The association of kidney graft outcome with pretransplant serum IgG-anti-F(ab')2 gamma activity

Pretransplant sera of 474 kidney graft recipients were tested for IgG-anti-F(ab')2 gamma activity. The patients had significantly higher IgG-anti-F(ab')2 gamma activity than healthy controls (P = 0.0004). Serum lymphocytotoxic antibodies were correlated with IgG-anti-F(ab')2 gamma (P = 0.004), whereas CMV infection and blood transfusions were not. We found a significant association between pretransplant IgG-anti-F(ab')2 gamma activity and early and 1-year kidney graft outcome. This association was pronounced in recipients with no lymphocytotoxic antibodies. Recipients with immediately functioning grafts and a creatinine < 130 mumol/L at 1 year had strikingly higher pretransplant IgG-anti-F(ab')2 gamma activity than patients with graft failure (P < 0.0001).

Current status of HLA matching in renal transplantation. The Collaborative Transplant Study

The impact of HLA compatibility on the success rate of kidney transplants was studied in over 80,000 recipients of primary transplants. The transplants were done from 1982 to 1991 at over 300 transplant centers in 43 countries. The results show that matching the HLA chromosomes in related donor transplants has a striking influence. It is also important that matching for individual HLA antigens in cadaver transplants provides a highly significant improvement in graft survival (P less than 0.0001). After 5 years, matched grafts have a survival rate approximately 20% higher than completely mismatched grafts. The matching effect is particularly strong in presensitized and second graft recipients. There is now direct evidence that even if it is necessary to transport well-matched kidneys a long way, they have a significantly higher success rate than locally transplanted poorly matched kidneys. New data based on molecular technology show that the precise identification of HLA-DR antigens by DNA typing further improves the success rate of HLA-matched transplants.

Restriction mechanisms of B cell regulation by a physiological IgG-anti-immunoglobulin autoantibody

Immunization of LEW rats with strongly histoincompatible BN blood cells induces, in addition to anti-donor antibody, a broadly reactive IgG autoantibody which binds to IgG and IgM molecules (IgG anti-Ig). Minute amounts of affinity purified IgG anti-Ig (0.2 pg/10(6) cells) suppress the antibody production in vitro of antigen receptor (AgR)-stimulated B cells derived from rats of the same strain. The suppressive antibody is also active in the whole serum IgG fraction. Importantly, anti-Ig-induced suppression is governed by restriction mechanisms: only AgR-occupied B cells are affected, the suppression is cell cycle dependent, and maximum suppression is obtained at an optimum IgG concentration. Treatment of rats in vivo with 0.8 mg Ig-anti-Ig (whole IgG fraction) along with allogeneic cells resulted in nearly complete suppression of the anti-donor antibody response. Possible mechanisms of B cell suppression by IgG anti-Ig are crosslinking of AgR with FcR, or cocapping of the two receptors with sterical interaction as a consequence of their separate occupation. Both alternatives lead to the release of an inactivating signal.

Regulation of antibody response by an IgG-anti-Ig autoantibody occurring during alloimmunization. II. Selective inactivation of antigen receptor-occupied B cells

Heterologous antiimmunoglobulin antibodies are efficient regulators of the B cell response. We have shown that during the immune response against allogeneic cells the immune system develops autologous IgG-antiimmunoglobulin. A few molecules of this "physiological" autoantibody suppress the IgM production of one B cell in vitro. In the current series of experiments we further define the regulation of antigen receptor-activated B cells by this autoantibody. To mimic the in vivo situation, where IgG-anti-Ig appears a few days after alloimmunization, the antibody's effect on an already ongoing B cell response was studied. Interestingly, we found that the IgG-anti-Ig loses its suppressive effect when added to the cell culture 1 or 2 days after B cell activation, but that suppression can be completely restored when the cells are restimulated via their antigen receptor. Thus, the IgG-anti-Ig antibody suppresses B cells only when their antigen receptor is occupied. Even restimulated B cells become refractory 8 hr after activation, and later (24 hr) regain their susceptibility to IgG-anti-Ig-induced suppression. The Fc receptor is involved in mediating suppression since the antibody's suppressive capacity is abolished after removal of its Fc region. Possible mechanisms of B cell suppression by IgG-anti-Ig are crosslinking of antigen receptor with Fc receptor, or cocapping and functional interaction of the two receptors as a result of their separate occupancy. Our experiments demonstrate that B cell regulation by IgG-anti-Ig produced during an immune response to allogeneic cells is governed by 3 restriction mechanisms: antigen receptor occupancy, activation stage dependency, and optimal antibody concentration.

Regulation of antibody response by an IgG-anti-Ig autoantibody occurring during alloimmunization. I. A few IgG molecules inactivate one B cell

We have shown previously that alloimmunized rats develop a broadly reactive IgG-antiimmunoglobulin autoantibody in addition to antidonor antibodies. The findings presented herein demonstrate that this "physiological" antibody suppresses antigen receptor-induced IgM production of B cells derived from rats of the same strain. When affinity-purified IgG-anti-Ig was added to cell cultures, the antibody production of B cells was maximally inhibited at the minute concentration of 0.9 pg/10(6) cells. Higher or lower IgG-anti-Ig concentrations resulted in weaker suppression. The same result was obtained when spleen lymphocytes were used instead of purified B cells. Based on the molecular weight of IgG and Avogadro's number, our results indicate that a few molecules of IgG-anti-Ig are sufficient to inhibit the antibody production of a single B cell. Activity at this minuscule concentration demonstrates that IgG-anti-Ig antibodies are exquisitely active immunoregulatory molecules. In addition to the stimulatory effect of IgM-anti-Ig rheumatoid factors reported by others, our findings define the second component of an immunoregulatory mechanism: suppression of the B cell response by an IgG-anti-Ig autoantibody produced during alloimmunization.

Anti-IgG autoantibodies in HIV-infected hemophilia patients

Sera of 76 HIV-negative hemophilia patients, 103 HIV-positive (HIV+) hemophilia patients free of AIDS or AIDS related complex (ARC), and 32 HIV+ hemophilia patients with AIDS/ARC were tested for four different anti-IgG activities. IgG-anti-F(ab')2 gamma, IgM-anti-F(ab')2 gamma, and IgG-anti-Fc gamma serum activities were significantly associated with the clinical stage of HIV infection, whereas IgM-anti-Fc gamma was not. IgG-anti-F(ab')2 gamma activity was found to be caused by cross-reaction of anti-HIV antibody with an epitope within the constant CH1 domain of human IgG. HIV+ hemophilia patients with severe thrombocytopenia (less than 50,000/microliters platelet counts) had significantly higher IgM-anti-IgG activity than patients with greater than 50,000/microliters platelets. Because anti-IgG antibodies possess immunoregulatory properties, our results may serve as a possible explanation for the frequent B cell disorders encountered in HIV-infected patients.

Striking inverse association of IgG-anti-Fab gamma antibodies and CD4 cell counts in patients with acquired immunodeficiency syndrome (AIDS)/AIDS-related complex

The contribution of autoimmune phenomena to the pathogenesis of acquired immunodeficiency syndrome (AIDS) is poorly understood. We investigated the relationship between IgG-anti-Fab gamma autoantibodies and the main immunologic feature of AIDS, the decrease of CD4+ helper lymphocytes. Sera of 33 human immunodeficiency virus (HIV) infected (HIV+) hemophilia patients with AIDS/AIDS-related complex (ARC), 57 HIV+ patients without AIDS/ARC, 23 HIV-negative (HIV-) patients, and 76 healthy controls were tested for antibody activity against the Fab region of IgG. Patients with AIDS/ARC had significantly higher IgG-anti-Fab gamma activity than HIV+ patients without AIDS/ARC, HIV- patients, or controls (P less than .0001). A striking inverse association was found between IgG-anti-Fab gamma and CD4+ cell counts (r = -.69; P less than 10(-6)). Sequential testing in 16 AIDS/ARC patients showed that an increase in the IgG-anti-Fab gamma activity was invariably accompanied by a decrease in the CD4+ cell count. IgG-anti-Fab gamma antibodies may play an important role in the immunopathogenesis of AIDS.

Soluble IL-2 receptor and tumour necrosis factor-alpha in plasma of haemophilia patients infected with HIV

We measured plasma concentrations of soluble receptors for IL-2 (sIL-2R) and tumour necrosis factor-alpha (TNF-alpha) in 149 haemophilia patients. Soluble IL-2R levels were elevated in 37% of 62 HIV-seronegative patients (mean 570 +/- 27 U/ml versus 361 +/- 17 U/ml in the control group, P less than 0.0001), in 78% of 68 HIV-seropositive patients (928 +/- 49 U/ml, P less than 0.0001), and in 95% of 19 AIDS/ARC patients (1578 +/- 199 U/ml, P less than 0.0001 compared with controls and with HIV-seronegative patients; P less than 0.005 compared with HIV-seropositive asymptomatic patients). A negative correlation was observed between sIL-2R, relative and absolute numbers of CD4+ cells (P less than 0.0001), and CD4/CD8 ratios (P less than 0.0001). There was also a negative correlation between sIL-2R in plasma and the cellular expression of IL-2R (P less than 0.001). We found a significant association of sIL-2R and plasma neopterin (P less than 0.0001). With progression of the disease from HIV-seronegative to seropositive without symptoms and to full manifestation of AIDS/ARC, sIL-2R plasma levels increased. The highest levels were found at the time of diagnosis of AIDS/ARC, but the levels decreased again during the following 18 months. Eight per cent of HIV-seronegative patients, 32% of HIV-seropositive patients, and 24% of patients with AIDS/ARC had increased plasma TNF-alpha. We conclude that sIL-2R and TNF-alpha plasma levels are elevated in HIV-infected haemophilia patients and that sIL-2R is a marker for disease progression from asymptomatic HIV-seropositive to AIDS/ARC.

Autoantibodies in HIV-infected hemophilia patients against different epitopes on CD4+ lymphocytes and recombinant CD4

We studied 684 sera obtained from 20 hemophilia patients with AIDS/AIDS-related complex (ARC), 89 asymptomatic HIV+, 76 HIV- hemophilia patients and 151 healthy controls for antibodies against recombinant CD4 (rCD4). Twenty-two percent of AIDS/ARC patients, 10% of asymptomatic HIV+ patients, 17% of HIV-patients, and 1% of healthy controls had anti-rCD4 antibodies. Purified anti-rCD4 antibodies did not react with human CD4+ lymphocytes. This may explain why formation of anti-rCD4 antibodies correlated neither with the occurrence of autoantibodies against CD4+ lymphocytes nor with a decrease in CD4+ cell counts. Antibodies that were eluted from CD4+ lymphocytes after sequential adsorption and elution with separated CD8+ and CD4+ cells reacted with CD4+ lymphocytes of only some healthy individuals, suggesting diversity of CD4 expression.

DNA typing: an important step forward? Collaborative Transplant Study

In a collaborative project which was supported by 96 transplant centers, DNA typing of HLA-DR antigens was carried out on over 7,000 transplant donors and recipients at 8 participating laboratories. Approximately 25% of the individuals were found to have been typed incorrectly by serological means. An analysis of over 2,500 first cadaver kidney transplants showed a significant correlation of matching for the HLA-DR antigens in transplants where the serological typing was confirmed by DNA typing. In transplants where the serological typing was found to be incorrect, the analysis of serological HLA-DR mismatches resulted in no correlation with graft outcome whereas a significant correlation was found when the corrected DNA typed HLA-DR antigens were analyzed. Transplants which had been reported to the Collaborative Transplant Study based on serological typing as matched for HLA-A, -B, -DR or HLA-B, -DR were found to have a superior graft survival rate only if HLA-DR compatibility was confirmed by DNA typing.

An immunoglobulin-specific autoantibody occurring during alloimmunization suppresses the antibody response

Our previous studies showed that a broadly reactive immunoglobulin G (IgG) anti-immunoglobulin (IgG-anti-Ig) autoantibody is induced during the immune response of LEW rats to BN blood cells. The present experiments analyze the immunoregulatory effect of this physiological autoantibody on antigen receptor-activated B cells in cell cultures. The results show that: (a) At 0.9 pg IgG-anti-Ig/10(6) B cells, an almost complete suppression of the antibody response is induced: we calculated that a few IgG-anti-Ig molecules are sufficient to suppress the antibody response of one B cell; (b) IgG-anti-Ig-induced B-cell suppression is dose-dependent; (c) IgG-anti-Ig suppresses B cells contained in their natural environment (mixed spleen cell population). These data demonstrate that the IgG-anti-Ig autoantibody is an extremely efficient regulatory molecule of the alloimmune response.

Strength of HLA-A, HLA-B, and HLA-DR mismatches in relation to short- and long-term kidney graft survival. Collaborative Transplant Study

The separate influence of HLA-A, HLA-B, and HLA-DR mismatches on short- and long-term kidney graft survival was analyzed in a series of over 40,000 recipients of first cadaver kidney transplants. As expected, during the early posttransplant period, HLA-DR mismatches had a stronger influence on graft survival than HLA-B mismatches, and HLA-A mismatches had a very small influence. Surprisingly, during the period from 6 months to 5 years post transplantation, all three HLA loci had approximately the same influence. When the graft survival computation was started at 100% at 6 months, the difference between grafts with zero or two mismatches at the end of 5 years was 6%, regardless of whether HLA-A, HLA-B, or HLA-DR antigens were analyzed. The influence of the three loci was additive so that the survival rate difference between transplants with zero or six mismatches for HLA-A, -B, -DR was 17% at 5 years. We concluded that, although the HLA-A locus exerts only a weak influence during the early posttransplant course, its influence on long-term survival is comparable to that of HLA-B and HLA-DR. In order to obtain optimal long-term survival, all three loci must be considered in the donor-recipient matching procedure.

Pretransplant serum IgG-anti-F(ab')2gamma activity and kidney graft outcome: comparison of results obtained at two centers

Anti-IgG autoantibodies are reported to possess immunoregulatory properties. In the present study, we investigated the effect of pretransplant serum IgG-anti-F(ab')2gamma autoantibody activity on kidney graft outcome in recipients from two transplant centers.

Improving CD4+ lymphocyte counts in HIV-infected hemophilia patients. A favorable prognostic indicator?

CD4+ lymphocyte counts of 91 HIV+ hemophilia patients were monitored for a mean of 4 years (range: 15-69 months). CD4+ lymphocytes decreased in 55 but increased in 36 patients over time. The CD4+ cell increases were persistent in 5 patients, whereas they fluctuated in 31. Of the 36 patients with increasing CD4+ counts 3 developed AIDS and 1 LAS. The other 32 patients were clinically asymptomatic (CDC II), but had immunological abnormalities, such as increased serum neopterin (N = 18) and impaired in vitro T cell responses to pooled allogenic stimulator cells (N = 15) or mitogens (N = 18). In contrast, of the 55 patients whose CD4+ cells decreased, 24 developed AIDS and 5 ARC (P less than 0.0005). Only 2 of these 55 patients had normal mitogen stimulation in vitro and normal serum neopterin levels.

Survival of DNA HLA-DR typed and matched cadaver kidney transplants. The Collaborative Transplant Study

The clinical value of serological HLA matching for cadaver kidney transplantation remains uncertain because the success rate for HLA-matched cadaver transplants is lower than that of HLA-matched sibling grafts. Up to 25% of serological HLA-DR typings may be incorrect when compared with a more accurate DNA-RFLP method, and we have now examined whether incorrect HLA-DR typings account for the lower than expected success rates of HLA-matched cadaver transplants. 58 transplant centres took part in this study and DNA was extracted from over 4000 samples of frozen tissue at the study centre. 8 laboratories then completed blind RFLP typing for HLA-DR. Serological typing data were reported by individual transplant laboratories. 29 of 107 transplants (27%) that were reported as HLA A, B, DR compatible and 76 of 273 (28%) transplants that were reported as HLA B, DR compatible according to serological typing were found to be HLA-DR mismatched by DNA typing. The one-year transplant success rate for DNA-matched HLA, A, B, DR grafts was 87% compared with 69% for mismatched grafts (p less than 0.02); the corresponding success rate for DNA-matched HLA B, DR grafts was 85% compared with 72% for mismatched grafts (p less than 0.01). Many transplants that were previously thought to be HLA matched are mismatched, and this finding may account for previously unexplained graft failures.

Hepatitis C-virus (HCV) antibodies in patients after kidney transplantation

The hepatitis C-virus (HCV) is the main etiologic agent of posttransfusion hepatitis (PTH). Most patients depending on hemodialysis need transfusion of blood before kidney transplantation. Of 272 patients after kidney transplantation, 27 (10%) were found to be anti-HCV-ELISA-positive (HCV-Antibody-ELISA, Ortho Diagnostics). The antibodies could be neutralized by HCV C-100-3 antigen. Eight of 22 patients (36%) who had more than one kidney transplantation were classified anti-HCV positive [30% (8/27) of all anti-HCV positive patients]. The number of transfused blood units ranged from 0 to 99 BU. Receiving more than one kidney graft or the transfusion of more than 5 units of blood increased the risk for HCV infection 3.5 or 4.1 times, respectively, compared with one transplantation or less than 5 units of blood. No significant interactions were seen between these two variables. Of the anti-HCV positive patients, 48% were anti-HBc negative as well as HBs-antigen negative, 52% were anti-HBc positive.

Autoantibodies against CD4 cells are associated with CD4 helper defects in human immunodeficiency virus-infected patients

To investigate whether autoantibodies against CD4-positive lymphocytes might induce helper dysfunction, autoantibody formation and T-cell function was examined simultaneously in 61 hemophilia patients. Twenty patients were human immunodeficiency virus (HIV)-negative, 26 HIV-positive stage CDC II or III, and 15 were HIV-positive stage CDC IV. T lymphocytes, CD4-positive, or CD8-positive T subsets were cocultured with B lymphocytes and pokeweed mitogen (PWM) for 6 days and Ig-secreting cells were assessed in a reverse hemolytic plaque assay. The presence of IgM, IgG, C3d, or gp120 on the surface of T cells or T subsets was analyzed by flow cytometry. Autoantibodies against CD4-positive T cells were not detected in controls or HIV-negative patients, but were common in HIV-positive patients (20 of 41 patients). In patients with autoantibodies we found an increased incidence of CD4 helper defects (P less than .0001 in CDC II or III patients; P less than .02 in CDC IV patients). 12 of 13 patients with IgM autoantibodies and 4 of 4 with IgG autoantibodies showed CD4 helper defects. Complement fixation had no relevance. Autoantibody formation against CD4 cells was not due to increased in vivo B-cell stimulation (spontaneous plaque formation: 611 +/- 204 PFC/10(6) B cells in autoantibody-negative patients v 650 +/- 202 PFC/10(6) B cells in autoantibody-positive patients; not significant). Thus, our results suggest that autoantibody formation is not caused by a general state of in vivo B-cell activation. Rather, the production of autoantibodies appears to coincide with defects in B-cell proliferation or differentiation, as shown by reduced mitogen-stimulated B-cell responses in CDC II and III patients (P less than .05). Autoantibodies against CD4 cells appear to be involved in the pathogenesis of CD4 helper defects of HIV-infected patients.