Variable expression of major histocompatibility antigens: role in transplantation immunology

Donor-specific sensitization by cadaveric venous allografts used for arterial reconstruction in peripheral arterial occlusive vascular disease

The use of allogeneic venous grafts from postmortal organ donors allows for the reconstruction of critically affected arteries in patients with peripheral occlusive vascular disease. We were interested to determine the prevalence and specificity of anti-HLA antibodies in patients after allogeneic vein transplantation. Anti-HLA class I and II alloantibodies were analyzed by flowcytometric analysis using color-coded microbeads coated with HLA antigens including recombinant single antigens. Nine out of 10 patients involving 12 venous allografts were positive for anti-HLA alloantibodies. All antibody-positive patients carried both anti-HLA class I and II alloantibodies. Anti-donor HLA specificity of the anti-HLA alloantibodies was seen in seven out of nine patients for anti-class I antibodies and in eight out of nine patients for anti-HLA class II antibodies. A high rate of donor-specific allosensitization was seen after allogeneic venous transplantation. In conclusion, allosensitization not only includes a humoral response against the constitutively expressed class I antigens but also extends to class II antigens.

Increased glomerular and interstitial LFA-1 expression in proteinuric immunoglobulin A nephropathy

The cell populations infiltrating the kidneys and the LFA-1 expression were studied in renal biopsy specimens from patients with proteinuric (n = 15, group 1) and non-proteinuric (n = 12, group 2) immunoglobulin A nephropathy. Both groups were matched for age and renal function at the time of biopsy. Proliferative glomerular changes were more commonly see in group 1. Both groups had similar numbers of intraglomerular and interstitial total leukocytes, monocytes/macrophages, and T cells (P = NS). However, glomerular LFA-1 alpha- and -beta-positive cells were significantly higher in group 1 (2.3 +/- 0.2 and 3.3 +/- 0.1 per glomerulus) than in group 2 (0.2 +/- 0.08 and 0.5 +/- 0.05 per glomerulus) (P < 0.005 and P < 0.01, respectively). Group 1 had much higher interstitial LFA-1 alpha- (109 +/- 20/mm(2)) and -beta-positive cells (157 +/- 40/mm(2)) in comparison with group 2 (29 +/- 12/mm(2) and 42 +/- 17/mm(2)). (P < 0.005 and P < 0.01, respectively). No association between glomerular and interstitial LFA-1-positive cells was seen. In addition, tubular HLA-DR expression was higher in group 1 (29 +/- 6/mm(2)) than in group 2 (9 +/- 2/mm(2)) (P < 0.005), but the interstitial HLA-DR-positive cells were similar in both groups. There was a significant association between interstitial LFA-1 alpha- and -beta-positive cells and tubular HLA-DR expression in group 1 (P < 0.01 and P < 0.005, respectively) but not in group 2. Interestingly, the extent of interstitial but not glomerular LFA-1-alpha and -beta expression was highly related to the degree of proteinuria in group 1 (P < 0.01 and P < 0.002, respectively). In conclusion, proteinuria in immunoglobulin A nephropathy is associated with increased LFA-1 expression by glomerular and interstitial infiltrating cells. However, interstitial but not glomerular LFA-1-positive cells are strongly related with the degree of urinary protein excretion. The exact link between LFA-1 expression and proteinuria needs further investigation.

Scintigraphic detection of early cardiac rejection by iodine 123-labeled monoclonal antibody directed against monomorphic determinant of major histocompatibility complex class II antigens

Although it has been shown that early cardiac rejection can be visualized by radioimmunoscintigraphy targeting major histocompatibility complex class II antigen, the use of antibodies that bind to a polymorphic determinant of class II antigen has certain disadvantages for clinical application. This investigation was designed to examine the feasibility of scintigraphic detection of cardiac allograft rejection by using a monoclonal antibody that reacts with a monomorphic determinant of rat IA antigens. Twenty PVG rats (RT1c) and five DA rats (RT1a) underwent heterotopic transplantation with DA hearts. Two of the 20 allografted rats were treated with FK506 (2 mg/kg/day). Seventeen rats were injected intravenously with 80 microCi of iodine 123-labeled monoclonal antibody reactive with a monomorphic determinant of rat major histocompatibility complex class II antigens (Ox6) 16 hours before scintigraphy, and images were compared with those obtained by injection of 123I-labeled monoclonal antibody against a polymorphic determinant of class II antigens (F17-23-6, anti-RT1a) (n = 8). Background activity was higher in rats injected with Ox6 than in rats injected with F17-23-6. Uptake of labeled Ox6 in the grafts reflected the severity of rejection as determined by histopathologic criteria. Rejecting allografts with lymphocyte infiltration but without myocyte necrosis could be identified by the scintigraphy with use of labeled Ox6.(ABSTRACT TRUNCATED AT 250 WORDS)

Scintigraphic imaging of MHC class II antigen induction in mouse kidney allografts: a new approach to noninvasive detection of early rejection

Mice with kidney transplants were investigated to determine whether early kidney allograft rejection could be detected by radioimmune scintigraphy targeting major histocompatibility complex (MHC) class II antigens induced on donor organ cells. Allografts from C3H/He (H2k) donors were transplanted into BALB/c (H2d) recipients. Each mouse was injected intravenously with 100 microCi of 123I-labeled anti-MHC class II monoclonal antibody (mAb; Y17, anti-IEk) 16 h before scintigraphy. After imaging, mice were sacrificed for tissue counting and histopathological examination. Radiotracer uptake in the nontreated allografts increased starting on the 3rd day after transplantation, peaked at around the 6th day, and then gradually decreased. Rejecting allografts with only focal perivascular mononuclear cell infiltration could be identified by scintigraphy. However, allografted mice without evidence of rejection and isografted mice did not show an increase in radiotracer uptake. Rejecting BALB/c kidney transplanted into C3H/He mice did not show an increase in Y17 mAb uptake, suggesting that class II antigens induced on donor kidneys are solely responsible for the mAb uptake in positive scintigrams of rejecting allografts. Five allografted mice were treated with anti-CD3 mAb and cyclosporin starting 3-9 days after transplantation. Radiotracer uptake decreased after 4 weeks of treatment and increased 2 weeks after the cessation of immunosuppressive treatment, reflecting suppression and recurrence of rejection, as determined by histological examination. These changes could be followed scintigraphically. We conclude that changes in class II antigen expression can be assessed by the 123I-labeled anti-MHC class II antigen mAb and that it is a sensitive and noninvasive method for detecting kidney allograft rejection.

Capillary deposition of C4d complement fragment and early renal graft loss

Clinical outcome of kidney grafts that are affected by the complex syndrome of 'early graft dysfunction' is uncertain and rather unpredictable. In this study, an individual prognosis for dysfunctioning allografts (N = 93) is attempted by the immunohistological assessment of vascular classical complement activation in graft biopsies. Thus, capillary deposition of complement fragment C4d was observed in the majority (N = 51) of early dysfunctioning grafts. In 43 biopsies, abundant deposition of fragment C4d was present in all capillaries, whereas in eight specimens a segmental distribution of capillary C4d was observed. In 42 grafts with early dysfunction no capillary C4d was detectable. Eighteen subsequent graft losses within one year (16 early losses) were recorded in the subgroup with C4d in all capillaries, and three early losses in the group with segmentally distributed C4d. Only four graft losses (3 early losses) were recorded in the C4d-negative group (P = 0.0027; Pearson's chi square test). The resulting one-year graft survival rates (72% for the study group) differed markedly between the subgroups. Grafts with generalized or segmental capillary deposition of C4d had 57% and 63% survival, respectively, contrasted by 90% survival in the C4d-negative group. It is of note, however, that also three of the four grafts that were finally lost within the C4d-negative group, showed distinct capillary deposition of C4d in second biopsies. Vascular deposition of complement fragment C4d therefore represents a clinically relevant factor that contributes to early graft dysfunction. Its assessment is helpful for an individual graft prognosis.

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.

Tubular and interstitial factors in the progression of glomerulonephritis

All recent studies of the outcome of different forms of progressive glomerulonephritis concur that a major factor, apparently determining outcome, is the presence and severity of tubulointerstitial changes, and not the degree of glomerular alteration. Moreover, at the time of biopsy, tubulointerstitial changes correlate much better with the glomerular filtration rate. These at first surprising findings are not only useful clinically, but should make us think about our models of how progression takes place in so-called glomerular nephritides. In fact, a major tubulointerstitial infiltrate of immune-competent cells is present in all forms of progressive glomerulonephritis, and again correlates with outcome. In addition, it is now clear the tubular epithelium is capable of synthesising and secreting a number of factors important in fibrogenesis, and of displaying major histocompatibility complex class II antigens and leucocyte-adhesion molecules. Tubular cells could thus present peptides to T helper cells and amplify, or maybe even initiate, immune reactions. Finally, fibrogenesis within the kidney is at last being studied, long after studies have been performed on liver and lung. In the past, too much attention has been paid to reversible inflammation and not enough to irreversible cirrhosis of the kidney.

Imaging the rejecting heart. In vivo detection of major histocompatibility complex class II antigen induction

BACKGROUND

Mice with abdominal heterotopic heart transplants were studied to determine whether scintigraphic detection of an increase in major histocompatibility complex (MHC) class II antigen expression could be used as a noninvasive method for diagnosing early rejection.

METHODS AND RESULTS

Allografts from C3H/He (H2k) donors were transplanted into BALB/c (H2d) recipients (n = 18). Two of the 18 allografted mice were treated with cyclosporine (15 mg/kg/day), and two isografted mice served as controls. Each mouse was injected intravenously with 100 microCi of 111In-labeled anti-MHC class II monoclonal antibodies (10-2-16 and 14-4-4S) 24 hours before scintigraphy. After imaging, the mice were killed for tissue counting and histopathology. Radiotracer uptake in the grafts reflected the severity of rejection as determined by histopathological criteria. The percent injected dose per gram of tissue in excised grafts was 4.8 +/- 1.8 (mean +/- SD) for normal grafts (n = 8), 11.1 +/- 9.7 for grafts with grade IA rejection (n = 3, NS), 18.0 +/- 3.8 for grafts with grade IIIA rejection (n = 4, p less than 0.001 versus normal), 18.7 +/- 3.2 for grafts with grade IIIB rejection (n = 3, p less than 0.001 versus normal), and 22.6 +/- 5.4 for grafts with severe rejection (grade IV) (n = 3, p less than 0.001 versus normal). Rejecting allografts with lymphocyte infiltration but without significant myocyte necrosis could be identified by this scintigraphic method. In the BALB/c donor-C57BL/6 (H2b, IE-) recipient combination, rejecting allografts were visualized by 14-4-4S (anti-IEk,d,p,r) antibody but not by 10-2-16 (anti-IAk,r,s,f) antibody. This difference shows that class II antigens induced on donor hearts are solely responsible for the antibody uptake in positive scintigrams of rejecting allografts.

CONCLUSIONS

We conclude that 111In-labeled anti-MHC class II antigen antibody imaging is a sensitive and noninvasive method for detecting cardiac allograft rejection.

Application of flow cytometry in clinical renal transplantation

Flow cytometry (FC) may be considered as a fundamental technique in studying cell biology and pathology. It combines the quantitative character of biochemical methods with the multiparametric capacities of microscope analysis in a high-precision process for rapid analysis of individual cell characteristics. Three original FC techniques routinely applied in the field of renal transplantation are reported in the present study. They concern the donor-recipient cross-match test, the morphological analysis of urinary sediment and the modulation of the density of various membrane antigens on the lymphocyte surface. A common factor underlies all these methods: they aim to provide the physician with a reliable diagnostic tool in clinical renal transplantation.

Experimental ablation nephropathy. Fine structure, morphometry, cell membrane epitopes, glomerular polyanion and effect of subsequent transplantation

The subtotal (5/6) nephrectomy performed in 23 adult female rats induced severe hypertrophy of residual parenchyma with interstitial fibrosis, tubular dilatation, and focal and segmental glomerulosclerosis (FSG). This ablation nephropathy (AbN) caused proteinuria, progressive renal failure, and hypertension. The extent of FSG was assessed by semiquantitative scoring. The ultrastructure revealed widespread foot process fusion, many dense cytoplasmic inclusions in podocytes, and degenerative changes or disruption of mesangium with glomerular "microcysts". Numerous granular deposits of rat Ig were seen in the glomeruli but a short praeterminal i.v. load by heat-aggregated human Ig did not alter the morphology of AbN and produced discrete and inconstant glomerular deposits. Similarly an i.v. injection of protamine and heparin generated protamine-heparin complexes seen in various layers of glomerular capillary wall, similar to those found previously in normal rats. AbN displayed a partial irregular depletion of polyanion sites reactive with polyethylenimine in lamina rara externa. A significant increase in both glomerular and interstitial Ia+ cells and a marked predominance of W3/25+ cells in the interstitial infiltrates were documented by immunohistochemistry in the remnant kidneys. Both AbN and FSG could be largely corrected (or prevented?) by subsequent syngeneic renal transplantation (TPL; 6 animals). On the other hand a severe AbN was found in two post-ablation residues after unsuccessful TPL with graft necrosis or sclerosis.--AbN has some analogies to various chronic human nephropathies (e.g. FSG) and may explain their progression to the terminal failure. Degenerative and finally destructive mesangial lesion seems to be of prime importance in AbN.

Mechanism, pathophysiology, diagnosis, and management of renal transplant rejection

In recent years, there has been a steady progress in basic research (immunogenetics and cellular immunology) that helped us in understanding the mechanisms underlying allograft rejection. Several laboratory tests were developed, and the results were shown to correlate with clinical rejection. However, most of these studies have not found a place in clinical practice because of their nonspecificity, lack of sensitivity, time lag, added expense, and inconvenience. The commonly employed diagnostic tests (i.e., renal transplant ultrasound and 131I hippuran scintigram) are helpful in differentiating rejection from other causes of graft malfunction. The specific renal parenchymal disease, such as acute or chronic rejection or de novo or recurrent glomerular disease, contributing to graft malfunction can only be diagnosed by renal histopathologic study. Because hyperacute and accelerated acute rejections are irreversible and necessitate graft nephrectomy, measures should be taken to prevent this problem. High-dose corticosteroids still remain the mainstay of therapy for acute cellular rejection. In the case of steroid-resistant rejections, treatment with ALG or OKT3 appears promising. As there is no effective therapy for chronic allograft rejection, usual measures of delaying the progression of chronic renal failure should be employed, and patients should be advised to return to maintenance dialysis before they develop uremic symptoms. If current experiments demonstrating selective immunosuppression with monoclonal antibodies are found successful in human trials, one can expect further improvement in the outcome of renal transplantation.

The role of adaptation in allograft acceptance

The experimental and clinical data suggest that both a decrease of antigen expression and decreased perfusion can protect against immunologically mediated destructive processes. In the adaptation of skin grafts, these factors could be interrelated. Inadequate perfusion might lead to a decreased delivery of substances that stimulate MHC antigen expression. This course of events also could explain the protection in the patient presented here. Immune deposits were completely absent in the protected segment of the kidney, although immune deposits were abundantly present in the remaining part of the kidney, and circulating anti-donor antibodies were demonstrable after the transplanted kidney had been removed. The limited availability of frozen biopsy material has prevented us from comparing the expression of MHC antigens in both kidney segments using monoclonal antibodies. But such studies might be done in experimental kidney transplants with an artificially induced stenosis of the renal artery. Except when an arterial stenosis is present, we have little reason to assume that perfusion gradually decreases in longstanding kidney grafts as it does in skin grafts. Therefore, if adaptation plays a role in the gradual decrease of the sensitivity to rejection in longstanding kidney grafts, this phenomenon must be attributed to a decreased expression of target antigens as a consequence of factors other than decreased perfusion. The most likely candidates are the immunosuppressive drugs, such as cyclosporine and prednisone, which decrease MHC antigen expression. Let me conclude by returning to my main theme of graft adaptation. It seems appropriate to end this review with a quotation from one of Woodruff's original publications on this subject: "If the phenomenon [adaptation] applies to homotransplants of normal tissues to sites other than the eye, I think it almost certain that the clinical homograft problem will be solved; if it does not, the problem may prove insoluble" [9]. Although our insight into the rejection process has increased considerably, we still do not know which factors are most important in determining the long-term survival of primarily vascularized grafts.

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.

Interferon beta 1, an intermediate in the tumor necrosis factor alpha-induced increased MHC class I expression and an autocrine regulator of the constitutive MHC class I expression

In conclusion, our observations indicate that the constitutive MHC class I expression is regulated by autocrine production of IFN-beta 1. TNF-alpha acts as an enhancer of the autocrine production of IFN-beta 1, and consequently as an enhancer of the MHC class I expression and viral protection.