molecule, perforin. These proteins induce cell death via both DNA degradation and osmotic lysis secondary to pore formation in the target cell membrane. Second, a cytolytic pathway involves interaction between Fas (CD95), a tumor necrotizing factor-like protein, and Fas ligand via triggering of the T cell receptors. Fas-expressing target cells such as renal tubular epithelial cells undergo apoptosis when Fas ligand induced on T lymphocytes is engaged.
The role of monocytes in animal models of acute rejection has been reported [7,8]. In humans, approximately 34% (1000 to 4800/µl) of white blood cells are lymphocytes, but only 4% (0 to 800/µl) of white blood cells are monocytes in healthy adults. After conventional renal transplantation and postoperative immunosuppression, effects of monocytes during acute rejection may be overshadowed by the predominant presence of T lymphocytes in the grafts during acute rejection.
Monocytes were first found to be significantly higher in fine-needle aspirates of renal transplants with steroid-resistant acute rejection [9]. Recently, effects of monocyte-mediated acute rejection were found in 7 renal transplants with preoperative Campath-1H treatment (100% of cases in the first mo after transplant) [2]. Since Campath-1H can more profoundly deplete T lymphocytes than monocytes, this study of renal recipients with Campath-1H treatment uncovered the effects of CD68-positive monocytes as a dominant population of inflammatory cells involved in acute rejection.
Using antithymoglobulin to induce tolerance and postoperative immunosuppression in various types of graft transplantation, Starzl et al [5] found that the depletion of T cells was greater than that of monocytes. The combination therapeutic regimen was associated with 46% of acute rejection (23/50 renal transplants) in the first mo after transplantation. The possible involvement of monocytes in the acute rejection was not investigated in that study [5].
In the current report, our patient developed monocyte-mediated acute rejection within 2 weeks despite preoperative Campath-1H induction and postoperative immunosuppression. This case is the only instance of acute rejection proven by pathologic examination in our series of 30 renal transplants during 8 mo of follow-up. Two additional mild acute rejections (Ia) with 80% monocytes and 20% T lymphocytes were incident-ally found in protocol biopsies from 2 patients at 3 and 5 mo after renal transplantation (unpublished data). Although the monocyte infiltration appeared diffuse, tubulitis was focally identified. This finding supports the observation that monocytes may injure renal tubules via cytokine-mediated toxicity (such as IL-10, TNF-, and interferon-), rather than a direct attack by T lymphocytes [2].
Among monocytes, a relatively small percentage comprises monocyte-derived dendritic cells. Dendritic cells are the most potent antigen-presenting cells and the most critical in regard to initiation of cellular immune responses. Normal peripheral blood contains at least 2 dendritic cell subsets that together make up 0.01 to 0.1% of circulating leukocytes [10]. These 2 subsets include myeloid dendritic cells (CD34 hematopoietic progenitor cell-derived Langerhans cells, dermal interstitial dendritic cells, and monocyte-derived dendritic cells) and a lymphoid subset [10].
The first biopsy in the current report showed negative CD20 staining but focal CD3 positivity in approximately 5% of inflammatory cells, indicating a rare chance for lymphoid dendritic cells participating in the acute rejection. Since motile CD34 hematopoietic progenitor cell-derived Langerhans cells and dermal-interstitial dendritic cells were found to be resistant to Campath-1H treatment [3,4], the preservation of these cells after Campath-1H treatment may allow these myeloid dendritic cells to play formative roles in the redevelopment of acquired immunity. However, in our case, the inflammatory cells in the first biopsy were entirely negative for CD34 and CD1a, ruling out the possibility that motile CD34-originated dendritic cells contributed to the acute rejection. In contrast, 90% of the inflammatory cells were positive for CD68, indicating dominant involvement of monocytes and most likely some monocyte-derived dendritic cells (wavy CD68-positive cells morphologically) in the acute rejection.
Finally, the acute rejection, chiefly mediated by monocytes, responded rapidly to steroid treatment (Fig. 1D). The clinical and pathologic improvement following steroid treatment was consistent with the findings of Kirk et al [2]. In addition, Starzl et al [5] also found effectiveness of steroids in acute rejection cases after combined preoperative induction and postoperative immunosuppression. Therefore, the presence of monocytes in rejected grafts may not necessarily be a sign of steroid resistance observed by fine-needle aspiration of renal transplants [9]. Since CD20-positive B cell infiltration during renal rejection appears to be associated with steroid resistance [11], our finding of negative CD20 staining in inflammatory cells was consistent with a good response to steroid treatment in this case.
In summary, a case of acute renal rejection is described with infiltration mainly by CD68-positive monocytes. This acute rejection occurred in a renal recipient who received both preoperative Campath-1H induction and postoperative immuno-suppression. Blood monocytes were depleted, as were T lymphocytes, but monocytes regained a high percentage within 1 wk while lymphocytes remained low for a longer time. Acute renal rejection was suppressed by 2 wk of prednisone treatment.
Acknowledgment
The authors thank Ms. Kathy A. Fenstermacher for secretarial assistance.
References
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