IL-6 independent monocyte/B cell defect in renal transplant recipients with long-term stable graft function

We showed previously that the B cell response in renal transplant recipients with long-term stable graft function (ST patients) is significantly affected by T suppressor activity. To further assess the role of the monocyte/B cell compartment in B cell regulation, we tested B cell responses in 30 ST patients (> 1 year after transplant) and 15 patients with chronic rejection (CR patients). PWM was used for T cell-dependent B cell stimulation in an allogeneic coculture system, and SAC I for T cell- and monocyte-independent B cell stimulation. B cell responses were assessed in a reverse hemolytic plaque assay and by ELISA determination of IgM, IgG, and IL-6 in culture supernatants. In PWM-stimulated cultures of ST patients, we found a diminished immunoglobulin-secreting cell (ISC) formation (P < 0.0001 and P < 0.05, compared with controls and CR patients, respectively) and diminished IgM secretion (P = 0.06 and P < 0.01, respectively), whereas CR patients and controls were not significantly different. Two of 35 (6%) controls and 3 of 15 (20%) CR patients, in contrast to 20 of 30 (67%) ST patients, displayed defective ISC formation (P < 0.0001). This defective B cell response may be the result of reduced CD36+ monocyte counts in ST patients (P < 0.005), as PWM-stimulated B cell responses and CD36+ cell counts were significantly associated (P < 0.05, ISC and IgM response). A role of monocytes in the impairment of B cell function is further supported by decreased plasma neopterin levels in ST compared with CR patients (P = 0.0001), a significant association between plasma neopterin and PWM-stimulated B cell responses (P < 0.05, ISC response; P = 0.0001, IgM response), and by the finding that B cell responses in ST patients after monocyte-independent stimulation with SAC I were unaffected. ST and CR patients showed no significant differences in B cell subsets, plasma IL-6, or IL-6 responses of mitogen-stimulated cultures. Our data indicate that an IL-6-independent monocyte or B cell defect plays a role in the maintenance of stable transplant function.

Einfluß der HLA-Kompatibilität auf die Nierentransplantation

Der Einfluß des HLA-Systems auf die Erfolgsrate von Nierentransplantationen wurde in einer weltweiten Studie ausgewertet. Der Einfluß der HLA-Chromosomen auf Transplantationen von Verwandtenspendern wurde bestätigt. Bei Transplanta-tionen von Leichenspendern wurde ein hochsignifikanter Effekt der Kompatibilität zwischen Spender und Empfänger für die HLA-A-, -B- und -DR-Antigene festge-stellt (p < 0,0001). Die große Bedeutung einer guten Typisierungs<i>qualität</i> wurde verdeutlicht durch a) einen signifikanten Einfluß der HLA-A-, -B-Antigene, wenn die Typisierung auf «Split»-Untergruppen durchgeführt wurde, nicht jedoch wenn lediglich «breite» Antigene typisiert wurden, und b) einen verbesserten Effekt der HLA-DR-Kompatibilität, wenn serologische Typisierungsfehler mittels einer molekularbiologischen Typisierung korrigiert wurden. Durch eine Nierenzuteilung nach der HLA-Kompatibilität ist ein Gewinn von 800 Nierenfunktionsjahren je 1000 Transplantationen über einen 10-Jahres-Zeitraum erreichbar.

Incidence of non-Hodgkin lymphoma in kidney and heart transplant recipients

Organ transplant recipients receive immunosuppressive drugs to prevent graft rejection. This treatment has been associated with higher rates of non-Hodgkin lymphoma (NHL) than in the general population. We assessed the incidence of NHL in a multicentre study of 45,141 kidney transplant patients and 7634 heart transplant recipients. The NHL rate was especially high during the first post-transplant year among both kidney transplant recipients (101 cases vs 2.7 expected in general population; 224 per 10(5)) and heart transplant recipients (93 vs 0.6 expected; 1218 per 10(5)). The incidence was lower in subsequent years (43 and 371 per 10(5) in kidney and heart transplant recipients). During the first year the NHL incidence was higher in North America than in Europe (relative risk 2.12 [95% CI 1.55-2.89]). There were also significant increases in risk for patients who received rejection prophylaxis with antilymphocyte antibodies (1.80 [1.31-2.46]) and in those who received both cyclosporin and azathioprine rather than another immunosuppressive combination (1.47 [1.03-2.08]). This study quantified the risk of NHL after kidney or heart transplantation. It suggests that the risk of NHL is related to the aggressiveness of the immunosuppressive regimen.

A proposal for improved cadaver kidney allocation

The allocation of cadaver kidneys for transplantation should have two objectives: a fair distribution of kidneys among the waiting recipients and a high success rate. Currently, organ exchange organizations are following mainly a policy of success oriented allocation in that the kidneys are distributed according to the best achievable HLA match. A consequence of this policy is that patients with rare HLA phenotypes experience prolonged waiting times and that there are large kidney exchange imbalances among transplant centers. Based on theoretical considerations, we described previously the selection routine COMB which was aimed at decreasing excessive waiting times. In this study we present an extension of this routine called XCOMB which builds on realistic conditions according to the current Euro-transplant waiting list. This new procedure decreases the average and maximum waiting time, adjusts for rare HLA phenotypes and HLA homozygosity, provides for a reasonably balanced kidney exchange rate among centers, and guarantees an HLA match distribution and overall transplant success rate near the theoretically possible optimum. The program was tested in an extensive simulation based on actual data derived from 35,000 cadaver kidney transplants. Although more complex than procedures currently in use, the program's efficient software allows the selection of a patient within one second from a waiting list of 10,000 potential recipients, using readily available computer hardware.

Complementarities and network interactions in AIDS

The contribution of autoimmune phenomena to the development of AIDS is not fully understood. In this paper we provide new evidence that idiotypic network interactions are operative in the development of AIDS. We furthermore present a model that involves two groups of antibodies and other molecules that are related to each other by a network of specific complementarities. We define Group I molecules to include antibodies and other molecules that have direct or indirect similarities with class I MHC molecules, and Group II substances that have similarities with class II MHC. We observe an inverse relationship between Group I antibodies (including anti-Fab) and Group II antibodies (including anti-anti-gp120, anti-anti-CD8 and anti-rCD4). The potential roles of members of these two groups in AIDS pathogenesis and/or protection are discussed.

A new method for determining anti-B cell antibodies and their specificity using flow cytometry

We describe a new flow cytometric B cell crossmatch method with improved sensitivity and specificity. It is based on the coating of B cell surface immunoglobulins with an unconjugated polyvalent anti-human immunoglobulin antibody. The method also provides a means for determining the specificity of anti-B cell antibodies and, potentially, for anti-HLA class II antibody specificity differentiation (DR, DQ or DP) in a binding inhibition test using mouse monoclonal antibodies directed against human HLA class II antigens.

Association of T cell and macrophage dysfunction with surface gp 120-immunoglobulin-complement complexes in HIV-infected patients

The mechanism of CD4+ cell depletion and functional T helper cell inhibition in HIV-infected individuals is poorly understood. The present study demonstrates that immune complex-covered CD4+ cells are associated with T cell inhibition and macrophage stimulation. We studied 30 patients with ARC/AIDS and 35 asymptomatic HIV+ haemophilia patients. Overall, 20 +/- 3% of peripheral CD4+ lymphocytes were covered with gp120 (range 0-94%). gp120+ cells also exhibited surface-bound IgG (P = 0.0001), IgM (P = 0.0001), and complement (P = 0.0001). Decreased in vitro lymphocyte proliferation was associated with the immune complex load of CD4+ cells. The higher the percentage of CD4+ gp 120+ cells in the blood, the lower the T cell response in vitro (P = 0.001). Moreover, an association was found between immune complex-positive cells and plasma neopterin (P = 0.01). Patients with increased plasma neopterin levels had decreased in vitro responses to pokeweed mitogen (PWM) (P = 0.006), phytohaemagglutinin (PHA) (P = 0.004), concanavalin A (Con A) (P = 0.09), and anti-CD3 MoAb (P = 0.03), and decreased CD4+ cell counts in the blood (P = 0.006). Since maximally 1% of CD4+ lymphocytes are infected with HIV, T cell dysfunction and T cell depletion in HIV-infected patients may also be caused by the release of free gp120 that binds to uninfected CD4+ cells. Our data suggest that the functional inhibition and subsequent elimination of uninfected CD4+ lymphocytes with surface gp120-immunoglobulin-complement complexes may be a pathomechanism in the manifestation of AIDS.

Suppression of anti-erythrocyte autoantibody-producing B cells by a physiological IgG-anti-F(ab')2 antibody and escape from suppression by tumour transformation; a model relevant for the pathogenesis of autoimmune haemolytic anaemia

We showed previously that broadly reactive IgG anti-immunoglobulin autoantibodies produced by rats during the immune response suppress the B cell response. We report here on the effect of a similar human antibody on self-reactive human B cells. IgG anti-F(ab')2 was added to cultures of anti-erythrocyte autoantibody-producing B cells derived from healthy donors. A dose-dependent suppression of the antibody response was obtained (maximum at 1.3 ng IgG/10(6) cells). This effect was competitively inhibited by F(ab')2 gamma. Autoimmune haemolytic anaemia can be caused by chronic monoclonal B cell proliferation. To reproduce this condition in vitro we immortalized B cells with Epstein-Barr virus (EBV) and raised a B cell population with anti-erythrocyte autoantibody activity. These cells were electrically fused with CB-F7 tumour cells and an IgG1 cold-reactive anti-erythrocyte autoantibody-producing B cell line was established. Surprisingly, the tumour cells were not suppressed by IgG anti-F(ab')2. It is known that anti-immunoglobulins selectively suppress antigen-receptor (AgR)-occupied B cells by a Fc gamma-receptor (Fc gamma R)-mediated mechanism. To occupy their AgR, we preincubated the tumour cells with anti-AgR antibody. In spite of this, their susceptibility to suppression was not restored. As shown by rabbit IgG-sensitized ox erythrocyte (EA)-rosetting, this refractoriness was not due to a loss of Fc gamma R. Our experiments delineate a mechanism of peripheral B cell suppression to autoantigens, and show a way of escape from control relevant for the pathogenesis of autoimmune haemolytic anaemia.

Molecular mimicry between HIV-1 and antigen receptor molecules: a clue to the pathogenesis of AIDS

There is increasing evidence that autoimmune phenomena play an important role in the immunopathogenesis of AIDS. We found a high degree of sequence homology between HIV-1 and antigen receptor molecules, immunoglobulins and T cell receptors. Based on recent findings that the appearance of anti-Fab autoantibodies and attachment of gp120/immunoglobulin/complement complexes on CD4+ T cells are associated with the decrease of CD4+ T cells in HIV-infected patients, we hypothesize herein that cross-reactive anti-F (ab')2 autoantibodies and circulating gp120 molecules are responsible for a destabilization of the immune network and the elimination of CD4+ T cells.

IgA-anti-Fab autoantibodies and disease progression in AIDS

There is increasing evidence that autoimmune phenomena contribute to the pathogenesis of the acquired immunodeficiency syndrome (AIDS). We investigated the relationship between IgA autoantibodies directed against the Fab part of the IgG molecule and disease progression in 87 HIV-infected hemophilia patients. AIDS patients demonstrated a significantly higher serum IgA-anti-Fab activity than HIV-positive (HIV+) patients with AIDS-related complex (ARC) (P < 0.02), HIV+ patients without AIDS/ARC (P < 0.0001), HIV negative (HIV-) patients (P = 0.0001), or healthy controls (P < 0.0001). Moreover, an inverse association was observed between serum IgA-anti-Fab activity and CD4+ cell counts (r = -0.396, P < 10(-6)). This close association was confirmed in longitudinal studies of symptomatic patients. IgA-anti-Fab antibodies are suggested to play an important role in the immunopathogenesis of AIDS, and their determination may be helpful in the monitoring of HIV-infected patients.

Analysis of HLA-DR matching in DNA-typed cadaver kidney transplants

The effect of matching for HLA-DR antigens was analyzed retrospectively in 3455 cadaver kidney transplants that were typed by the DNA-RFLP method. HLA-DR matching improved the one-year graft survival rate significantly (P < 0.01). Importantly, in 718 first transplants in which the number of mismatches assigned by serological typing was different from that assigned by DNA typing, only the DNA results showed a significant impact of matching on graft outcome (P = 0.03). These results demonstrate that DNA typing is clinically relevant. We were unable to confirm that the HLA-DR6 specificity or the DR6-split DRB1*1302 are associated with poor graft survival.

Computer analysis of cadaver kidney allocation procedures

Data of 32,000 donors were utilized for a computer simulation to analyze the effect of selection parameters on the outcome of kidney transplants. If the HLA match grade is considered for organ allocation, the overall 1-year graft survival rate is up to 7% higher for first cadaver transplants and up to 12% higher for second transplants than if HLA matching is disregarded. This solely success-oriented organ allocation method, however, leads to prolonged waiting times for patients with rare HLA phenotypes. We developed a selection procedure that yields results near the theoretical optimum: 95% of all patients can be transplanted with 0-2 HLA-A, -B, -DR antigen mismatches, the average waiting time decreases to 20 months, and no patient needs to wait longer for a transplant than 6 years. The overall graft survival rate is only 0.4% lower than the rate obtainable with strictly HLA-oriented allocation. The method prevents "poorly matchable" patients from accumulating on the waiting list. Additionally, the unfavorable race ratio in the North American recipient pool can be largely normalized.

Defective IL-6 secretion in HIV-infected haemophilia patients

To study the role of IL-6 in HIV-induced B cell defects, in vitro B cell responses and IL-6 secretion were determined simultaneously in 67 haemophilia patients. Twenty-three patients were HIV- (Group 1), 27 HIV+ stage CDC II, III (Group 2), and 17 were HIV+ stage CDC IV (Group 3). Pokeweed mitogen (PWM) was used for T cell-dependent and Staphylococcus aureus Cowan I (SAC I) for T cell-independent B cell stimulation. B cell differentiation was assessed in a reverse haemolytic plaque assay and by ELISA determination of IgG and IgM in culture supernatants. An ELISA was used to measure IL-6 in plasma and culture supernatants. HIV- patients showed impaired immunoglobulin-secreting cell (ISC) responses after T cell-independent and T cell-dependent stimulation (P < 0.0001 and P < 0.01, respectively), whereas IL-6 secretion, IgM and IgG responses were comparable to those in healthy controls. HIV+ patients at stage CDC II, III or IV demonstrated significantly reduced mitogen-stimulated IL-6 secretion (P < 0.05, PWM; P < or = 0.001, SAC I) as well as impaired ISC and IgG responses (P < 0.01, PWM; P < or = 0.0001, SAC I). CDC IV patients showed reduced IgM responses in addition (P < 0.02, PWM; P < 0.0005, SAC I). Plasma IL-6 levels were elevated both in HIV+ patients (CDC II, III patients: 165 +/- 73 pg/ml, P < 0.005; CDC IV patients: 58 +/- 18 pg/ml, P < 0.0001) and in HIV- patients (283 +/- 65 pg/ml, P < 0.0001) which appeared to be a T cell effect induced by treatment with haemophilia factor concentrates. Our data provide evidence for different types of B cell deficiencies in HIV- patients (impaired ISC response only) and HIV+ patients (impaired ISC as well as IL-6 and IgM/IgG responses). The defective IL-6 secretion in HIV+ patients is likely to affect terminal B cell differentiation and this may explain the reduced immunoglobulin secretion in these patients in response to antigenic challenge.

CD4+ lymphocyte depletion in HIV-infected patients is associated with gp120-immunoglobulin-complement attachment to CD4+ cells

The mechanism of CD4+ lymphocyte depletion, which is the main immunological feature in HIV-infected patients, is unclear. We investigated whether gp120-immunoglobulin-complement complexes on the surface of CD4+ cells might be involved in the elimination of CD4+ lymphocytes. The results obtained in 63 HIV-infected patients show that gp120 is attached to a variable degree to CD4+ cells. Importantly, the percentage of CD4+gp120+ lymphocytes is inversely associated with CD4+ lymphocyte counts in the peripheral blood (p = 0.0004). CD4+gp120+ blood lymphocytes bind IgM (p = 0.0027) and IgG antibodies (p = 0.0001) and complement (p = 0.0005). These results suggest that immune complex-mediated cell elimination is an important mechanism of CD4+ cell depletion in patients with AIDS.