Detection of interstitial increase in macrophages, characteristic of acute interstitial rejection, in routinely processed renal allograft biopsies using the monoclonal antibody KP1

Expression of CTL associated transcripts precedes the development of tubulitis in T-cell mediated kidney graft rejection

The usual phenotype of clinical kidney allograft rejection is infiltration by lymphocytes and macrophages and evolution of histologic Banff lesions, particularly tubulitis, which indicate parenchymal injury. Using Affymetrix microarrays, we evaluated the relationship between the evolution of pathologic lesions and the transcriptome. We studied CBA/J into C57Bl/6 mouse kidney allografts in which one host kidney is left in place to permit observation of lesion development. Histology was dominated by early infiltration by mononuclear cells from day 3 and slower evolution of tubulitis after day 7. We defined a set of cytotoxic T lymphocyte-associated transcripts (CATs) on the basis of expression in purified cytotoxic T lymphocytes (CTL) and in a mixed lymphocyte culture, and absence in normal kidney. CATs were detectable by day 3 and highly expressed by day 5 in rejecting kidneys, with a median signal 14% of that in CTL, compared to 4% in isografts and normal kidneys, and persisted through day 42. Lack of mature B cells had little effect on CAT expression, confirming that CATs reflect T-cell-mediated rejection. Expression of CATs was established before diagnostic lesions and remained remarkably consistent through day 42 despite massive alterations in the pathology, and probably reflects T cells recruited to the graft.

Monocytes-macrophages and cytokines/chemokines in fine-needle aspiration biopsy cultures: enhanced interleukin-1 receptor antagonist synthesis in rejection-free kidney transplant patients

BACKGROUND

Monocytes-macrophages are found within kidney allografts during the first days after surgery, where they perform "housekeeping" tasks, participate in postreperfusion injury, and act as antigen-presenting cells, as well as become involved in the effector phase of acute rejection. They also seem to play a prominent role in chronic rejection. We quantified their presence in fine-needle aspiration biopsies and studied the growth factors that, we hypothesized, would mark the different implications of the presence of monocytes-macrophages.

METHODS

Fine-needle aspiration biopsies were obtained from 56 adult renal transplants and analyzed for CD14+ using the alkaline phosphatase-anti-alkaline phosphatase procedure. Thirty-three patients were studied on the production of interleukin (IL)-1 receptor antagonist (IL-1ra), IL-6, IL-8, macrophage colony-stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1alpha by aspiration biopsies cultures using enzyme-linked immunosorbent assay techniques.

RESULTS

CD14+ cells were present at significantly higher numbers in steroid-resistant acute rejections but also during the first days after surgery, especially if acute tubular necrosis was present. We found a significantly higher production of IL-1ra by rejection-free patients compared with acutely rejecting patients, and this difference was already established on day 7 after surgery (10+/-10.5 days before rejection).

CONCLUSIONS

Monocytes-macrophages are present at higher numbers in aspiration biopsies of kidney transplant patients suffering either acute tubular necrosis or steroid-resistant rejections, but they are present during the first days after transplant in stable patients, too. The production of IL-1ra is significantly up-regulated in stable patients, which suggests that monocytes-macrophages may constitute an early key factor in the down-regulation of the anti-allograft immune response.

Monocyte chemotactic peptide-1 expression and monocyte infiltration in acute renal transplant rejection

Mononuclear cell infiltration is a common histopathological feature of acute renal transplant rejection, in which it seems to play a key role in the pathogenesis of tubulointerstitial lesions. Monocyte chemotactic peptide-1 (MCP-1) is a specific chemotactic and activating factor for monocytes. Thus, the present study was aimed at evaluating MCP-1 gene and protein expression in renal biopsies of kidney transplant recipients with acute deterioration of graft function, and to correlate it with the extent of monocyte infiltration. We studied 20 kidney transplant recipients with acute graft dysfunction (13 with acute rejection, seven with acute tubular damage). MCP-1 gene and protein expression were analyzed by in situ hybridization and immunohistochemistry, respectively. CD68-positive cells were identified as monocytes. CD68-positive cell number and MCP-1 expression were quantified by a computerized image analysis system. MCP-1 gene expression, undetectable in normal human kidneys, was strikingly increased in patients with acute rejection. The chemokine localized mainly to the proximal tubular cells and to mononuclear-infiltrating cells. In patients with acute tubular damage, the MCP-1 expression, even if higher than in controls, was significantly lower than in acute rejection. The expression of the chemokine strictly correlated with the number of infiltrating monocytes (r=0.87, P<0.05). Moreover, we measured MCP-1 urinary excretion by ELISA, in eight normal subjects (36+/-16 pg/mg urine creatinine), in 13 clinically stable transplant recipients (33+/-9 pg/mg, ns vs. normal patients), in 12 transplant recipients with acute rejection (250+/-46 pg/mg, P<0.01 vs. normal patients), and in five transplant recipients with acute tubular damage (97+/-33 pg/mg, P<0.05 vs. controls and patients with acute rejection). Urinary MCP-1 excretion directly correlated with renal MCP-1 gene expression (r=0.65, P=0.05). Finally, we observed a significant reduction in MCP-1 urine levels in patients with acute rejection, who responded to the antirejection treatment. In conclusion, our data suggest that MCP-1 may play a critical role in modulating monocyte influx and consequent tubulointerstitial damage in acute rejection. Therefore, an increase in urinary MCP-1 excretion may represent an early signal of ongoing acute graft rejection.

A practical approach to the diagnosis of renal disease by biopsy

The pathologist has an important role in the diagnosis and monitoring of renal disease. However, for optimal useful information to be derived from renal biopsy specimens, certain guidelines must be adhered to and these are enunciated here. The 3 avenues of observation of renal biopsies viz. light microscopy, immunofluorescence and electron microscopy, all have important roles to play and give differing data which informs the diagnosis for the renal biopsy report. The relative emphasis on each of these modalities of investigation will vary depending upon the situation in which the renal biopsy is performed. The methods used here have been shown to be effective in practice over a period of 20 yrs. Although there may be variations in methodology from centre to centre, the general background aims and principles remain the same. The emphasis in this paper has been on common practical aspects of renal biopsies. Much of the practical information concerning renal biopsies, which is brought together here, is otherwise scattered and not readily available. The aim of this article is to allow the reader to understand the rationale for the steps that are involved in renal biopsy diagnosis.