Soluble HLA class I in the serum of transplant recipients

Soluble HLA-I and HLA-II Molecules Are Potential Prognostic Markers of Progression of Systemic and Local Inflammation in Patients with COPD

Soluble molecules of the major histocompatibility complex play an important role in the development of various immune-mediated diseases. However, there is not much information on the participation of these proteins in the pathogenesis of chronic obstructive pulmonary disease (COPD). The aim of our work was to determine the content of soluble molecules of the major histocompatibility complex of classes I and II (sHLA-I and sHLA-II) in the exhaled breath condensate (EBC) and in the blood serum in patients with moderate to severe COPD during the exacerbation and stable phase. We investigated 105 patients (male) with COPD aged 46-67 and 21 healthy nonsmoking volunteers (male) comparable in age. The content of sHLA-I and sHLA-II molecules was studied using ELISA. We found an increase in the level of sHLA-I and sHLA-II molecules in EBC, as well as an enhancement in the serum content of sHLA-II in all the examined COPD patients compared to healthy nonsmoking volunteers. The revealed negative correlation between the serum concentration of sHLA-II and values of FEV1 and FEV1/FVC in all examined patients with COPD gives a possibility to consider the content of these proteins as an additional systemic marker of disease severity. The maximum endobronchial and serum concentrations of sHLA-I and sHLA-II were detected in patients with severe COPD during the exacerbation. The negative associations between the content of these molecules in EBC and serum and the parameters of lung function in patients with severe COPD were established. These findings suggest a pathogenetic role of sHLA-I and sHLA-II molecules in the mechanisms of the development and progression of local and systemic inflammation in COPD.

Allostimulatory capacity of conditionally immortalized proximal tubule cell lines for bioartificial kidney application

Novel renal replacement therapies, such as a bioartificial kidney (BAK), are needed to improve current hemodialysis treatment of end-stage renal disease (ESRD) patients. As BAK applications may reveal safety concerns, we assessed the alloimmunization and related safety aspects of readily available conditionally immortalized human proximal tubule epithelial cell (ciPTEC) lines to be used in BAK. Two ciPTEC lines, originally derived from urine and kidney tissue, were characterized for the expression and secretion of relevant molecules involved in alloimmunization and inflammatory responses, such as HLA class-I, HLA-DR, CD40, CD80, CD86, as wells as soluble HLA class I and proinflammatory cytokines (IL-6, IL-8 and TNF-α). A lack of direct immunogenic effect of ciPTEC was shown in co-culture experiments with peripheral blood mononuclear cells (PBMC), after appropriate stimulation of ciPTEC. Tight epithelial cell monolayer formation on polyethersulfone flat membranes was confirmed by zonula occludens-1 (ZO-1) expression in the ciPTEC tight junctions, and by restricted inulin-FITC diffusion. Co-culture with (activated) PBMC did not jeopardize the transepithelial barrier function of ciPTEC. In conclusion, the absence of allostimulatory effects and the stability of ciPTEC monolayers show that these unique cells could represent a safe option for BAK engineering application.

Successful kidney transplant in a patient with IgG anti HLA Class-I auto-antibodies: a case report

Donor specific antibodies (DSA) play a significant role in graft rejection. Many laboratory methods, varied in sensitivity and specificity, are used to detect them. We report a case of a 38-year-old man presented with end stage renal disease considered for kidney transplantation. He had no history of blood transfusions nor transplantation procedures. Dilemma rose when he got multiple positive crossmatches with matching donors and a positive autologous crossmatch due to IgG anti HLA auto-antibodies, which are at the same time against matched donors. Since positive crossmatch is a contraindication for transplant, we couldn't perform transplant from any matched donor. Therefore, we considered a total mismatched donor then transplantation was performed. Observation after surgery showed normalization of creatinine, blood pressure and a good function of the planted allograft for two years of follow up.

Soluble HLA class I molecules exert differentiated influence on renal graft condition

The function of soluble HLA (sHLA) antigens in the process of immunoregulation and especially in graft tolerance versus rejection has not yet been established. It has been suggested that donor-derived sHLA may exert an immunotolerant influence on the graft. We sought to determine the role of sHLA class I in kidney graft survival by evaluating the influence of these molecules on allotypic lymphocytotoxic antibodies and the concentration of gamma interferon (INF-gamma). Analysis of sHLA was performed indirectly utilizing their ability to inhibit lymphocytotoxic reaction dependent on complement activation. To demonstrate the inhibitory properties of sHLA, we modified the NIH microcytotoxic test. Furthermore, we determined the concentration of INF-gamma in all sera samples for comparison with the intensity of the cytotoxic test. The comparison of the intensity of cytotoxic test inhibition with the concentration of INF-gamma revealed that high concentrations of this cytokine were associated with stronger inhibition of the cytotoxic test, thus with higher concentrations of sHLA class I molecules in recipient sera. We observed that high concentrations of sHLA class I molecules in recipient sera significantly inhibited cytotoxic reactions, which could contribute to a protective influence of sHLA on renal grafts. On the other hand, the observed increase of INF-gamma concentration might be caused by sHLA themselves, which would produce a detrimental influence on a transplanted organ. Therefore we concluded that the role of sHLA class I molecules in renal graft condition remains ambiguous.

Soluble HLA-I (s-HLA-I) synthesis in systemic lupus erythematosus

Our objective was to study a possible contribution of major histocompatibility complex (MHC) genes to soluble HLA-I synthesis in patients with systemic lupus erythematosus (SLE). Solid-phase enzyme-linked immunoassay (ELISA) was used to measure sHLA-I in the sera of 20 patients with SLE and 76 normal controls with known HLA phenotypes. Serial serum samples ( n=108) from the above group of patients ( n=19) were further investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Soluble HLA-I levels were abnormally higher in patients with SLE than normal controls ( P<0.0002). No complete HLA haplotype has been identified to be correlated with high or low sHLA-I secretion. Only the sera of HLA-A23- or -A24- (splits of HLA-A9) positive individuals were found to contain high sHLA-I concentrations in both populations studied. The difference between sHLA-I of HLA-A24 patients ( n=7) and HLA-A24 normal controls ( n=19) was statistically highly significant ( P<0.0079). The results suggest that HLA-A24 may confer additional risk of more severe disease expression in female patients with SLE. The data imply that SLE patients carrying 39-kDa sHLA-I have increased risk of developing renal disease. A higher prevalence of 35-37 kDa was observed in patients with mild disease. Interestingly, 44-46 kDa was the predominant molecular form of sHLA-I in SLE patients with lymphocytosis with no evidence of organ involvement. Notably, all these variations were not reflected by differences in HLA phenotypes, with the exception of HLA-A24-positive patients, in whom the 44-46-kDa form occurs consistently but not exclusively. In summary, the results show a genetic heterogeneity of SLE with MHC control of the expression of sHLA-I concentrations and possible involvement of disease-associated factors that might potentiate a specific sHLA-I molecule synthesis.

Proteomic analysis of dendritic cell-derived exosomes: a secreted subcellular compartment distinct from apoptotic vesicles

Dendritic cells constitutively secrete a population of small (50-90 nm diameter) Ag-presenting vesicles called exosomes. When sensitized with tumor antigenic peptides, dendritic cells produce exosomes, which stimulate anti-tumor immune responses and the rejection of established tumors in mice. Using a systematic proteomic approach, we establish the first extensive protein map of a particular exosome population; 21 new exosomal proteins were thus identified. Most proteins present in exosomes are related to endocytic compartments. New exosomal residents include cytosolic proteins most likely involved in exosome biogenesis and function, mainly cytoskeleton-related (cofilin, profilin I, and elongation factor 1alpha) and intracellular membrane transport and signaling factors (such as several annexins, rab 7 and 11, rap1B, and syntenin). Importantly, we also identified a novel category of exosomal proteins related to apoptosis: thioredoxin peroxidase II, Alix, 14-3-3, and galectin-3. These findings led us to analyze possible structural relationships between exosomes and microvesicles released by apoptotic cells. We show that although they both represent secreted populations of membrane vesicles relevant to immune responses, exosomes and apoptotic vesicles are biochemically and morphologically distinct. Therefore, in addition to cytokines, dendritic cells produce a specific population of membrane vesicles, exosomes, with unique molecular composition and strong immunostimulating properties.

Soluble HLA class I and Fas ligand molecules in blood components and their role in the immunomodulatory effects of blood transfusions

It has been known for many years that blood transfusions may have immunomodulatory effects, however an ultimate explanation of this phenomenon is lacking. In the present paper we report that the concentrations of soluble HLA class I (sHLA-I) and soluble Fas ligand (sFasL) molecules in supernatants of blood components which contain elevated numbers of residual donor leukocytes, like red blood cells and random-donor platelets, are significantly higher than in other blood components. Elevated amounts of sFasL molecules are also found in some commercial immunoglobulin preparations. sHLA-I and sFasL molecules in blood components and in immunoglobulin preparations are biologically active in vitro as they inhibit mixed lymphocyte responses and cytotoxic T cell activity in allogeneic and autologous combinations and induce apoptosis in Fas-positive cells. If these results are paralleled in vivo the amount of sHLA-I and sFasL molecules should be taken into account in clinical practice in order to select the blood component and the immunoglobulin preparation which could induce the desired immunomodulatory effect in the recipient.

Increased beta2-microglobulin-free HLA class I heavy chain serum levels in the course of immune responses to viral antigens and to mismatched HLA antigens

Besides being present in serum in association with beta2-mu, HLA class I heavy chains are also present in serum as beta2-micro-free moieties. The increase in serum levels of beta2-micro-associated HLA class I heavy chains in conditions associated with an activation of the immune system have prompted us to measure the serum levels of beta2-mu-free HLA class I heavy chains in the course of immune responses to viral antigens and to mismatched histocompatibility antigens. The serum level of beta2-mu-free HLA class I heavy chains, like that of beta2-mu-associated HLA class I heavy chains was significantly increased in patients affected by advanced HIV-1 infection or by chronic hepatitis C (CHC). In the latter group of patients an association was found between a reduction in the beta2-mu-free HLA class I heavy chain serum level and response to therapy with interferon alpha and ribavirin. Moreover, the beta2-mu-free HLA class I heavy chain serum level was increased more than that of beta2-mu-associated HLA class I heavy chains during episodes of liver ischemia following liver transplantation and in the course of acute graft rejection and of acute graft-versus-host-disease (GVHD) after allogeneic bone marrow transplantation (BMT). These results suggest that the serum levels of beta2-mu-free and beta2-mu-associated HLA class I heavy chains are independently regulated. Furthermore, beta2-mu-free HLA class I heavy chain serum level may be a useful marker to monitor response to therapy in CHC patients and the clinical course of liver and bone marrow grafts.

Non-classic sHLA class I in human oocyte culture medium

Soluble human leukocyte antigen (sHLA) class I molecules have been described in all human fluids. These molecules play a significant role in immune function. sHLA has been shown to produce tolerance and to induce apoptosis in cytotoxic alloreactive T cells. They are also present in the supernatant of many cultured cells. Similarly, non-classic HLA class I antigens in soluble form are present in human fluids. Among these, HLA-G is the most important because of its location in fetal tissue that suggests maternal immunological tolerance of the fetal semiallograft. In our present study we show that using two monoclonal antibodies, w6/32 and TP25.99, in the enzyme-linked immunosorbent assay allows the detection of non-classic sHLA class I molecules in the medium from human embryo cultures. The sample were collected from oocytes cultures. Oocyte donors were 11 women attending the in vitro fertilization program. The results showed a significant association (chi2 = 9.66, p = 0.002) between sHLA antigens and the oocyte cleavage rate measured 48 h after fertilization.

Anti-HLA antibodies interfere in the detection of soluble HLA class I molecules

Heart transplant rejection is routinely defined by histological evaluation of endomyocardial biopsies (EMB). As elevated levels of donor derived sHLA (dsHLA) can be detected in the serum of transplanted patients just before or during rejection, quantification of donor specific soluble counterparts of HLA Class I (sHLA-I) in the serum of the recipient may be a new way for non-invasive monitoring of graft rejection. However, not all patients show an increase of dsHLA at time of rejection. A reason for this might be that anti-donor-HLA antibodies, which are formed by the patient, form complexes with donor sHLA-I molecules. This masking or blocking of sHLA-I binding sites might cause false-negative results of tests detecting donor specific sHLA. Using HLA-antigen specific ELISA tests we could demonstrate that most anti-HLA antibodies block the detection of sHLA antigens in plasma, even in high dilutions of the antibody when the antibodies were not detectable in a CDC test. In general, HLA-antigen specific antibodies block the detection of sHLA molecules, while broadly-reactive antibodies, recognizing another epitope on the molecule, do not. The implication of these findings is that more than one dsHLA allotype within one patient should be tested to monitor graft rejection. In addition, sHLA monitoring must be combined with an HLA-antibody screening.

Soluble HLA Class I, HLA Class II, and Fas Ligand in Blood Components: A Possible Key to Explain the Immunomodulatory Effects of Allogeneic Blood Transfusions

The immunomodulatory effect of allogeneic blood transfusions (ABT) has been known for many years. However, a complete understanding of the effects of ABT on the recipient’s immune system has remained elusive. Soluble HLA class I (sHLA-I), HLA class II (sHLA-II), and Fas ligand (sFasL) molecules may play immunoregulatory roles. We determined by double-determinant immunoenzymatic assay (DDIA) sHLA-I, sHLA-II, and sFasL concentrations in different blood components. sHLA-I and sFasL levels in red blood cells (RBCs) stored for up to 30 days and in random-donor platelets are significantly (P < .001) higher than in other blood components and their amount is proportionate to the number of residual donor leukocytes and to the length of storage. Blood components with high sHLA-I and sFasL levels play immunoregulatory roles in vitro as in allogeneic mixed lymphocyte responses (MLR) and antigen-specific cytotoxic T-cell (CTL) activity, and induce apoptosis in Fas-positive cells. These data suggest that soluble molecules in blood components are functional. If these results are paralleled in vivo, they should be taken into account in transfusion practice. Blood components that can cause immunosuppression should be chosen to induce transplantation tolerance, whereas blood components that lack immunosuppressive effects should be preferred to reduce the risk of postoperative complications and cancer recurrence.

Soluble HLA in human body fluids

There is a growing body of information about the soluble forms of HLA in serum but there are only a few reports discussing sHLA in other body fluids. We quantitated sHLA-I and sHLA-II concentrations in sweat, saliva and tear samples from five normal individuals with known HLA-phenotypes. We also studied sweat samples from an additional 12 normal nonphenotyped subjects, as well as in CSF of 20 subjects with different illnesses, using solid phase enzyme linked immunoassay. Sweat, saliva and tears from normal subjects were found to contain very low or nondetectable amounts of sHLA-I. In contrast, sHLA-II molecules were found in each of these body fluids, although, with considerable variation between individuals. The presence of sHLA-II in saliva was further confirmed by Western-blotting. It was observed that sHLA-II having molecular mass of 43,900 and 18,100 daltons was comparable with that found in serum from normal individuals. In addition, no association of sHLA-II levels with allospecificities in either body fluid or in serum was apparent. The results of CSF sHLA concentrations in different diseases were as follows: (1) High CSF SHLA-I levels were measured during viral encephylitis (n = 3), while none of these patients contained sHLA-II in CSF; (2) The levels of sHLA-II, but not sHLA-I were elevated in CSF of patients during seizure (n = 6) and of patients with neonatal hepatitis (1 of 2) or with connective tissue disease accompanied with viral infection (n = 2); (3) No CSF sHLA-I or sHLA-II could be detected at polyneuropathy (n = 2), or in patients with syphilis (n = 3), or leukemia (n = 2) with evidence of neurologic involvement of central nervous system. Taken together, it may be concluded that the presence of sHLA in several body fluids is physiologically normal. It appears that sHLA-II is the predominant class of HLA molecules present in different body fluids. We propose that the system responsible for sHLA-II production in various body fluids must involve different mechanisms than those responsible for sHLA-I synthesis in serum.

Beta2-micro-free HLA class I heavy chain levels in sera of healthy individuals. Lack of association with beta2-micro-associated HLA class I heavy chain levels and HLA phenotype

We have applied a double-determinant immune assay (DDIA) to measure soluble beta2-microglobulin (beta2-micro)-free HLA class I heavy chains in serum. The mean concentration of beta2-micro-free HLA class I heavy chains in serum from 120 healthy subjects was 0.21+/-0.24 microg/ml. The individual serum levels of beta2-micro-free HLA class I heavy chains had a wide distribution, did not seem to be related with HLA phenotype, were stable over time and did not change with age. The serum levels of soluble beta2-micro-free HLA class I heavy chains did not correlate with those of soluble beta2-micro-associated HLA class I heavy chains, suggesting that their release is independently regulated. Three forms of soluble beta2-micro-free HLA class I heavy chains, with apparent molecular masses of 44, 39 and 37-35 kD, respectively, circulate in human serum. These results provide a useful background to assess the serum level of soluble beta2-micro-free HLA class I heavy chains in pathological conditions and to evaluate their putative immunoregulatory function.

Soluble HLA Class I, HLA Class II, and Fas Ligand in Blood Components: A Possible Key to Explain the Immunomodulatory Effects of Allogeneic Blood Transfusions

The immunomodulatory effect of allogeneic blood transfusions (ABT) has been known for many years. However, a complete understanding of the effects of ABT on the recipient’s immune system has remained elusive. Soluble HLA class I (sHLA-I), HLA class II (sHLA-II), and Fas ligand (sFasL) molecules may play immunoregulatory roles. We determined by double-determinant immunoenzymatic assay (DDIA) sHLA-I, sHLA-II, and sFasL concentrations in different blood components. sHLA-I and sFasL levels in red blood cells (RBCs) stored for up to 30 days and in random-donor platelets are significantly (P &lt; .001) higher than in other blood components and their amount is proportionate to the number of residual donor leukocytes and to the length of storage. Blood components with high sHLA-I and sFasL levels play immunoregulatory roles in vitro as in allogeneic mixed lymphocyte responses (MLR) and antigen-specific cytotoxic T-cell (CTL) activity, and induce apoptosis in Fas-positive cells. These data suggest that soluble molecules in blood components are functional. If these results are paralleled in vivo, they should be taken into account in transfusion practice. Blood components that can cause immunosuppression should be chosen to induce transplantation tolerance, whereas blood components that lack immunosuppressive effects should be preferred to reduce the risk of postoperative complications and cancer recurrence.

Simultaneous heart and kidney transplantation as treatment for end-stage heart and kidney failure

BACKGROUND

The aim of the present analysis was to define the role of simultaneous heart and kidney transplantation (HNTX) using organs from the same donor by evaluation of clinical strategy and achieved outcome compared with a reference group of concurrently single heart transplant (HTX) and kidney transplant (NTX) recipients. Compared with other organ combinations (pancreas-kidney, heart-lung), HNTX has been performed infrequently and is reported mainly as case records in the literature. Because of expansion of recipient selection criteria for HTX and NTX, the number of patients requiring simultaneous replacement of both organs is increasing.

METHODS

Six HNTX recipients, three of them suffering from long-standing type I diabetes, received transplants between September 1990 and March 1996 and were analyzed in terms of clinical and immunological demographics and outcome. They were compared with 379 HTX and 769 NTX recipients operated upon within this period.

RESULTS

Survival for HNTX is 100% with a mean follow-up of 32.7+/-21.1 months. Cold ischemic time of the kidney was significantly shorter for HNTX than for NTX (6.5+/-1.0 hr vs. 22.1+/-6.8 hr, P<0.005). Although HNTX patients received HLA-unmatched grafts, no rejection of the kidney has been observed to date. There was no difference for rejection of the heart in HNTX compared to HTX recipients.

CONCLUSIONS

Satisfying results are obtained by HNTX and justify the use of two organs for one recipient. The favorable immunological behavior of the kidney despite use of HLA-unmatched grafts is most probably explained by higher immunosuppression and short cold ischemic time, although a combination effect cannot be excluded.

Serologic allogeneic chimerism

BACKGROUND

At least some transplanted livers secrete soluble human leukocyte antigens (sHLA) of donor phenotype into the body fluids of recipients. The individuals in whom this phenomenon occurs are by definition serologic allogeneic chimeras. Because an allogeneic transplanted liver may induce tolerance to itself and other organs in animals of the donor strain, and because maintenance of a soluble antigen in the circulation of any animal in sufficient quantity for a sufficient period generally leads to tolerance, this phenomenon may be biologically important. This study was performed to determine how common this phenomenon is and whether it occurs after transplantation of organs other than the liver.

METHODS

We studied 445 serum samples obtained from transplant recipients (liver, n=12; kidney, n=18; and heart, n=8) before and at various intervals after transplantation. All patients studied had allografts that had functioned for more than 1 year. We used an enzyme-linked immunosorbent assay to quantitate sHLA-A2 and sHLA-A1/A3/A11 (as a cross-reacting group). Donor and recipient combinations were selected in which measurable allotypes in donors were not present in recipients. In some instances, an additional allotype was present in a recipient but not in a donor.

RESULTS

All liver transplant recipients had detectable donor sHLA in their serum samples after transplantation. In 72% of kidney and 50% of heart transplant recipients, donor sHLA was found persistently in serum samples obtained after transplantation. Interestingly, all heart transplant recipients of HLA-A3, but none of HLA-A2, had detectable donor sHLA in their serum samples, a finding that may be due to technical reasons. High and stable serum concentrations of donor sHLA characterize long-term stable allograft function.

CONCLUSIONS

Donor sHLA is produced by all transplanted livers, most transplanted kidneys, and at least half of (but probably more) transplanted hearts. The hypothesis that donor sHLA may be tolerogenic to liver transplants can be expanded to include kidney and heart transplants.

Serum soluble human leucocyte antigen class I in paediatric liver transplantation with live, related donors

Serum soluble human leucocyte antigen (HLA) class-I is a useful marker for predicting immunological events in organ transplantation. In cadaver liver transplant cases it is especially the case that high amounts of soluble HLA-I are excreted from the grafts. In Japan, almost all liver transplants have been performed from living parent donors to their children. Therefore, it is interesting to know how soluble HLA-I changes in relation to clinical course. As part of this study we first examined serum concentrations of soluble HLA-I in 33 paediatric patients using enzyme-linked immunosorbent assay. Soluble HLA-I is composed of three different sized molecules (45, 39 and 34-36 kDa); then the change of distribution of these three molecules was demonstrated by Western blot analysis. When donor and recipient have different soluble HLA-I band patterns, the origin of the antigen can be assumed by this method. We found that in a comparison between pre- and post-transplants, the six out of eight (75%) patients that suffered episodes of acute rejection showed a significant elevation of soluble HLA-I, and all patients with infectious episodes had an elevated soluble HLA-I. Meanwhile, 10 out of 22 (45%) patients without any clinical complications still showed increased soluble HLA-I. The Western blot analysis showed that the soluble HLA-I molecules were considerably derived from the grafted liver, from one week to 24 months after grafting. In acute rejection, the band signals of donor origin were significantly increased. These signals were attenuated after immunosuppressive therapy. The grafted liver appears to contribute to the increase of soluble HLA-I following liver transplantation, and this increase is greater with the effects of the host immune system.

Soluble HLA class I antigens in patients with type I diabetes and their family members

Our objective was to study a possible contribution of MHC genes to S-HLA-I secretion in patients with Type I diabetes. Quantitatively, we used a highly sensitive enzyme-linked immunoassay to measure S-HLA-I in the serum of a total of 39 patients with Type I diabetes, as well as 36 kinships of 12 diabetic patients and 82 normal individuals with known HLA-phenotypes. S-HLA-I levels were abnormally elevated in patients or their non-diabetic relatives compared to normal controls (p < 0.0009). No complete HLA-haplotype had been identified to be correlated with high or low S-HLA-I secretion. Only the HLA-A23 or A24 (splits of HLA-A9) positive individuals sera were found to contain high S-HLA-I concentrations in all populations studied. The difference in S-HLA-I levels of HLA-A24 patients (n = 4) or their HLA-A24 positive non-diabetic relatives (n = 10) to the group of HLA-A24 normal controls (n = 15) was statistically highly significant (p < 0.0005 and p < 0.0009, respectively). The results suggests that HLA-A24 may confer additional independent risk for the disease expression in male children but not in female siblings. Nevertheless, the data implies that the patients or their non-diabetic relatives carrying the HLA-A24 have increased risk of developing ICA associated with high S-HLA-I levels compared to HLA-A24 negative probands or their kinships with low levels of S-HLA-I. This effect occurred irrespective to other diabetes related HLA-DR alleles. In summary, the results show a pronounced genetic heterogeneity of Type I diabetes with MHC control of the expression of S-HLA-I and possible involvement of hormonal factors that might potentiate a specific synthesis of S-HLA-I. The findings have implications for identifying individuals with a possible risk for developing the disease.

Soluble histocompatibility class I antigens and beta 2-microglobulin in pregnant females and cord blood samples

Pregnancy can be considered a successful transplantation of allogeneic paternal tissue to the mother. Soluble HLA class I serum levels have been found to increase during solid organ rejection episodes and during graft-versus-host disease after bone marrow transplantation. We wished to determine whether significant changes in sHLA class I and beta 2-microglobulin light chain levels occurred during pregnancy, because these may reflect adaptive changes permitting the acceptance of the fetal graft. Serum samples were obtained from women at different stages of pregnancy and in the postpartum period. Cord blood samples and serum samples from nonpregnant female and male controls living in the same geographic area in Southern Chile were also studied. The levels of sHLA class I heterodimers were determined by an ELISA sandwich technique; beta 2-microglobulin levels were measured by MEIA IMX-Abbott. There was a significant elevation of sHLA class I levels in the first 2 trimesters of pregnancy, followed by a significant drop below normal levels at the end of pregnancy, with normalization in the post-partum period. beta 2-microglobulin levels did not change significantly during pregnancy and did not correlate with sHLA class I levels. In cord blood samples, sHLA class I levels were lower and beta 2-microglobulin levels higher than those of adult controls and of mothers at the time of delivery. The variations in sHLA class I levels during pregnancy may reflect or contribute to immunoregulatory events related to the acceptance of the fetal graft.

Biochemical and immunological evaluation of donor-specific soluble HLA in the circulation of liver transplant recipients

MHC antigens, normally expressed as integral membrane proteins, are also present in soluble form in the peripheral circulation. These soluble human leukocyte antigens (sHLA) are found at elevated levels in patients with a variety of infections as well as in organ transplant recipients. In liver transplant recipients, however, most of the circulating sHLA are of donor phenotype, especially during the early posttransplant period. Here we report the purification and characterization of sHLA of both recipient and donor origin from liver transplant recipients. It was observed that sHLA consisted of four major polypeptides having molecular mass of 44, 41, 35-37, and 12 kD complexed with IgM and IgG antibodies. Further analysis revealed that these immunoglobulins contained anti-HLA antibodies. Analysis of the affinity-purified materials by a number of approaches failed to detect any other fragment(s) of HLA class I heavy chain polypeptides smaller than 12 kD. No significant difference was observed in the biochemical nature of the sHLA of donor and recipient origin and they were similar to those found in normal individuals. Affinity-purified HLA-A3 inhibited the cytolytic activity of an HLA-A3-specific CD8+ T cell line, whereas, purified sHLA-A2 failed to inhibit anti-HLA-A3 CTL activity. Further, the proliferation of the T cell line was not inhibited by sHLA-A3. Thus, the inhibitory activity shown by sHLA was antigen-specific and directed against a functional subset of T lymphocytes. These results support the notion that sHLA may play an important regulatory role in the immune response to allograft in humans.

Allogeneic lymphocyte chimerism after clinical lung transplantation

Donor lungs contain large amounts of passenger leukocytes which are transferred to the recipient by organ transplantation. In this study we have analysed the fate of these cells and have studied the populations of donor leucocytes detectable in the blood circulation of ten lung transplanted patients during the first postoperative weeks. To this aim we have applied immunocytological as well as flow cytometric analyses using monoclonal antibodies against polymorphic HLA class I antigens that differed between donor and recipient as well as antibodies against cell differentiation markers. The results demonstrate that donor cells can be detected in the circulation of all lung transplanted patients but there is a considerable interindividual variability between 0.9% and 17.5% (mean 5.1%) on postoperative day 3. Cells were usually detectable for 2-4 weeks and had disappeared in all patients after 1 month. The circulating donor cells consisted exclusively of lymphocytes. T cells were the predominant population, most of which seemed to be CD45R0+, but B and NK (natural killer) cells were also present. Probably due to the small numbers of patients studied no correlation between clinical parameters and the extent of donor lymphocyte persistence; there were no clinical graft-versus-host reactions. The findings demonstrate the regular existence of a transient (macro)chimerism due to passenger lymphocytes in the early phase after lung transplantation. The immunological function and the relation between this phenomenon and the long-term microchimerism which frequently develops after solid organ transplantation remain unclear.

Prospects for induction of tolerance in renal transplantation

Immunological tolerance is the ultimate goal of transplantation immunobiology. Current therapies involve nonspecific immunosuppression with concomitant risks for infection, malignancy, and drug-specific side effects. By inducing specific immune unresponsiveness to the graft it should be possible to maintain transplants without the need for chronic drug administration and without the risk of nonspecific immunosuppression. This review highlights recent progress in the understanding of immunological tolerance, with special attention to the long-term prospects for successful induction of tolerance in renal transplant patients.

Quantification of serum-soluble HLA class I antigens in patients with gastric cancer

The amount of sHLA-I in serum was examined in 74 patients with gastric cancer and 15 normal healthy controls. For mAbs, W6/32 specific for HLA-A, -B, -C, and biotin IOT2 specific for HLA class I associated with beta 2 microglobulin, were used to determine the values of sHLA-I using an ELISA. The patients in stage-IV gastric cancer showed lower values of sHLA-I (445.4 +/- 247.1 ng/ml) than those in stage I (725.9 +/- 575.8 ng/ml), stage II (752.8 +/- 255.0 ng/ml), and normal controls (868.9 +/- 715.0 ng/ml) (P < 0.05). In analysis of the patients with HLA-A24, the allele that has been reported to secrete more sHLA-I than other alleles, the results were nearly the same. These results suggest that the secretion of sHLA-I is low in patients with very advanced cancer. However, there was no correlation between the sHLA-I level and the metastasis or prognosis in longitudinal studies in 11 patients.

HLA class-I-soluble antigen serum levels in liver transplantation. A predictor marker of acute rejection

The serum levels of sHLA-I have been determined in 16 patients following liver transplantation. sHLA-I levels did not show remarkable variations in six patients without evidence of transplant-related complications. sHLA-I levels strongly increased in 10 patients undergoing acute rejection episodes. In these patients, an average 20% daily increase of sHLA-I levels was detected on the 6 days preceding and on the 2 days following the rejection episode. A fast decrease of sHLA-I levels was observed in seven patients following treatment of acute rejection with anti-CD3 mAb. The serum level of sHLA-I antigens positively correlated with ALT serum level and inversely correlated with PT. The determination of sHLA-I in serum may therefore be proposed as a useful marker in the monitoring of patients following liver transplantation. The increase of sHLA-I antigens may predict the onset of acute rejection whereas their decrease may be related to a good response of acute rejection to immunosuppressive treatment.