Activation markers on peripheral blood T cells from patients with active or inactive systemic lupus erythematosus. Correlation with proliferative responses and production of IL-2

CD38 Correlates with an Immunosuppressive Treg Phenotype in Lupus-Prone Mice

CD38 is a transmembrane glycoprotein expressed by T-cells. It has been reported that patients with systemic lupus erythematosus (SLE) showed increased CD38⁺CD25⁺ T-cells correlating with immune activation and clinical signs. Contrariwise, CD38 deficiency in murine models has shown enhanced autoimmunity development. Recent studies have suggested that CD38⁺ regulatory T-cells are more suppressive than CD38⁻ regulatory T-cells. Thus, we have suggested that CD38 overexpression in SLE patients could play a role in regulating immune activation cells instead of enhancing it. This study found a correlation between CD38 with FoxP3 expression and immunosuppressive molecules (CD69, IL-10, CTLA-4, and PD-1) in T-cells from lupus-prone mice (B6.MRL-Fas^lpr/J). Additionally, B6.MRL-Fas^lpr/J mice showed a decreased proportion of CD38⁺ Treg cells regarding wild-type mice (WT). Furthermore, Regulatory T-Cells (Treg cells) from CD38-/- mice showed impairment in expressing immunosuppressive molecules and proliferation after stimulation through the T-cell receptor (TCR). Finally, we demonstrated an increased ratio of IFN-γ/IL-10 secretion in CD38-/- splenocytes stimulated with anti-CD3 compared with the WT. Altogether, our data suggest that CD38 represents an element in maintaining activated and proliferative Treg cells. Consequently, CD38 could have a crucial role in immune tolerance, preventing SLE development through Treg cells.

The CD38/NAD/SIRTUIN1/EZH2 Axis Mitigates Cytotoxic CD8 T Cell Function and Identifies Patients with SLE Prone to Infections

Patients with systemic lupus erythematosus (SLE) suffer frequent infections that account for significant morbidity and mortality. T cell cytotoxic responses are decreased in patients with SLE, yet the responsible molecular events are largely unknown. We find an expanded CD8CD38^high T cell subset in a sub-group of patients with increased rates of infections. CD8CD38^high T cells from healthy subjects and patients with SLE display decreased cytotoxic capacity, degranulation, and expression of granzymes A and B and perforin. The key cytotoxicity-related transcription factors T-bet, RUNX3, and EOMES are decreased in CD8CD38^high T cells. CD38 leads to increased acetylated EZH2 through inhibition of the deacetylase Sirtuin1. Acetylated EZH2 represses RUNX3 expression, whereas inhibition of EZH2 restores CD8 T cell cytotoxic responses. We propose that high levels of CD38 lead to decreased CD8 T cell-mediated cytotoxicity and increased propensity to infections in patients with SLE, a process that can be reversed pharmacologically.

Katsuyama et al. find that an expanded CD8CD38^high T cell population in SLE patients is linked to infections. CD8CD38^high T cells display decreased cytotoxic capacity by suppressing the expression of related molecules through an NAD⁺/Sirtuin1/EZH2 pathway. EZH2 inhibitors increase cytotoxicity offering a means to mitigate infection rates in SLE.

Immunophenotyping reveals distinct subgroups of lupus patients based on their activated T cell subsets

OBJECTIVE

This study performed an integrated analysis of the cellular and transcriptional differences in peripheral immune cells between patients with Systemic Lupus Erythematosus (SLE) and healthy controls (HC).

METHODS

Peripheral blood was analyzed using standardized flow cytometry panels. Transcriptional analysis of CD4+ T cells was performed by microarrays and Nanostring assays.

RESULTS

SLE CD4+ T cells showed an increased expression of oxidative phosphorylation and immunoregulatory genes. SLE patients presented higher frequencies of activated CD38+HLA-DR+ T cells than HC. Hierarchical clustering identified a group of SLE patients among which African Americans were overrepresented, with highly activated T cells, and higher frequencies of Th1, Tfh, and plasmablast cells. T cell activation was positively correlated with metabolic gene expression in SLE patients but not in HC.

CONCLUSIONS

SLE subjects presenting with activated T cells and a hyperactive metabolic signature may represent an opportunity to correct aberrant immune activation through targeted metabolic inhibitors.

Increased CD38 expression in T cells and circulating anti-CD38 IgG autoantibodies differentially correlate with distinct cytokine profiles and disease activity in systemic lupus erythematosus patients

CD38 is a multifunctional protein possessing ADP-ribosyl cyclase activity responsible for both the synthesis and the degradation of several Ca(2+)-mobilizing second messengers. In mammals, CD38 also functions as a receptor. In this study CD38 expression in CD4(+), CD8(+), or CD25(+) T cells was significantly higher in systemic lupus erythematosus (SLE) patients than in Normal controls. Increased CD38 expression in SLE T cells correlated with plasma levels of Th2 (IL-4, IL-10, IL-13) and Th1 (IL-1β, IL-12, IFN-γ, TNF-α) cytokines, and was more prevalent in clinically active SLE patients than in Normal controls. In contrast, elevated anti-CD38 IgG autoantibodies were more frequent in clinically quiescent SLE patients (SLEDAI=0) than in Normal controls, and correlated with moderate increased plasma levels of IL-10 and IFN-γ. However, clinically active SLE patients were mainly discriminated from quiescent SLE patients by increased levels of IL-10 and anti-dsDNA antibodies, with odds ratios (ORs) of 3.7 and 4.8, respectively. Increased frequency of anti-CD38 autoantibodies showed an inverse relationship with clinical activity (OR=0.43), and in particular with the frequency of anti-dsDNA autoantibodies (OR=0.21). Increased cell death occurred in CD38(+) Jurkat T cells treated with anti-CD38(+) SLE plasmas, and not in these cells treated with anti-CD38(-) SLE plasmas, or Normal plasmas. This effect did not occur in CD38-negative Jurkat T cells, suggesting that it could be attributed to anti-CD38 autoantibodies. These results support the hypothesis that anti-CD38 IgG autoantibodies or their associated plasma factors may dampen immune activation by affecting the viability of CD38(+) effector T cells and may provide protection from certain clinical SLE features.

Increased association of CD38 with lipid rafts in T cells from patients with systemic lupus erythematosus and in activated normal T cells

In this study we have determined whether there is a relationship between CD38 expression on T cells, its distribution in different membrane microdomains, and T cell activation in SLE patients. The data show that CD38 expression is augmented in ex vivo CD3+, CD4+, CD8+, and CD25+ SLE T cells, which correlates with its increased insolubility in Brij 98 detergent, and its translocation into lipid rafts. Moreover, SLE T cells show an altered CD4:CD8 ratio, which is due to a decreased proportion of CD4+ T cells and a concomitant increase in the proportion of CD8+ T cells. These data are consistent with the increased CD38 expression and lipid raft formation, and the significant reduction in the CD4:CD8 ratio observed in mitogen-stimulated normal T cells as compared with that in ex vivo untouched normal T cells. Increased expression of CD38 in floating rafts from SLE T cells, or from activated normal T cells may modulate TCR signaling by providing or sequestering signaling molecules to the engaged TCR.

Increase of activated T-cells and up-regulation of Smad7 without elevation of TGF-beta expression in tonsils from patients with pustulosis palmaris et plantaris

Pustulosis palmaris et plantaris (PPP) is known to be a skin disease related to tonsillitis, because the pustulosis often become exacerbated during acute tonsillitis and disappears after tonsillectomy. However, etiology of PPP remains unclear. In this study, we investigated the activation of tonsillar T-cell from PPP patients. Furthermore, we analyzed expressions of cytotoxic T-lymphocyte antigen-4 (CTLA4) that is a co-stimulatory molecule for inhibition of T-cell activation and of Smad7 that is a regulatory factor of TGF-beta intracellular signaling. For 47 Japanese patients with PPP who had tonsillectomy, the skin lesion was improved in 87% of PPP patient at 12 months after tonsillectomy. In quantitative immunohistologic analysis, T-cell nodules on tonsillar tissues from PPP patients were more expanded than those from the patients with obstructive sleep apnea syndrome (OSAS) (P = 0.015), and there was a positive correlation between the enlargement and clinical improvement (r = 0.422, P = 0.021). Flow cytometric analysis showed that the numbers of CD4+CD25+ and CD4+CD29+ cells in tonsils from PPP patients increased significantly compared to those from OSAS patients (P = 0.017, P = 0.016, respectively). Using reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analyses with CD3+ tonsillar lymphocytes, we found that both expressions of Smad7 mRNA and protein were enhanced in PPP patients compared with OSAS patients (P = 0.03, P = 0.02, respectively), but expression of TGF-beta mRNA was not different between 2 groups. Although mRNA expression of CTLA4 was reduced in PPP patients compared with OSAS patients (P = 0.04), the CTLA4 surface protein expression was not different between 2 groups. These data suggest that helper T-cells are frequently activated in tonsils from PPP patients, and this activation may be related to unresponsiveness of TGF-beta1 by overexpression of Smad7. Such hyper-activation of T-cell may increase the risk of elicitation of self-reactive T-cell, being associated with pathogenesis of PPP.

The role of very late antigen-1 in immune-mediated inflammation

The alpha1beta1 integrin, also known as "very late antigen" (VLA)-1, is normally expressed on mesenchymal cells, some epithelial cells, activated T cells, and macrophages, and interacts, via the I-domain of the extracellular domain of the alpha1 subunit, with collagen molecules in the extracellular matrix (ECM). By "outside-in" transmembranal signaling to the interior of the cell, it mediates adhesion, migration, proliferation, remodeling of the ECM, and cytokine secretion by endothelial cells, mesangial cells, fibroblasts, and immunocytes. Importantly, its expressions and functions are enhanced by inflammatory cytokines including interferon (IFN)gamma and tumor necrosis factor (TNF)alpha, thus augmenting angiogenesis and fibrosis linked, in particular, to inflammation. Moreover, within the immune system, VLA-1 marks effector memory CD4+ and CD8+ T cells that are retained in extralymphatic tissues by interactions of the integrin with collagen and produce high levels of IFNgamma. Thus, immune-mediated inflammation in vivo is inhibited by blockade of the VLA-1-collagen interaction in experimental animal models of arthritis, colitis, nephritis, and graft versus host disease (GVHD), suggesting that inhibiting the interaction of the alpha1 I-domain with its ligands or modulating "outside-in" signaling by VLA-1 would be a useful approach in the human diseases simulated by these experimental models.

A pilot study of the use of 2-[18F]-fluoro-2-deoxy-D-glucose-positron emission tomography to assess the distribution of activated lymphocytes in patients with systemic lupus erythematosus

OBJECTIVE

The 2-[(18)F]-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) technique provides information on uptake and metabolism of glucose in various tissues. Compared with resting cells, activated lymphocytes take up radioactively labeled glucose analog at a higher rate, which makes it possible to identify lymphoid organs with higher concentrations of activated lymphocytes. This study was undertaken to compare the pattern of PET images and quantitative FDG uptake in lymphoid organs of patients with active systemic lupus erythematosus (SLE) versus patients with inactive SLE and to correlate these findings with peripheral blood lymphocyte phenotypes.

METHODS

Ten patients with active SLE and 9 patients with inactive SLE were studied. FDG-PET images were obtained from the inguinal region to above the ear, starting at 60 minutes after injection of FDG. Standardized uptake values using lean body mass were determined over areas of interest.

RESULTS

Both patients with active lupus and those with inactive lupus had increased FDG uptake in lymph nodes when compared with healthy volunteers, and there was no statistically significant difference between the 2 groups of lupus patients. Thymic uptake was demonstrated in 5 of 10 patients with active lupus compared with 0 of 9 patients with inactive disease. Three of the 5 patients with active SLE who were over 29 years of age had thymic uptake. Of the activation markers tested, only the CD3/CD71 population of cells was significantly different between the patient groups, with an increased percentage in the active disease group (P = 0.0247).

CONCLUSION

Increased FDG uptake in lymph nodes of both patients with active SLE and patients with inactive SLE suggests that metabolic, and probably immunologic, activity is enhanced not only in active, but also in clinically quiescent, disease. The increased thymic uptake observed only in patients with active disease suggests that the thymus plays an important role during periods of disease activity.

Differential B- and T-cell activation in Wegener's granulomatosis

BACKGROUND

Autoimmune mechanisms are postulated to play a role in the development and progression of Wegener's granulomatosis (WG), a form of systemic, idiopathic necrotizing vasculitis.

OBJECTIVE

We investigated the relation between lymphocyte activation and disease activity in patients with WG.

METHODS

B- and T-lymphocyte activation was studied by cytometric assessment of the expression of the activation markers CD38 on B cells and CD25 and HLA-DR on CD4(+) and CD8(+) T-cell subsets, respectively. Activation at the cellular level was related to serum levels of antineutrophil cytoplasmic antibodies and soluble IL-2 receptor, which can be regarded as soluble activation markers of B and T cells.

RESULTS

Percentages of CD38(bright) activated B cells were higher in patients with active WG than in patients experiencing disease remission (P <.05) or in healthy control subjects (P <.05). Percentages of activated CD4(+) and CD8(+) T cells were higher in patients with active WG (CD4 subset, P <.0001; CD8 subset, P <.005) than in healthy individuals. An increased percentage of activated T cells of both subsets was also seen in patients whose condition was in remission, as compared with healthy control subjects (CD4 subset, P <.0005; CD8 subset, P <. 001). Lymphocyte activation at the cellular level did not correlate with plasma levels of antineutrophil cytoplasmic antibodies or soluble IL-2 receptor.

CONCLUSION

In WG, B-cell activation is related to active disease, whereas T-cell activation persists during remission of the disease, which points to an intrinsic disordered immune system in this disease.

Functional activation of lymphocyte CD44 in peripheral blood is a marker of autoimmune disease activity

Interactions between complementary receptors on leukocytes and endothelial cells play a central role in regulating extravasation from the blood and thereby affect both normal and pathologic inflammatory responses. CD44 on lymphocytes that has been "activated" to bind its principal ligand hyaluronate (HA) on endothelium can mediate the primary adhesion (rolling) of lymphocytes to vascular endothelial cells under conditions of physiologic shear stress, and this interaction is used for activated T cell extravasation into an inflamed site in vivo in mice (DeGrendele, H.C., P. Estess, L.J. Picker, and M.H. Siegelman. 1996. J. Exp. Med. 183:1119-1130. DeGrendele, H.D., P. Estess, and M.H. Siegelman. 1997. Science. 278:672-675. DeGrendele, H.C., P. Estess, and M.H. Siegelman. 1997. J. Immunol. 159: 2549-2553). Here, we have investigated the role of lymphocyte-borne-activated CD44 in the human and show that CD44-dependent primary adhesion is induced in human peripheral blood T cells through T cell receptor triggering. In addition, lymphocytes capable of CD44/HA-dependent rolling interactions can be found resident within inflamed tonsils. In analysis of peripheral bloods of patients from a pediatric rheumatology clinic, examining systemic lupus erythematosus, and a group of chronic arthropathies, expression of CD44-dependent primary adhesion strongly correlates with concurrent symptomatic disease, with 85% of samples from clinically active patients showing elevated levels of rolling activity (compared with only 4% of inactive patients). These rolling interactions are predominantly mediated by T cells. The results suggest that circulating T lymphocytes bearing activated CD44 are elevated under conditions of chronic inflammation and that these may represent a pathogenically important subpopulation of activated circulating cells that may provide a reliable marker for autoimmune or chronic inflammatory disease activity.

Participation of the CD69 antigen in the T-cell activation process of patients with systemic lupus erythematosus

Accumulating evidence has implicated T cells in the pathogenesis of systemic lupus erythematosus (SLE). The CD69 antigen is an integral membrane protein rapidly induced on the surface of activated lymphocytes. We obtained CD4+ and CD8+ T cells from normal subjects and patients with SLE. The percentage of CD69 expression in freshly isolated cells and after in-vitro incubation with mitogens was quantified by three-colour immunofluorescent staining. Expression of this protein was increased in both CD4+ and CD8+ T-cell subsets from SLE patients when compared with normal cells, although the difference was significant only in the CD8+ T-cell subset (P = 0.05). Cellular activation increased CD69 expression. When stimulated with anti-CD2/CD2R or phytohaemagglutinin (PHA), the percentage and absolute numbers of CD69+ cells were lower in patients than in controls. Addition of anti-interleukin (IL)-10 monoclonal antibody (MoAb) increased the percentage of in-vitro CD69 expression in SLE cells. These results suggest that the peripheral blood lymphocytes from patients with SLE have an intrinsic defect that alters their activation process, including the expression of CD69, and might explain some of the T immunoregulatory abnormalities observed in these patients.

Interleukin-2 and systemic lupus erythematosus--fifteen years later

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.

T cell receptor clonotypes in skin lesions from patients with systemic lupus erythematosus

Systemic lupus erythematosus is an autoimmune disease characterized by the presence of autoantibodies and by lymphocytic infiltration into lesions at several sites such as skin, kidney, and other organs. Immunohistologic studies have clarified that the majority of lymphocytes in the skin are CD4+ alphabeta T cells. In the present work, to clarify the pathologic role of T cells in the skin of systemic lupus erythematosus patients, we analyzed T cell receptor (TCR) clonotypes of T cells infiltrating into skin lesions. TCR Vbeta gene transcripts from T cells from discoid lesions of the skin and peripheral blood lymphocytes of four systemic lupus erythematosus patients were amplified by reverse transcriptase polymerase chain reaction. Southern blot analysis of polymerase chain reaction product demonstrated the heterogeneous TCR Vbeta repertoire of T cells in the skin of systemic lupus erythematosus. Single-strand conformation polymorphism analysis showed several distinct bands for smears of most TCR Vbeta genes from T cells infiltrating the skin, whereas smears with few bands were found for all TCR Vbeta genes from peripheral blood lymphocytes of the same patients. The number of bands encoding each TCR Vbeta gene from the skin was significantly higher compared with peripheral blood lymphocytes. Sequencing analysis showed a Leucine-X-Glycine amino acid motif at position 96-98 in the CDR3 region at the frequency of 23-24% in skin-accumulated T cells from two patients, whereas the frequency of this motif in peripheral T cells was only 0-3%, indicating limited T cell epitopes. In conclusion, T cells infiltrating into the skin of systemic lupus erythematosus patients might recognize restricted T cell epitopes on autoantigens and trigger the autoimmune reaction in skin lesions.

Expression of IL-2R, IL-4R, IL-6R on peripheral blood lymphocytes in systemic lupus erythematosus and correlation with disease activity: a prospective study

AIMS

To study the expression of interleukin-2 receptor (IL-2R), interleukin-4 receptor (IL-4R) and interleukin-6 receptor (IL-6R) on peripheral blood lymphocytes (PBL) in patients with systemic lupus erythematosus (SLE); to correlate the level of expression of these receptors with SLE disease activity.

METHODS

Peripheral blood lymphocytes were studied by a high sensitivity flow cytometry technique using monoclonal antibodies directed against CD25 (IL-2R alpha chain), CD122 (IL-2R beta chain), CD124 (IL-4R), and CD126 (IL-6R). SLE disease activity was scored using the SLE Disease Activity Index, C3 and C4 concentrations, anti-dsDNA level, and absolute lymphocyte count.

RESULTS

Compared with normal controls, PBL from patients with SLE had a higher percentage of CD25+ cells (median 20.8% v 16.5%) and a lower percentage of CD122+ cells (median 13.1% v 22.4%). The difference in CD122+ cells was greater in the CD122weak population than the CD122strong (natural killer cell) population. The percentages of CD124+ and CD126+ PBLs in patients with SLE and controls were similar. On CD25+ cells, the relative antigenic level of the IL-2R alpha chain was significantly higher in patients with SLE (median 2.01 v 1.81). The relative antigenic levels of CD122+, CD124+ and CD126+ cells were similar in patients and controls. Neither the percentages nor the relative antigenic levels of all of these cytokine receptors were correlated with any of the parameters of disease activity.

CONCLUSION

Lymphocyte activation in patients with SLE was evident from the increase in CD25 expression on PBL, with a reciprocal decrease in CD122 expression. As the expression of IL-2R, IL-4R, IL-6R did not correlate with disease activity, it seems that these cytokine/receptor systems do not play a direct role in disease activation in SLE.

Abnormalities of lymphocyte subsets in canine systemic lupus erythematosus

Canine systemic lupus erythematosus (SLE) is a disease clinically very similar to its human counterpart. But so far, no study has reported an accurate evaluation of the lymphocyte subsets in the canine disease. Here, we present a study in which lymphocyte subsets have been evaluated in the peripheral blood of 20 dogs suffering from spontaneous systemic lupus erythematosus (SLE) in active and inactive phases, before and during treatment with prednisone and levamisole. 22 healthy dogs have been used as a control population. We show that canine SLE in active phases is associated with a several lymphopenia (1050 +/- 520 10(6) cells/l versus 2130 +/- 1 020 10(6) cells/l in controls). A striking finding is the imbalance of the CD4 and CD8 subsets (respectively 56.7 +/- 10.7% and 10.9 +/- 3.8% of CD4+ and CD8+ lymphocytes versus 40.5 +/- 11.5% and 18 +/- 4.4% in controls) and a strong activation of T-cells in active phases (64.1 +/- 16.9% of 2B3+ cells versus 46.5 +/- 16.7%). Moreover, we observed a persistence of the T subset imbalance during spontaneous evolution. In contrast, the treatment induced in dogs showing a good response the correction of CD4/CD8 ratio and no clinical manifestations, whereas in low responders no such improvements were observed. Thus, this work suggests that the main immunological imbalance seen in SLE could be associated with defective suppressor cells and provides further evidence of similarity of human and dog SLE.

Restricted junctional diversity of T cell receptor delta gene rearrangements expressed in systemic lupus erythematosus (SLE) patients

SLE is an autoimmune connective tissue disorder affecting multiple organs, in which T cells may play a central role. This study investigated T cell receptor (TCR) gamma/delta repertoire expression in peripheral blood mononuclear cells (PBMC) of SLE patients and healthy individuals using variable (V) gene family-specific polymerase chain reaction (PCR) amplification of TCR cDNA. The expressed V gamma repertoires were diverse in SLE and control PBMC, although V gamma IV gene rearrangements were barely detectable or not expressed in some patients. In contrast, delta chain expression was limited in all SLE patients, with delta transcripts rearranged primarily to the V delta 1 and V delta 2 genes, as opposed to control PBMC, in which all six V delta genes were detected. To assess the clonality of TCR populations, cDNA clones containing rearranged V delta 1, V delta 2 and V gamma 9 transcripts were sequenced from PBMC of both patients and controls. For controls, delta chain junctional region sequences showed extensive molecular heterogeneity, since virtually all 34 V delta 1 and 32 V delta 2 cDNA clones analysed were unique. A few V gamma 9 cDNA clones (3/21) had the same junctional region sequence motif (EVQEL) encoded largely by the V gamma 9 and joining (J) gamma P gene segments. Identical V gamma 9 junctional sequences were found in SLE patients that did not contain the EVQEL motif present in normal peripheral blood gamma/delta lymphocytes. Moreover, the predominant V delta 1-J delta -constant (C) delta and V delta 2-J delta-C delta gene rearrangements expressed in SLE PBMC showed restricted junctional diversity, but the oligoclonal delta transcripts were different in each patient. These findings suggest in vivo oligoclonal expansion of gamma/delta T cells in the periphery of SLE patients in response to a limited number of nominal ligands. Whether gamma/delta T cells contribute to the development of systemic autoimmunity remains to be investigated.

Immunogenetics of chronic liver diseases

The genetic background of autoimmune diseases becomes more and more evident. Immunogenetics comprises the analysis of genes and their products located at the region 6p21 on the short arm of chromosome 6, which is also known as the major histocompatibility complex (MHC). MHC class I and II genes are highly polymorphic. The complement genes C2, C4A, C4B, and BF, which are also polymorphic, became known as MHC class III genes. In autoimmune hepatitis type 1, there is a dual association for white persons with either HLA-A1-B8-DR3 or HLA-DR4. In patients from Japan, autoimmune hepatitis type 1 is predominantly associated with HLA-DR4. This dual association is confirmed at the DNA level. Whereas only limited data are available for autoimmune hepatitis type 2, the association of primary biliary cirrhosis with HLA-DR8 is based on several studies. Primary sclerosing cholangitis is associated with HLA-B8-DR3 and -DR52a. This association was confirmed at the DNA level because of a significant increase of the DRB3*0101 allele. For DRB3*0101-negative individuals, a second association with DRB5*0101 (= DR2) was described. Further analysis of the hypervariable region of the HLA class II molecule indicates that lysine at position 71 is crucial for autoimmune hepatitis type 1 in white persons, whereas position 13 is important for people from Japan. In contrast, leucine at position 35 is important for patients with primary biliary cirrhosis, whereas leucine at position 38 is an important risk factor for primary sclerosing cholangitis. The MHC class III allele C4A-QO is significantly increased in autoimmune hepatitis type 1 and 2 and in primary biliary cirrhosis. Advances in immunogenetics will certainly increase our knowledge of the etiology and pathogenesis of immune-mediated liver diseases, which hopefully will lead to more specific therapeutic interventions.