Vascular and renal distribution of HLA--DR-like antigens

Insights gained from single-cell RNA analysis of murine endothelial cells in aging hearts

Aging is the strongest risk factor for cardiovascular disease, with progressive decline in the function of vascular endothelial cells (ECs) with age. Systematic analyses of the effects of aging on different cardiac EC types remain limited. Here, we constructed a scRNA atlas of EC transcriptomes in young and old mouse hearts. We identified 10 EC subclusters. The multidimensionally differential genes (DEGs) analysis across different EC clusters shows molecular changes with aging, showing the increase in the overall inflammatory microenvironment and the decrease in angiogenesis and cytoskeletal support capacity of aged ECs. And we performed an in-depth analysis of 3 special ECs, Immunology, Proliferating and Angiogenic. The Immunology EC seems highly associated with some immune regulatory functions, which decline with aging at different degrees. Analysis of two types of neovascular ECs, Proliferating, Angiogenic, implied that Angiogenic ECs can differentiate into multiple EC directions after initially originating from proliferating ECs. And aging leads to a decrease in the ability of vascular angiogenesis and differentiation. Finally, we summarized the effects of aging on cell signaling communication between different EC clusters. This cardiac EC atlas offers comprehensive insights into the molecular regulations of cardiovascular aging, and provides new directions for the prevention and treatment of age-related cardiovascular disease.

Immunomodulation by endothelial cells - partnering up with the immune system?

Blood vessel endothelial cells (ECs) have long been known to modulate inflammation by regulating immune cell trafficking, activation status and function. However, whether the heterogeneous EC populations in various tissues and organs differ in their immunomodulatory capacity has received insufficient attention, certainly with regard to considering them for alternative immunotherapy. Recent single-cell studies have identified specific EC subtypes that express gene signatures indicative of phagocytosis or scavenging, antigen presentation and immune cell recruitment. Here we discuss emerging evidence suggesting a tissue-specific and vessel type-specific immunomodulatory role for distinct subtypes of ECs, here collectively referred to as 'immunomodulatory ECs' (IMECs). We propose that IMECs have more important functions in immunity than previously recognized, and suggest that these might be considered as targets for new immunotherapeutic approaches.

Clinical relevance of circulating antibodies and B lymphocyte markers in allograft rejection

The main challenge in solid organ transplantation remains to tackle antibody-mediated rejection. Our understanding of the antibody-mediated response and the capacity to detect it has improved in the last decade. However, the sensitivity and specificity of the current clinical tools to monitor B cell activation are perfectible. New strategies, including the refinement in the characterization of HLA and non-HLA antibodies, as well as a better understanding of the circulating B cell phenotype will hopefully help to non-invasively identify patients at risk or undergoing antibody-mediated allograft damage. The current review discusses the current knowledge of the B cell biomarkers in solid organ transplantation, with a focus on circulating antibodies and peripheral B cells.

Relationship of HLA‐DR Expression to Rejection and Mononuclear Cell Infiltration in Renal Allograft Biopsies

Research on renal biopsies has shown that HLA class I antigens are distributed throughout the renal parenchyma, but that the distribution of HLA-DR varies greatly. We investigated HLA-DR expression in biopsies of 90 renal transplants, and also semiquantitatively assessed the proportions of CD68-, CD3-, and HLA-DR-positive infiltrating cells by immunohistochemistry. The relationships between tubular DR expression and interstitial lymphocyte and macrophage infiltration were examined. Forty of the biopsies showed acute rejection (AR), 33 showed chronic rejection (CR), 10 showed suspected rejection (SR), and 7 showed no evidence of rejection (NR). HLA-DR expression was noted in 35/40 (87.5%) of the AR cases, 22/33 (66.6%) of the CR cases, and 6/10 (60%) of the SR cases. Only 1 (14.3%) of the NR cases exhibited HLA-DR antigen expression in the renal tubules. The proportions of lymphocyte and macrophage infiltration observed in the interstitium were significantly correlated with tubular DR expression in all cases (p<0.01). At 6 months after biopsy was done, 24/35 (68.6%) of the AR patients with tubular DR expression had showed second episode of rejection or showed deteriorated renal function. The remaining 11 AR cases with tubular DR expression had stable renal function at this stage. The cases that had no significant tubular DR expression had no problems with rejection or functional deterioration. These findings are consistent with the theory that expression of HLA-DR antigens on renal tubular cells may be a marker of rejection and poor graft outcome.

Unusual expression of human lymphocyte antigen class II in normal renal microvascular endothelium

BACKGROUND

The human lymphocyte antigen (HLA) class II proteins (DR, DQ, and DP) and DM, a protein involved in loading antigenic peptide onto the class II molecules, have a coordinate regulation that facilitates antigen presentation to CD4+ T cells. CIITA is a specific transcription factor responsible for the coordinate regulation of these genes. DR expression in the kidney was described to be constitutive on renal microvascular endothelium in the early 1980s, but expression of other genes involved in class II antigen presentation (DQ, DP, DM, and CIITA) has not been characterized.

METHODS

Expression of the HLA class II proteins, DM, and CIITA in normal human kidney cortex was evaluated by immunofluorescence microscopy, Northern blots, and reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

The endothelium of glomerular and peritubular capillaries constitutively express DR, as indicated by colocalization of DR and CD31 antibodies. However, the endothelium of larger renal blood vessels is devoid of class II proteins. Capillaries that express DR do not have detectable DQ, DP, or DM by immunofluorescence. Northern blots identified DR, DP, and DM mRNAs but not DQ mRNA. CIITA was amplified by RT-PCR at a level that could account for the class II expressed by the microvascular endothelium.

CONCLUSION

The renal microvascular endothelium constitutively expresses DR without the other class II proteins or DM. This discoordinate expression of HLA class II genes is unusual and may contribute to the kidney's ability to control CD4+ T-cell responses.

Dendritic cells in glomerulonephritis

Renal biopsies (n = 45) from patients with various forms of glomerulonephritis (GN), comprising mesangial IgA-GN (n = 25), focal glomerular sclerosis (n = 13) and acute GN (n = 7), were examined by double staining immunocytochemistry (APAAP, streptavidin-peroxidase) using unconjugated monoclonal antibodies (Ab) against--(i) the CD1b antigen expressed on dendritic cells (DCs), (ii) the invariant chain (Ii), and (iii) biotin-conjugated Ab against HLA-DR. In normal control kidneys (n = 7) without interstitial inflammation, CD1b-positive DCs were not detected. Glomerular endothelial cells and a few cells in mesangial areas showed double staining with the Ab against HLA-DR in Ii. In GN without active interstitial inflammation (n = 9), CD1b-positive DCs were not found. In biopsies with interstitial inflammation (n = 36) CD1b-positive DCs were found interspersed among other inflammatory cells. In seven of the biopsies showing IgA-GN DCs were seen in the vicinity of those glomeruli that exhibited either crescents or glomerular sclerosis with splitting of Bowman's capsule. In proximal tubular epithelial cells de novo expression of HLA-DR/Ii-chain was only seen when DCs were present. We conclude that in different forms of GN: (i) CD1b-positive DCs play an important role in the development of interstitial inflammation, and (ii) their presence may be related to the de novo coexpression of HLA-DR/Ii in tubular epithelial cells, possibly mediated through the production of interferon gamma and other cytokines.

Etiologic factors in renovascular fibromuscular dysplasia. A case-control study

The role of several factors that have been suggested as being of etiologic importance in renovascular fibromuscular dysplasia was examined in a case-control study of 33 patients with angiographically demonstrated fibromuscular dysplasia and 61 renal transplant donor control subjects with normal renal arteries. The factors studied included use of oral contraceptive agents or markers of sex hormone dysfunction, mechanical stress to the renal artery wall, human lymphocytic antigen (HLA) type, cigarette smoking, history of hypertension for more than 5 years, and family history of cardiovascular disease. The risk of fibromuscular dysplasia was significantly (p = 0.003) increased (odds ratio = 4.1, 95% confidence interval = 1.5-10.9) among cigarette smokers. A significant (p less than 0.001) dose-response relation was noted between cigarette use and the risk of fibromuscular dysplasia developing (odds ratio = 8.6 for those who had smoked more than 10 pack-years). Personal history of hypertension more than 5 years was also associated (odds ratio = 5.0, 95% confidence interval = 1.1-22.8) with a significantly (p = 0.036) increased risk for the development of fibromuscular dysplasia. HLA-DRw6 antigen was more common in the 33 fibromuscular dysplasia patients than in the 61 renal transplant donor control subjects (odds ratio = 3.00, p = 0.067) or a second group of 934 ambulatory control subjects (odds ratio = 2.51, p = 0.031). Adjustment for cigarette smoking increased the odds ratio to 5.0 (95% confidence interval = 1.3-19.6). There was a positive though not statistically significant (odds ratio = 1.7, p = 0.175) association noted between family history of cardiovascular disease and fibromuscular dysplasia.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of HLA-DQ, -DR, and -DP antigens in normal kidney and glomerulonephritis

Expression of the defined subtypes of HLA-class II antigens DQ, DR, DP, as well as of a putatively new HLA-class II determinant DY was evaluated with specific monoclonal antibodies on frozen sections of 15 normal kidneys, as well as of renal tissue of 65 patients with different forms of glomerulonephritis (GN). In normal kidney HLA-DR and/or -DY versus DQ or DP antigens were shown to be differentially expressed on subpopulations of glomerular and interstitial cells, as well as vascular endothelia. Normal proximal tubular epithelia lacked HLA-DQ and -DP antigens, but carried -DY and variably -DR products constitutively. In comparison, aberrant presence of HLA-DQ and/or -DP antigens was found on proximal tubular cells in the majority of patients with rapidly progressive (RPGN), membranoproliferative GN (MPGN), or focal glomerular sclerosis (FGS), but more rarely observed in other forms of proliferative or non-proliferative GN. In addition all cases with RPGN revealed reduction of HLA-DQ, -DR, -DP or -DY+ glomerular cells. Decline of HLA-DP and/or -DR+ glomerular cells was variably seen in mesangioproliferative glomerulonephritis (MesPGN) and MPGN, whereas in FGS HLA-DQ antigens appeared to be increased in glomeruli. HLA-DQ, -DR, -DY+ interstitial cellular infiltrates were present in RPGN, FGS and MPGN and only occasionally occurred in other forms of GN. Altered renal expression of HLA-class II antigens may indicate specific sites of immunologically-mediated kidney injuries in GN.

Immunoregulation in arthritis. A review on synovial immune reactions in RA and in some experimental animal models for arthritis

Local synovial immune reactions have during recent years been characterized both in human arthritides, particularly in rheumatoid arthritis (RA), and in animal models for arthritis. Common characteristics of human RA on one hand and experimental adjuvant arthritis and collagen arthritis on the other hand, are induced expression of class II transplantation antigens on synovial cells close to the cartilage and presence of activated T lymphocytes in close proximity to these class II expressing cells. The present review aims to describe some implications of these and subsequent findings both concerning the analysis of the pathogenesis of RA and concerning some therapeutic implications derived from parallel studies on relevant features of the human RA and the respective animal models for arthritis.

Immunoglobulin M antibodies present in the acute phase of Kawasaki syndrome lyse cultured vascular endothelial cells stimulated by gamma interferon

Kawasaki syndrome (KS) is characterized by diffuse vasculitis and marked T cell and B cell activation. In this study, sera from 16 patients with acute KS, 15 patients in the convalescent phase of KS, and 19 age-matched controls were assessed for complement dependent cytotoxic activity against 111In-labeled human umbilical vein endothelial (HUVE) cells, Neither sera from patients with KS nor sera from controls had cytotoxic effects on HUVE cells cultivated under standard conditions. Since activated T cells such as those present in acute KS secrete gamma interferon (gamma-IFN), we also examined the effects of sera from acute KS on HUVE cells preincubated with gamma-IFN. We report here that immunoglobulin M (IgM) antibodies in sera from patients with acute KS cause significant (P less than 0.01) killing of gamma-IFN-treated HUVE cells. Pretreatment with interleukin 2, gamma-IFN, or beta-IFN failed to render HUVE susceptible to lysis with acute KS sera. The observed effects were not mediated via immune complexes. The cytotoxic antibodies in acute KS seem to be directed against inducible monomorphic antigenic determinants present on gamma-IFN-treated HUVE cells but not on control or gamma-IFN treated autologous human dermal fibroblasts (HDF). Similarly, acute KS sera also induced lysis of gamma-IFN-treated human saphenous vein endothelial (HSVE) cells but not gamma-IFN treated human saphenous vein smooth muscle (HSVSM) cells. Since gamma-IFN induces the same level of class I and class II major histocompatibility complex (MHC) antigen expression on HDF, HUVE, HSVE, and HSVSM cells, our results suggest that the anti-endothelial cell antibodies in acute KS are directed to gamma-IFN-inducible molecules other than MHC determinants. These observations are further substantiated by the failure of human B cells or monocytes to absorb the anti-endothelial cell activity. Since most vasculitides, including acute KS, are characterized both by marked immune activation and the secretion of lymphokines, antibodies directed to gamma-IFN-inducible endothelial cell antigens may represent a general mechanism for vascular injury.

Lymphokine dependence of in vivo expression of MHC class II antigens by endothelium

Changes in the expression of class II antigens of the major histocompatibility complex (MHC) have an integral role in the regulation of immune responses, and are brought about in vitro by soluble mediators. However, the mechanism that underlies in vivo expression of MHC class II antigens in, for example, endothelial cells in the absence of immunological stimulation has not been studied. We demonstrate here that expression of MHC class II antigens is not a constitutive property of endothelial cells, for MHC class II antigen-positive endothelial cells do not express these antigens during treatment with the immunosuppressive agent cyclosporin A. In vivo MHC class II antigen expression by canine endothelial cells is therefore dependent on factors, probably the lymphokine gamma-interferon produced by the immune system, whose secretion is inhibited by cyclosporin A.

Abnormal expression of HLA-DR antigen in the placenta of a patient with pemphigoid gestationis

The villous stroma and fetal endothelium in chorionic villi adjacent to maternal decidua in a placenta of a woman suffering from pemphigoid gestationis were found to have abnormal expression of HLA-DR antigen. This aberrant DR expression may be a reflection of an immune attack on the placenta.

Increased expression of HLA-DR antigens on renal tubular cells in renal transplants: relevance to the rejection response

Whether the expression of DR antigens is altered in cadaver renal transplants was examined by the use of monoclonal antibodies to the non-polymorphic region of the DR molecule and an indirect immunoperoxidase stain. Expression of DR antigens increased considerably on renal tubular cells in all 25 biopsy specimens which showed severe cellular rejection, but in only 4 of 14 biopsy specimens with no or minimum evidence of rejection. 2 of these 4 specimens were from patients recently treated for severe rejection and the other 2 subsequently lost their grafts from chronic rejection. DR antigens were also expressed on the cell surface of isolated tubular cells aspirated from transplanted kidneys with acute cellular rejection but not on tubular cells in normal kidneys or aspirates from kidneys without rejection. Biopsy specimens with increased DR expression in tubules usually had an interstitial T cell infiltrate. Expression of DR antigens on tubular cells was not related to HLA-DR incompatibility between donor and host, or to the type of immunosuppressive therapy given. The expression of DR antigens on renal tubular cells may be induced by the infiltrating activated T cells or be a consequence of tubular regeneration following rejection or ischaemic damage. The increased expression of DR antigens on renal tubular cells during rejection makes these cells potential targets for delayed type hypersensitivity responses, which are only effective against DR antigen bearing cells.

HLA-A, B, C; -DR; -MT, -MB, and SB antigens on unstimulated human endothelial cells

Since major histocompatibility complex (MHC) antigens of class II play an important role in organ transplantation, we attempted to demonstrate their expression on endothelial cells which are abundant in transplants with vascular blood supply. Our analysis was performed with monomorphic and polymorphic monoclonal antibodies employing a microscopic immunofluorescence assay and flow cytometry on unstimulated endothelial cells isolated from umbilical cord veins. No evidence was found for the presence of HLA-DR antigens and determinants associated with MT, MB and SB. MHC class I antigens exhibited reduced expression. These findings were confirmed in respect to alloantigens by the use of conventional cytotoxic tissue typing antisera. MB and SB antigens were present on most cord B lymphocytes, but could only be demonstrated on a subpopulation of monocytes exhibiting a lower antigen density at the cell surface. MT and DR antigens were found on most cord monocytes and B lymphocytes.

Antigenic composition of human renal vascular endothelium assessed by kidney perfusion

Intravascular perfusion of healthy, viable human kidneys either with human sera or with monoclonal antibodies specific for individual HLA-A, B, DR or E-M antigens demonstrated that all of these antigens are exposed to circulating antibodies and thus can serve as stimuli or targets for immunologic mediators of renal transplant rejection. In addition, these antibodies could be recovered from the renal vessels by brief treatment with acid buffer.

Presence of complement-fixing anti-endothelial cell antibodies in systemic lupus erythematosus

Vasculitis in systemic lupus erythematosus (SLE) is associated with the deposition of IgG and complement in blood vessel walls. However, it is not known whether immune injury to endothelial cells is a part of this process. Therefore, we used a solid phase radioimmunoassay to study the ability of IgG from normal human sera and sera from patients with SLE to bind to endothelial cells. In this assay, cultured human umbilical venous endothelial cells were sequentially incubated with normal or SLE sera, goat anti-human IgG, and 125I-labeled staphylococcal protein A (*SPA). After exposure to normal sera, 2.5 +/- 0.5% (mean +/- SD) of the added *SPA bound to the cells, whereas after exposure to SLE sera 13.8 +/- 7.6% of the added *SPA bound to these cells. This difference in binding was highly significant (P less than 0.001). Binding was partially reduced when SLE sera were preincubated with B-lymphocytes or monocytes, but not after exposure to erythrocytes, platelets, or T lymphocytes. Incubation of endothelial cells with the 7S fraction of SLE sera or with the F(ab')2 fragment of SLE-IgG resulted in the deposition of greater than 80% as much IgG as was deposited on endothelial cells by whole serum. However, since higher molecular weight fractions (greater than 7S) of SLE sera were also active, we tested the capacity of endothelial cells to bind IgG complexes. Endothelial cells bound heat-aggregated IgG (HA-IgG) in a saturable manner at one log concentration below the binding of normal monomeric IgG. Binding of HA-IgG to endothelial cells was markedly enhanced by preincubation with a serum source of complement. Both HA-IgG and SLE-IgG also bound to freshly obtained endothelial cells in suspension, as detected by automated fluorescence flow cytometry. Binding of SLE-IgG and HA-IgG to endothelium initiated complement activation, deposition of the third component of complement, and disruption of the monolayer. In addition, SLE-IgG and HA-IgG caused endothelial cells to secrete prostacyclin and caused the adherence of platelets, confirmed by scanning electron microscopy. These studies demonstrate that IgG anti-endothelial antibodies are present in the sera of patients with active SLE. These sera may also contain IgG complexes that are capable of binding to endothelial cells. The association of IgG and complement with endothelial cells may initiate vascular injury in SLE and other human disorders.

Cultured human and rat oligodendrocytes and rat Schwann cells do not have immune response gene associated antigen (Ia) on their surface

In order to determine if oligodendrocytes or Schwann cells had surface immune response gene associated antigen (Ia), we studied the binding of: (a) mouse monoclonal antibodies to rat Ia, to cultures of rat oligodendrocytes and Schwann cells; and, (b) mouse monoclonal antibodies to human Ia, to cultures of human oligodendrocytes employing radioimmunoassay and indirect immunofluorescence. Cells were identified using phenotypic markers; rabbit anti-galactocerebroside (GalC) for oligodendrocytes; rabbit anti-GalC and rabbit anti-Schwann cell for Schwann cells; rabbit anti-glial fibrillary acidic protein for astrocytes; rabbit anti-fibronectin for fibro-blasts and leptomeningeal cells, and the capacity to ingest latex particles for macrophage-microglia. Ia could not be detected on the surface of oligodendrocytes, Schwann cells, astrocytes, fibroblasts, or leptomeningeal cells. A small number of latex ingesting cells bound anti-Ia even after blocking of surface Fc receptors.

Transfer of anti-HLA-DR antibodies from the mother to the child. Are DR antigens expressed on the placenta?

Materno-foetal transfer of anti-HLA-DR antibodies was studied in 7 women. In 6 cases, the antibody was induced by the current pregnancy and in one case, it was a residual antibody from a previous pregnancy. When the maternal antibody was induced by the current pregnancy, no anti-DR antibody was detected in the child. When the antibody was residual, it was weakly present in the child. A comparison was made between the materno-foetal transfer of anti-HLA-A,B,C antibodies and that of anti-DR antibodies. Anti-HLA-DR antibody placental absorption suggested that the corresponding antigens were expressed on certain placenta cells.

Ia antigens in rat kidney, with special reference to their expression in tubular epithelium

The distribution of Ia antigens in rat kidneys has been investigated by an immunoperoxidase technique, using monoclonal antibodies directed at framework determinants on molecules equivalent to gene products of the I-A and I-E/C regions of the mouse major histocompatibility complex (MHC). Antigens mapping to both loci were detected in proximal convoluted tubule epithelium and on scattered dendritic cells in the interstitial connective tissues, glomeruli, and mucosa of the renal pelvis. All other structures were negative. Genetic studies indicate that the levels of expression of Ia molecules from both genetic loci are controlled by non-MHC genes in epithelium, but not on lymphocytes. The subcellular distribution of Ia molecules has been investigated in tubular epithelium and is discussed in relation to their possible functions in epithelia.

Anti-Ia-reactive cells in the urinary tract of man, guinea-pig, rat and mouse

Tissues from the urinary tract of man, the guinea-pig, mouse and rat were investigated for Ia (HLA-DR) tissue distribution with an immunohistochemical staining technique using anti-Ia monoclonal antibodies. Human and guinea-pig tissues were also investigated with a rabbit anti-human HLA-DR immunoglobulin. Ia-antigen-expressing cells were demonstrated in bladder connective tissue of man, the guinea-pig, rat and mouse. In man and the guinea-pig anti-Ia-reactive cells were present also in the bladder epithelium. In the kidney, the Ia antigens seemed to be restricted to the endothelium in man, the guinea-pig and mouse, whereas in the rat, the kidney contained anti-Ia-reactive dendritic cells in the interstitium. The staining of mouse tissues with anti-I-Ak- and anti-I-E/Ck-specific monoclonal antibodies revealed that cells of different Ia phenotypes were differently distributed in the bladder connective tissue. In sections from the mouse kidney no difference in staining was seen with the various antibodies. In experiments with mouse bone-marrow chimeras the anti-Ia-reactive cells in mouse bladder were shown to be of bone-marrow origin. In humans epithelial Ia-expressing cells could be isolated from the urine. Such cells might constitute a source of anti-Ia-reactive epithelial cells for future functional studies.