Normal Human Kidney HLA-DR–Expressing Renal Microvascular Endothelial Cells

Abstract

Abstract. Human, but not murine, renal peritubular and glomerular capillaries constitutively express class II major histocompatibility (MHC) proteins at high levels in normal human kidney. Expression of class II proteins on renal microvascular endothelial cells (RMEC) makes it available to circulating lymphocytes and imparts a surveillance capacity to RMEC for controlling inflammatory responses. In this report, the coexpression of HLA-DR and the endothelial marker CD31 are used to identify RMEC as a distinct population of cells within a standard renal biopsy using flow cytometry. A three-laser, multicolor flow cytometry analysis using Alexa dyes, developed for characterizing the expression of cell surface antigens, identifies RMEC as a population separate from HLA-DRexpressing leukocytes. HLA-DR RMEC co-express HLA-DP and HLA-DQ. RMEC also express the T cell costimulatory factor CD58 but not CD80, CD86, or CD40. On the basis of high HLA-DR expression, RMEC are isolated for culture using fluorescence-activated cell sorting and magnetic beads. Cultured RMEC require normal basal physiologic concentrations of gamma interferon (␥IFN) to maintain HLA protein expression. This expression is regulated by CIITA, the MHC class II-specific transcription factor. Four tissue-specific promoters have been described for CIITA. In freshly isolated RMEC, RT-PCR and hybridization using specific oligonucleotide probes to CIITA promoter sequences identify only the statinsensitive ␥IFN-induced promoter IV of CIITA. Therefore, the constitutive expression of HLA-DR on RMEC in normal human kidney is located in a position for immune surveillance, depends on basal physiologic concentrations of ␥IFN, and may be amenable to regulation with statins.MHC proteins are of two classes distinguished on the basis of structure and function. Class I molecules, composed of a polymorphic subunit complexed with ␤-2-microglobulin, are found on all nucleated cells and present antigenic peptides to CD8ϩ T lymphocytes; class II molecules, composed of polymorphic ␣ and ␤ chains, are constitutively expressed on a limited number of cell types (dendritic cells, macrophages, B lymphocytes) and present antigenic peptides to CD4 ϩ T lymphocytes. We recently described an unusual expression of MHC class II proteins in normal human kidneys that is not found in murine kidneys (1). The human MHC class II protein HLA-DR is abundantly expressed on peritubular and glomerular capillary endothelial cells but not on endothelial cells of larger blood vessels of normal kidney. Antibodies to HLA-DR and CD31, a protein highly expressed on endothelial cells, co-localize on peritubular and glomerular cells within sections of kidney tissue, indicating capillary endothelial cell location of HLA-DR. HLA-DR has also been identified on rare scattered circulating leukocytes found within the kidney, but over 98% of the DR identified by immunofluorescence microscopy in kidney cortex is located on capillary endothelial cells (1). We refer to these cells co-expressing HLA-DR and CD31 as rena...

Retransplant candidates have donor-specific antibodies that react with structurally defined HLA-DR,DQ,DP epitopes

“…The correlation between antibody absence and a low number of mismatched DRB1 eplets (Table 3) suggests many DR antigen mismatches may have a limited potential of inducing a humoral immune response. Another explanation for the low detection rate of circulating anti-HLA-DR antibodies is that they have been absorbed by the allograft which has been shown to express HLA-DR antigens on its endothelium and parenchymal cells [45][46][47][48] and that DRB antibodies can be eluted from rejected transplants [49]. Moreover, anti-DRB antibodies are more readily detected in class II sensitized patients in the absence of a transplanted organ (Table 2), and their frequency of antibody detection is similar to that of HLA-DQ.…”

Characteristics, Detection, and Clinical Relevance of Alloantibodies in Kidney Transplantation

“…Interestingly, as was later reported by Müller, these cells lack HLA-DQ and HLA-DP antigens (Müller et al, 1989). Muczynski and colleagues, using three-laser multicolor FC analysis, have demonstrated the co-expression of HLA-DR, -DQ, and -DP proteins in renal microvascular cells (Muczynski et al, 2003). Subsequent studies have shown that all class II genes are expressed, whether constitutively or upon induction, at the following levels in decreasing order: DR>DP>DQ (Guardiola & Maffei, 1993).…”

“…Subsequent studies have shown that all class II genes are expressed, whether constitutively or upon induction, at the following levels in decreasing order: DR>DP>DQ (Guardiola & Maffei, 1993). In addition, the degree of cell surface expression largely depends on the cytokine milieu, particularly TNF and IFN as well as the activity of the CIITA (class II, major histocompatibility complex, transactivator) transcription factor (Guardiola & Maffei, 1993;Muczynski et al, 2003). The impact of promoter activity on the haplotype expression of HLA class II DRB1-DRB3, DRB1-DRB4, and DRB1-DRB5 has been investigated by Vincent and colleagues.…”

Soluble CD30 and Acute Renal Allograft Rejection

“…This group of genes resides on chromosome 6 and encodes cell-surface antigenpresenting proteins and many other proteins. HLA antigens on the cell membrane play an important role in the immune response to foreign tissue (Muczynski KA et al 2003). HLA complex is highly polymorphous (Marsh SG et al 2002).…”

“…In order to increase the matching rates, HLA typing has been recommended supported by the public epitope theory. MHC molecules are divided into 2 main classes: HLA class I antigens (HLA-A, HLA-B, HLA-C) are presented on the surface of all nucleated cells and platelets and HLA class II antigens (HLA-DR, HLA-DQ, HLA-DP, HLA-DM, HLA-DO) are expressed on professional antigen-presenting cells, but also on the surface of endothelial vascular cells and renal tubular epithelial cells (Muczynski KA et al 2003). Human capillary endothelial cells, in contrast to rodents, express both human lymphocyte antigen (HLA) class I and class II molecules with high density even under normal physiological conditions (McDouall RM.…”