Fetomaternal leukocyte incompatibility

Abortion may sensitize the mother to HLA antigens

The incidence of cytotoxic antibodies in relation to histories of abortions was analyzed in sera from 474 nulliparous pregnant women. In patients with previous spontaneous abortions, there is a higher incidence of positive sera than in primigravidae. Furthermore, patients with two or more prior abortions show a greater incidence of cytotoxic activity in their sera than women who have had only one abortion.

Birth order and the severity of illness in schizophrenia

A proposed risk factor for schizophrenia is materno-foetal incompatibility. We tested the hypothesis that, in multiply affected families, later born children would exhibit a more severe form of schizophrenia than their older siblings. The effect of birth order on (1) severity of the worst ever episode of illness; (2) deterioration from premorbid level of functioning; (3) age of onset; (4) response to medication; and (5) illness course, was assessed in 150 sibling pairs with schizophrenia and schizoaffective disorder. We found that later birth order reduced the likelihood of regaining the premorbid level of functioning after an acute episode and was also associated with an earlier age of presentation. This study lends some support to the hypothesis that later birth order results in a more severe form of the disorder, although there are other possible explanations for our findings. Further work is needed to explore the possibility of maternal-foetal genotype incompatibility as a risk factor for schizophrenia.

HistoCheck. Evaluating structural and functional MHC similarities

The HistoCheck webtool provides clinicians and researchers with a way of visualizing and understanding the structural differences among related major histocompatibility complex (MHC) molecules. In the clinical setting, human leukocyte antigen (HLA) matching of hematopoietic stem cell donors and recipients is essential to minimize "graft versus host disease" (GvHD). Because exact HLA matching is often not possible, it is important to understand which alleles present the same structures (HLA-peptide complexes) to the T-cell receptor (TCR) despite having different amino acid sequences. HistoCheck provides a summary of amino acid mismatches, positions, and functions as well as 3-dimensional (3D) visualizations. In this chapter, we describe how HistoCheck is used and offer advice in interpreting the query results.

Humoral immune response after kidney transplantation is enhanced by acute rejection and urological obstruction and is down-regulated by mycophenolate mofetil treatment

The anti-allograft immune response may have a cellular and a humoral component. Lymphocytotoxic antibodies (Ab) and anti-human leucocyte antigen (HLA) Ab present before kidney transplantation carry an enhanced risk of acute rejection. Current immunosuppressive drugs act predominantly upon the cellular immune pathway which may leave unopposed the humoral mechanisms of anti-allograft response. We studied the production of lymphocytotoxic Ab and anti-HLA Ab after kidney transplantation under different drug therapies. Two hundred and sixty-four consecutive kidney transplant recipients treated with different immunosuppressive drugs, either stable and or with previous acute rejection or acute urologic obstruction, entered this study. Lymphocytotoxic Ab and anti-HLA Ab were evaluated by complement-dependent cytotoxicity and by ELISA. Ab donor-specificity was determined by flow cytometry. Both lymphocytotoxic Ab and anti-HLA Ab were significantly increased in acute rejection whatever the immunosuppressive regimen and almost significantly in urologic obstruction treated with azathioprine (AZA) groups. The presence of antidonor-specific Ab was associated with a significantly higher rate of graft loss. Mycophenolate mofetil (MMF) therapy significantly down-regulated Ab synthesis in all patients groups when compared with AZA. The development of humoral antidonor response post-transplantation is associated with a dismal graft prognosis. This is the first report that acute urologic obstruction may be followed by unspecific lymphocytotoxic and anti-HLA Ab synthesis, surmising that a protracted obstruction may promote renal fibrosis through antibody mediation. The significant down-regulation of the humoral response by MMF when compared with AZA may herald a lower risk to mount a chronic rejection process.

Chimerism and tolerance in transplantation

Studies in experimental models (1953-1956) demonstrated that acquired donor-specific allotolerance in immunologically immature or irradiated animals is strongly associated with donor leukocyte chimerism. Bone marrow transplantation in immune-deficient or cytoablated human recipients was a logical extension (1968). In contrast, clinical (1959) and then experimental organ transplantation was systematically accomplished in the apparent absence of leukocyte chimerism. Consequently, it was assumed for many years that success with organ and bone marrow transplantation involved fundamentally different mechanisms. With the discovery in 1992 of small numbers of donor leukocytes in the tissues or blood of long-surviving organ recipients (microchimerism), we concluded that organ engraftment was a form of leukocyte chimerism-dependent partial tolerance. In this initially controversial paradigm, alloengraftment after both kinds of transplantation is the product of a double immune reaction in which responses, each to the other, of coexisting donor and recipient immune systems results in variable reciprocal clonal exhaustion, followed by peripheral clonal deletion. It was proposed with Rolf Zinkernagel that the individual alloresponses are the equivalent of the MHC-restricted T cell recognition of, and host response to, intracellular parasites and that the mechanisms of immune responsiveness, or nonresponsiveness, are governed by the migration and localization of the respective antigens. Elucidation of the mechanisms of nonresponsiveness (clonal exhaustion-deletion and immune ignorance) and their regulation removed much of the historical mystique of transplantation. The insight was then applied to improve the timing and dosage of immunosuppression of current human transplant recipients.

The contribution of HLA genes to IBD susceptibility and phenotype

The human leukocyte antigen (HLA) region located on chromosome 6p encodes the highly polymorphic, classical class I and II genes essential for normal lymphocyte function; it also encodes a further 224 genes. Many early studies investigating this region were limited by small sample size, poor statistical methodology, population stratification and variable disease definition. Although more recent studies have improved study design, investigators are still challenged by the complex patterns of linkage disequilibrium across this gene-dense region, and by the disease heterogeneity characteristic of all genetically complex disorders. However, a number of important observations have emerged from recent studies: (1) the HLA harbours gene(s) that determine susceptibility to colonic inflammation in both ulcerative colitis (UC) and Crohn's disease (CD); (2) most of the specific associations with UC and CD appear to differ; (3) associations between different ethnic groups differ; (4) markers in the HLA might predict the course of disease and the development of complications, notably the extraintestinal manifestations of disease.

Are preformed antibodies to biliary epithelial cells of clinical importance in liver transplantation?

During acute liver allograft rejection, most of the tissue damage to bile duct epithelium is thought to occur as a consequence of direct immunologic injury by T-cell-mediated immune effector mechanisms. However, the role of antibodies to biliary epithelial cells (BECs) in liver transplant rejection is not known. We therefore investigated cross-match sera obtained immediately before liver transplantation from 95 patients for the presence of BEC-reactive antibodies to determine their association with acute rejection. BECs were isolated from one normal healthy liver. Antibody binding was detected by using flow cytometric analysis. Donor lymphocyte-specific cross-matches using complement-dependent cytotoxicity (CDC) and flow cytometric assays also were performed. The 2-year patient survival rate in this study was 86.3%. Eleven patients were positive for either CDC or flow cytometric cross-matches. BEC antibodies were detected in 41 serum samples (43.2%). Patients with BEC antibodies experienced acute rejection more frequently (65.9%) compared with 42.5% without antibodies (P <.03). HLA specificity determinations indicated that in 5 of 41 cases, anti-BEC reactivity was caused by HLA antibodies. No correlations between the presence of BEC antibodies and patient survival and the occurrence of cholangitis and nonsurgical bile duct strictures were found within 2 years of follow-up. In conclusion, preformed antibodies to BECs are associated with acute rejection. Thus, the presence of these antibodies before transplantation may facilitate acute liver graft rejection.

Significance of positive cytotoxic cross-match in adult-to-adult living donor liver transplantation using small graft volume

A positive cross-match in cadaveric liver transplantation is relatively acceptable, but its role in living donor liver transplantation (LDLT) is less well known. The aim of this study is to examine the significance of cytotoxic cross-match in adult-to-adult LDLT using small-for-size grafts. Forty-three adult-to-adult LDLTs were performed at Seoul National University Hospital (Seoul, Korea) from January 1999 to July 2001. Subjects consisted of 27 men and 16 women with an average age of 45.4 years. Average liver graft weight was 565.3 +/- 145.7 g, and average graft-recipient weight ratio (GRWR) was 0.89% +/- 0.20%. HLA cross-match testing by lymphocytotoxicity and flow cytometry was performed routinely preoperatively. Factors that may influence survival, such as age; sex; blood group type A, type B, type O compatibility; cytotoxic cross-match; donor age; surgical time; cold ischemic time; and GRWR, were analyzed. Nine patients (20.9%) died in the hospital. There was a greater in-hospital mortality rate in women than men (37.5% v 11.1%; P = .049). The extra-small-graft group (0.54% < or = GRWR < 0.8%; n = 14) showed greater in-hospital mortality rates than the small-graft group (0.8% < or = GRWR < or = 1.42%; n = 29; 42.9% v 10.3%; P = .022). A positive cross-match was detected in 4 women transplant recipients, and 3 of these patients belonged to the extra-small-graft group. All patients with a positive cross-match died of multiorgan failure after early postoperative acute rejection episodes. Positive cross-match was the only significant factor in multivariate analysis (P = .035). In conclusion, when lymphocytotoxic cross-match and flow cytometry are significantly positive, adult-to-adult LDLT using small-for-size grafts should not be performed.

HLA-specific alloantibodies and renal graft outcome

HLA-specific humoral immunity, as a result of recipient allosensitization, induces hyperacute rejection of allogenic kidney grafts. Cross-match tests are performed to avoid this complication. However, current techniques do not allow determination of HLA-specificity of donor-reactive antibodies in the acute cadaver-donor situation. New methods are described and discussed in this report as well as the alloantibody specificities that are of clinical importance. Alloantibodies not only mediate hyperacute rejection but may also participate in the acute rejection of organ grafts. Clinical associations between early immunological complications, such as acute rejection, in heart, liver and kidney allografted patients and pre-transplantation humoral alloimmunity emphasize the need for proper determination of donor-specific humoral immunity prior to transplantation.

Historic landmarks in clinical transplantation: conclusions from the consensus conference at the University of California, Los Angeles

The transplantation of organs, cells, and tissues has burgeoned during the last quarter century, with the development of multiple new specialty fields. However, the basic principles that made this possible were established over a three-decade period, beginning during World War II and ending in 1974. At the historical consensus conference held at UCLA in March 1999, 11 early workers in the basic science or clinical practice of transplantation (or both) reached agreement on the most significant contributions of this era that ultimately made transplantation the robust clinical discipline it is today. These discoveries and achievements are summarized here in six tables and annotated with references.

Natural killer cell cytotoxicity and paternal lymphocyte immunization in women with recurrent spontaneous abortions

PROBLEM

Natural killer (NK)-cell cytotoxicity in women undergoing lymphocyte immunization prior to and following treatment was investigated.

METHOD OF STUDY

A cohort of 33 women with a history of two or more recurrent spontaneous abortions was prospectively studied. NK-cell cytotoxicity was determined at effector-to-target ratios of 50:1 and 25:1. Peripheral blood CD56+ NK-cell, CD19+ B-cell, CD19+/5+ B-1-cell, and CD3+ pan T-cell levels were studied by flow cytometry before and after lymphocyte immunization treatment. Maternal antipaternal T- and B-cell antibody levels were measured before and after lymphocyte immunization by flow cytometric analysis. Paternal lymphocyte immunizations were given two times with a 4-week interval. Post-lymphocyte immunization testing was done 4 weeks after the second lymphocyte immunization. The controls were 8 normal healthy women. NK assays were done twice with an interval of 8 weeks.

RESULTS

NK-cell activity at effector-to-target ratios of 50:1 (P = 0.005) and 25:1 (P = 0.001) were significantly suppressed after lymphocyte immunization. CD3+ pan T-cell levels after lymphocyte immunization were significantly increased compared with levels before lymphocyte immunization (P = 0.008). CD56+ NK-cell levels were significantly suppressed after lymphocyte immunization (P = 0.016). There was no correlation between changes in NK cytotoxicity and differences in antipaternal lymphocyte antibody levels before or after lymphocyte immunization.

CONCLUSION

Lymphocyte immunization suppresses NK-cell cytotoxicity and CD56+ NK-cell levels and increases the peripheral blood CD3+ T-cell population in women with recurrent spontaneous abortions.

Human leukocyte antigen system and the immune response to it

Immunologic rejection of tissue grafts follows recognition of donor alloantigens; either those resulting from ABO incompatibility of those encoded by the human major histocompatibility complex, HLA. Alloantigens encoded by HLA are present on membrane proteins that are expressed constitutively by tissues or whose expression can be induced by cytokines released during inflammation. Genes of the HLA complex are highly polymorphic resulting in variations in amino acid sequence that shape the peptide binding pocket of HLA molecules and define the complementary structure that interacts with the T lymphocyte receptor for antigen. Variants of HLA proteins expressed by the allografts that are not expressed by the recipient can stimulate the immune response to the allograft resulting in rejection both by humoral antibody and through attack by T lymphocytes. Class II HLA antigens on donor cells can stimulate these responses directly by contact with recipient T cells. However, rejection also may result when HLA antigens are released from the graft, processed to peptides, and presented to recipient T cells by cells expressing recipient HLA Class II molecules. Rejection can be avoided by preventing activation of T lymphocytes, by minimizing differences in HLA proteins between recipient and donor or by avoiding preexisting responses to donor HLA antigens.

Influence of anti-HLA antibodies and positive T-lymphocytotoxic crossmatch on survival and graft rejection in human liver transplantation

BACKGROUND/AIMS

The role of crossmatching in liver transplantation is controversial. The aim of this study was to investigate retrospectively the effect of sensitization and IgG lymphocytotoxic crossmatching on liver transplantation.

METHODS/RESULTS

Over 5 years, 20 of 243 (8.2%) first liver transplants were performed with a positive crossmatch and their outcome was compared with the remaining 223 performed with a negative crossmatch. Women had a higher incidence of positive crossmatch than men (p < 0.001). Significant differences in mean panel reactive antibody of 2.7% and 43.3% were found in negative and positive crossmatch patients, respectively (p < 0.001). Severe early rejection resulting in graft loss occurred in eight of 20 positive crossmatch patients, and only one of 223 negative crossmatch patients (p < 0.001). Five of the remaining positive crossmatch patients suffered several acute rejection episodes some months after liver transplantation. Two of 20 in the positive crossmatch group developed chronic rejection (10%) compared with ten of 223 negatives (4.4%) (N.S). Nine of 16 positive crossmatch female recipients suffered graft loss and seven died, representing 1-year graft and patient survival of 56% and 43%, respectively. Fifteen of 68 negative crossmatch female recipients presented graft loss and 12 died, accounting for 1-year patient and graft survival of 82% and 78% (p < 0.005), respectively. Five patients (20%) displayed positive crossmatch at the time of retransplantation, compared with 24 (10%) who were negative (N.S).

CONCLUSION

Our experience confirms the adverse impact of a positive crossmatch in liver transplantation, particularly in female recipients. Candidates with high panel reactive antibody are more likely to display a positive crossmatch, and therefore to develop early severe rejection and graft failure.

The immunogenetics of bone marrow transplantation

It is now clear that it is not necessary to use an HLA genotypically identical donor to have a successful marrow transplant. However, it is equally clear that the likelihood of complications increases with each increment in histoincompatibility. The implication is that histocompatibility testing must be of the highest possible precision to choose the optimal donor, and to predict the risk of adverse alloreactivity. Most clinicians would seriously consider transplantation from a one locus-mismatched relative or an HLA-matched unrelated donor in virtually any situation in which transplantation from a matched sibling would be felt to be the standard of care. More thought would need to go into transplantation from a two or three locus-mismatched relative or a mismatched unrelated donor.

MHC class II compatibility in aborted fetuses and term infants of couples with recurrent spontaneous abortion

Maternal-fetal histocompatibility for alleles at HLA class II loci, HLA-DQA1 and HLA-DQB1, was examined in 40 abortuses and 31 liveborn children of 68 couples with a history of idiopathic recurrent spontaneous abortion (RSAB) who underwent leukocyte immunization prior to the index pregnancy. Significantly more couples with RSAB shared two HLA-DQA1 alleles as compared with fertile control couples (0.18 vs. 0.03, respectively; P = 0.031). There were no differences in HLA sharing between couples with RSAB who experienced a repeat abortion in the index pregnancy as compared with couples with RSAB who were delivered of a liveborn child. Non-significant deficits of abortuses who were compatible for alleles at the HLA-DQA1 (6 observed vs. 8.5 expected; P = 0.225) and the HLA-DQB1 (7 observed vs. 9.2 expected; P = 0.254) loci were observed. A significant deficit of HLA-DQA1 compatible liveborn children was observed (1 observed vs. 5.5 expected; P = 0.0069). The overall deficit of HLA-DQA1 compatible fetuses (7 observed vs. 14.0 expected; P = 0.0018) after approximately 8 weeks gestation suggests that HLA-DQA1 compatible fetuses may be aborted early in pregnancy, prior to the time when fetal tissue can be recovered for genetic studies.

Induction of B cell unresponsiveness to noninherited maternal HLA antigens during fetal life

Patients who have received many transfusions become highly sensitized and develop antibodies against almost all HLA alloantigens, so that finding a cross-match negative kidney donor is difficult. A survey of those patients showed that 50 percent did not form antibodies against the noninherited maternal HLA antigens. Apart from the obvious clinical implications, the data indicate that a human equivalent of murine neonatal or actively acquired tolerance has now been identified.

Effects of serum versus plasma on agglutination of antibody-coated indicator cells by human rheumatoid factors

Plasma and serum contain an inhibitor (I) of the agglutination of rabbit IgG-coated sheep erythrocytes by human rheumatoid factor (RF). Plasma but not serum contains an inhibitor of the inhibitor (I/I) which allows RF to interact with its target. In normal blood, there is more I than I/I, and I can be removed by solid-phase chromatography through concanavalin A (Con A). Plasma I/I is heat labile being eliminated by heating at 56 degrees C for 30 min. Addition of exogenous calcium clots EDTA plasma, causing an irreversible loss of I/I, and suggesting its involvement in the clotting cascade. The absence of I/I from Factor V-deficient plasma and destruction of I/I by Russell's viper venom indicate I/I either is associated with or is a part of Factor V. These findings suggest a balanced interplay between I and I/I, and indicate results of immunological tests done in vitro may not accurately reflect immune function in vivo. This seems to represent an unexplored link between hemostasis and immunity.

Enhanced phagocytosis of mononuclear phagocytes in pregnancy

The phagocytic activity of peripheral blood mononuclear phagocytes for Staphylococcus epidermis of healthy non-pregnant and pregnant women throughout pregnancy was examined in relation to gestational age. The study included 30 healthy non-pregnant women and 90 healthy pregnant women equally distributed across the three trimesters. Two variables were investigated: the number of mononuclear cells in phagocytosis and the average number of bacteria per monocyte in phagocytosis. As pregnancy progressed a gradual and significant increase was found in the number of monocytes in phagocytosis and a significantly higher proportion of macrophages with six or more bacteria per phagocyte.

Antibody responses in secondary aborting women: effect of inhibitors in blood

The perpetually high antipaternal and cell panel antibody reactivity in the blood of secondary aborting patients sets them apart from most multigravid or multiparous women. Our studies with secondary aborters' sera have shown their complement-dependent cytotoxicity (CDC) reactivity to be abolished by heat treatment (56 degrees C for 30 min) or by solid phase heparin absorptions. This is only observed if treated serum is present; a wash step restores optimal CDC activity. Thus, something in their treated serum not associated with antibody-binding to target cells is inhibiting CDC activity. A similar inhibitor was found in all human sera tested. Anticomplementary effects were excluded by showing that CDC with horse antihuman leukocyte antibody was not affected by these inhibitors. To investigate this inhibition, we designed a hemagglutination assay (HA) employing rabbit IgG-coated sheep erythrocytes and human rheumatoid factor. The results of these studies show the presence of an inhibitor (I) to both CDC and HA in normal plasma and serum. Of special interest was the presence of a heat-labile inhibitor of the inhibitor (I/I) in plasma, but not in serum. Biochemical characterization of the I is in progress. The I/I in plasma appears to be factor V of the clotting system. These observations represent a link between the immune system and clotting mechanisms, which may be important in understanding the pathophysiology of secondary abortion.

Organ transplantation with special emphasis on Cyclosporin A

The history of organ transplantation and the development of immunosuppression therapy were discussed in detail, starting from Medawar's acquired immunological tolerance theory. The current status of transplantation of organs including the kidney, heart, liver and pancreas was reviewed. Current concepts of immunosuppression were discussed, with special emphasis on the use of Cyclosporin A.

Incidence of neutrophil antigens on human cord neutrophils

Neutrophils isolated from cord blood of healthy newborns (33 blacks and 21 whites) were investigated by EDTA-microagglutination for their expression of neutrophil specific antigens that have been associated with isoimmune neonatal or autoimmune neutropenia. Equal volumes of various neutrophil antisera (2 microliter) and cord neutrophils (3-5 X 10(6)/ml) were mixed in tissue typing microplates under oil and were incubated at room temperature for 6-8 hr, following which the degree of agglutination was noted. Our data revealed that all the currently recognized neutrophil antigens are readily demonstrable by antineutrophil antibodies in cord blood, (NA1, 52-54%; NA2, 81-85%; NB1, 95-96%; NC1, 90%; 9A, 29-30%) suggesting that neutrophil antigens are fully expressed at birth.