Distribution of class IIDQ antigens on normal and leukemic lymphoid cells

Constitutive expression of MHC class II genes in melanoma cell lines results from the transcription of class II transactivator abnormally initiated from its B cell-specific promoter

In melanoma cell lines, two different patterns of MHC class II expression have been described, either an IFN gamma-inducible expression of HLA-DR and HLA-DP, with a faint or null expression of HLA-DQ, resembling that described for melanocytes, or a constitutive expression, i.e., IFN-gamma independent, of all three HLA-D isotypes. As this latter phenotype has been associated with a more rapid progression of melanoma tumors, we have analyzed in different melanoma cell lines the molecular mechanisms leading to this abnormal pattern of MHC class II expression. In agreement with the evidence of a coordinate transcription of the HLA-D genes in these cell lines, we have shown the constitutive expression of CIITA (class II transactivator) transcripts, CIITA being known as the master switch of MHC class II expression. Unexpectedly, these transcripts initiate from promoter III of the CIITA gene, a promoter that is mainly used constitutively in B lymphocytes. This expression was further shown to occur through factor(s) acting on the enhancer located upstream of CIITA promoter III, which was previously described in epithelioid cells as an IFN-gamma-response sequence. The hypothesis of a general abnormality of the IFN-gamma transduction pathway was dismissed. Constitutive transcription of CIITA from promoter III having been observed in unrelated melanoma cell lines, we propose the hypothesis that this phenomenon might not be a random event, but could be linked to the neoplasic state of the melanoma cells.

Uncoordinated HLA-D gene expression in a RFXANK-defective patient with MHC class II deficiency

We describe the analysis of a patient, JER, presenting classical immunological features of MHC class II deficiency. Unexpectedly, some HLA transcripts (HLA-DRA, HLA-DQA, and HLA-DMA) were found to be expressed in the JER cell line at nearly wild-type levels, while HLA-DPA and the HLA-D beta-chain transcripts were not detected. Gene reporter experiments confirmed the differential transcriptional activities driven by the HLA-D promoters in the JER cells. A defect in RFXANK was first suggested by genetic complementation analyses, then assessed with the demonstration of a homozygous mutation affecting a splice donor site downstream exon 4 of RFXANK. Because the severe deletion of the resulting protein cannot account for the expression of certain HLA-D genes, minor alternative transcripts of the RFXANK gene were analyzed. We thereby showed the existence of a transcript lacking exon 4, encoding a 28-aa-deleted protein that retains a transcriptional activity. Altogether, we characterize a new type of mutation in the RFXANK gene in a MHC class II-defective patient leading to an uncoordinated expression of the HLA-D genes, and propose that this phenotype is ensured by severely limited amounts of an active, although truncated RFXANK protein.

Ligation of MHC class II molecules differentially upregulates TNF beta gene expression in B cell lines of different MHC class II haplotypes

Although the production of selected cytokines by B cells is important for their regulation, little is known about MHC class II-induced cytokine expression in these cells. We designed the present studies to investigate MHC class II-mediated TNF-beta gene expression in 19 EBV-transformed homozygote B cell lines at similar stage of differentiation but presenting different MHC class II haplotypes. Our results demonstrate that in contrast to PMA, engagement of MHC class II with staphylococcal enterotoxin A (SEA), a natural ligand, or with anti-HLA-DR mAb L243, stimulates TNF-beta gene expression in some but not all B cell lines. The differential stimulation of TNF-beta gene expression via MHC class II was not due to the cells MHC class II expression level, nor to their capacity to bind the ligands as evidenced by SEA binding affinity studies. Together these results demonstrate that ligation of MHC class II molecules can stimulate TNF-beta gene expression in a B cell line-dependent manner. The differential cytokine gene expression might be due to an influence of MHC class II haplotype either by a linkage disequilibrium with TNF-beta gene or by a differential association with effector or cell surface molecules.

Chronic lymphocytic leukaemia: the nature of the leukaemic cell

Far from being the boring, inactive, inert lymphocyte that haematologists of old perceived it to be, the chronic lymphocytic leukaemia (CLL) cell has set us many complex problems. The cell is apparently stuck in G0 in cell cycle, yet expresses many activation markers. The cells apparently manufacture many cytokines and respond in vitro to even more, yet cells entering even G1 are few. The cell surface marker profile is unique. There is apparently no normal equivalent of the CLL cell. In part, this may be because the cell is malignant; malignant cells often express aberrant markers. Consistent chromosomal abnormalities are emerging but we have no idea how these abnormalities translate into molecular mistakes that dictate the peculiar nature of the cell. CLL cells carry a characteristics set of adhesion molecules, but we cannot read their homing and recycling instructions. The outstanding irregularities of the CLL cell are its CD5 positivity and its sparse surface immunoglobulin. This ought to translate as an anergic B1 cell, perhaps programmed for autoimmunity. If the tumour cell were responsible for the patient's production of immunoglobulin or secretion of autoantibodies, then a pattern might have emerged. Alas, these are the product of the normal B cells. How the CLL cell induces these complications is unknown. Thus, despite the information contained in this review, the CLL cell remains a puzzle.

Patterns of intermediate filaments, VLA integrins and HLA antigens in a new human biliary epithelial cell line sensitive to interferon-gamma

BACKGROUND/AIMS

Intra-hepatic bile ducts are the primary site of damage in several immunologically mediated liver diseases. However, immunological processes underlying biliary epithelial cell recognition by T lymphocytes are poorly understood. Therefore, a convenient in vitro model that could mimic these immunologic disorders would be of great interest.

METHODS

A human cell line (HuGB) was established from a metastasis of gallbladder adenocarcinoma in the liver. Intermediate filament expression was analysed by immunostaining, and gamma-glutamyl transpeptidase and albumin secretion were measured. VLA integrin expression pattern, expression of HLA class I and II antigens and ICAM-1 protein were analysed by flow cytometry and their modulation by interferon-gamma was quantitated using a QIFIKIT commercial kit.

RESULTS

Histological analysis showed high similarity between the initial gallbladder adenocarcinoma and the established cell line. Cytokeratins 8 and 19 and vimentin showed strong positive staining in the established cell line. Gamma-glutamyl transpeptidase was secreted by these cells while albumin expression was negative. HuGB cells also expressed VLA-alpha2, VLA-alpha3, VLA-alpha6, VLA-beta1, but not VLA-alpha1, VLA-alpha4 and NCAM, a pattern of adhesion molecule expression compatible with the biliary epithelium. Also, similar to the biliary epithelium found in normal liver, HuGB cells expressed abundant HLA class I but few HLA class II antigens. We found that the expression of HLA antigens and ICAM-1 protein were increased during interferon-gamma treatment of HuGB cell line.

CONCLUSIONS

Both phenotypic and morphological characteristics of HuGB cells suggested their biliary origin. Sensitivity of HuGB cells to interferon-gamma suggests that this new cell line could represent a suitable model to investigate the up-regulation of membrane antigens occurring in immune diseases involving biliary epithelial cells.

Conformation of human leukocyte antigen class II molecules. Evidence for superdimers and empty molecules on human antigen presenting cells

Subpopulations of human leukocyte antigen (HLA) class II molecules were studied in antigen presenting cells. We present evidence for double dimers or "superdimers" of HLA class II molecules that were stable in an SDS solution at room temperature but dissociated when heated to 50 degrees C into 60-kDa alphabeta heterodimers. Development of an immunofluorescence assay allowed us to quantify the expression of HLA antigens as reflected by the number of bound isotype-specific monoclonal antibodies per cell. The total expression of class II (DR, DQ, and DP) augmented 6-fold after a 36-h interferon-gamma (IFNgamma) treatment of freshly isolated monocytes. Next, we used a recombinant and fluorescein-conjugated form of the class II-associated invariant chain as a quantitative probe for empty peptide-binding sites. The fraction of empty class II molecules was 0.73-2.9% in resting monocytes but was reduced to 0. 12-0.5% of the total after IFNgamma treatment. The fraction of empty sites in B lymphocytes was 0.09-0.36%. The mean number of empty sites per cell were: 6.3 x 10(3) (monocytes), 7.2 x 10(3) (IFNgamma-activated monocytes), 5.2 x 10(2) (B lymphocytes), and 3.6 x 10(3) (Raji B cells). A minor population (4.3-7.4% of total cells), which expressed a much higher number of empty sites, was consistently present in all cell types studied.

HLA class-II-mediated homotypic aggregation: involvement of a protein tyrosine kinase and protein kinase C

Homotypic aggregation of B-lymphocytes, B-cell lines and class-II-positive T cells via HLA class II molecules was examined. Signaling via DR antigens induced rapid aggregation in a dose- and time-dependent manner, maximum and stable aggregation was induced within 20 minutes. On the contrary, rapid signaling via DP or DQ required prestimulation with either PMA or anti-sIg. Aggregation was temperature and energy dependent. [Ca2+] and [Mg2+] concentrations and an intact cytoskeleton were required while neither mRNA or protein synthesis were required. Furthermore, FACS analysis revealed that aggregation was not directly correlated with cell surface expression of HLA class II molecules. Our results demonstrate that aggregation was mediated through a protein tyrosine kinase (PTK)-dependent pathway that preceded activation of protein kinase C (PKC) and failure to generate either the PTK signal or the PKC signal prevented aggregation. The contribution of a tyrosine kinase was further demonstrated by the total inhibition of aggregation following treatment with an anti-CD45 mAb.

Class II MHC antigens in normal human skeletal muscle

Class II MHC antigen expression has been investigated in muscle tissue and cultured cells from normal human skeletal muscle by light and electron immunocytochemistry. In muscle tissue, these antigens were detected in satellite cells, interstitial cells, and blood vessels. In cultures, muscle cells were stained with a pan-reactive anti-HLA class II antibody and with isotypes specific for DP, DQ, and DR. The staining was present on mononucleated cells and persisted on myotubes; it was stronger for DR and DQ isotypes than for DP. At the subcellular level, staining was located not only at the cell surface, but also next to the endoplasmic reticulum and in the cytosol. Thus, myosatellite cells and aneurally cultured cells from human normal skeletal muscle express class II MHC antigens. Moreover, the myotube staining and the presence of gold particles inside the cells suggested synthesis of these antigens after myoblast fusion.

T cell response to myelin basic protein epitopes in multiple sclerosis patients and healthy subjects

T cell lines and clones specific for human myelin basic protein (BP) were selected from three multiple sclerosis (MS) patients and two healthy subjects and tested for their proliferative responses to a battery of synthetic peptides, 9 to 21 amino acid residues long. The combined amino acid sequence of the peptides spanned the complete sequence of the human BP. The results suggest the development of T cells sensitized to at least four independent regions of the human BP, indicating some diversity of the human T cell repertoire to BP. However, an immunodominant T cell epitope was located in the C-terminal region, defined by residues 149-162. This epitope was recognized by T cells from three subjects out of five (one MS patient and both healthy controls) in the context of different DR specificities. Another epitope (located in the 57-75 region) which triggered one MS patient's T cell response was also recognized by a mycobacteria-specific T cell clone cross-reacting with BP.

HLA class-II antigen-mediated induction of a proliferative response to anti-IgM in human B lymphocytes

Signal transduction via HLA class-II antigens has been studied using human resting B lymphocytes and monoclonal anti-HLA class-II antibodies. An increased intracellular calcium flux, phosphatidylinositol biphosphate hydrolysis and activation of protein kinase C have all been observed following signal transduction via HLA-class-II molecules. The interaction of HLA-class-II-mediated signalling with sIg-mediated signalling has been studied using a non-mitogenic anti-sIg. This combination provides a model for T-cell-dependent antigenic stimulation. The results demonstrate that stimulation via HLA class-II antigens permits a proliferative response to an otherwise non-mitogenic anti-sIg and that this effect is not restricted to one HLA class-II isotype. These data suggest that HLA-class-II-mediated signalling is important in responses to T-cell-dependent antigens.

Normal B cell compartment in chronic lymphatic leukemia

In contrast to normal B lymphocytes, CLL cells express CD5 antigen believed to be a T cell marker. We have assessed normal and malignant B cell compartments in CLL patients with the aid of two-colour immunofluorescence techniques (CD5-TRITC, DR-FITC). No clear correlation was found between progression of disease and parameters studied. However, there was a tendency for a diminution of normal B cells in advanced stages of disease.

Expression of MHC class I and class II antigens in colonic carcinomas

Malignant and non-malignant ('normal') colonic tissues from patients with colonic carcinoma were examined for the expression of MHC class I and class II antigens by immunoenzymatic staining using monoclonal antibodies. The amount of class I antigen as detected by 2 monoclonal antibodies, FMC 16 or W6/32 was clearly diminished in 11 of 14 tumours when compared to the amount present on 'normal' colonic tissue from the same individual. The loss of class I antigen did not correlate with tumour stage or differentiation. The reactivities of FMC 16 and W6/32 with these tissues were not identical, which indicates that the 2 monoclonal antibodies may recognize different epitopes on the HLA class I molecule. Class II antigens were absent from 'normal' colonic epithelium but were present on 20 of 28 tumours, with DR being detected more often than DP, and DQ found only on 4 of 28 tumours. When present, staining for class II antigens was heterogeneous within the tumour, in that all tumour cells did not stain equally. DR and DP antigens were found more often on moderately or poorly differentiated adenocarcinomas and on stage B, C and D tumours in that order of frequency. Thus tumours with a better prognosis were less likely to express DR and DP. The expression of DQ was unrelated to staging or differentiation.

Congenital self-healing histiocytosis (Hashimoto-Pritzker). An ultrastructural and immunohistochemical study

Congenital self-healing histiocytosis (CSHH) is a rare primary histiocytic skin disorder. Only a few cases have been studied by ultrastructure and immunohistochemistry. Here we report a new case that was investigated using an electron microscope and a panel of monoclonal (MCA) and polyclonal (PCA) antibodies. CSHH cells were found to bear the immunohistochemical phenotype of normal epidermal Langerhans cells (LC) and histiocytosis X (HX) cells (CD1a/c+, CD1b-, CD4+/-, human leukocyte antigen [HLA]-DR/DQ+, S-100+). However, an electron microscope showed a paucity of Birbeck granule (BG)-containing cells. This contrasted with their immunophenotype. This finding, along with other ultrastructural characteristics of CSHH cells, suggests that histologic differences exist between CSHH and HX. However, because no absolute histologic criterion is known that allows unequivocally the differential diagnosis between the two diseases, this distinction currently has to rely on clinical criteria, mainly the regressive course observed within a few months in CSHH. The precise nosologic position of CSHH among other histiocytic syndromes remains unsettled.

Differential expression of HLA-DR, HLA-DP, HLA-DQ and associated invariant chain (Ii) in normal colorectal mucosa, adenoma and carcinoma

The expression of MHC class II antigens (HLA-DR, HLA-DP and HLA-DQ) and the associated invariant chain (Ii) was studied in epithelial cells of normal colorectal mucosae, colorectal adenomas and carcinomas, using a sensitive immunoperoxidase technique with monoclonal antibodies on frozen sections. In contrast to class II antigens, Ii was detected in some normal mucosae distant from the tumour. In residual non-neoplastic mucosa adjacent to carcinomas, Ii and class II antigens were induced in the order Ii greater than or equal to HLA-DR greater than or equal to HLA-DP greater than or equal to HLA-DQ, the reactions being most pronounced in cases with inflammatory alteration of the crypts. In 22/37 adenomas and 77/123 carcinomas, Ii expression clearly exceeded class II antigen expression. Class II antigens were found in 20/37 adenomas and 62/123 carcinomas, mostly in a non-coordinate manner, following the above order. A detailed analysis of the expression patterns in normal and neoplastic colon epithelial cells revealed a closer association of HLA-DP with HLA-DQ than of HLA-DR with HLA-DP, or HLA-DQ.

B-cell lymphomas of high-grade malignancy frequently lack HLA-DR, -DP and -DQ antigens and associated invariant chain

The expression of HLA-DR, HLA-DP and HLA-DQ antigens was studied in an unselected series of 66 B-cell lymphomas by means of immunohistology using monoclonal antibodies against non-polymorphic determinants in a sensitive immunoperoxidase technique. In addition, the expression of the MHC class-II antigen-associated invariant chain (li) was examined. The tumors were classified according to the Kiel classification, 30 being of high-grade and 36 being of low-grade malignancy. Only 6 lymphomas of high-grade and 16 lymphomas of low-grade malignancy showed coordinate strong expression of all HLA class-II antigens and invariant chain as observed in the normal peripheral B cell. Six further tumors of high-grade and 8 tumors of low-grade malignancy contained tumor-cell subsets with reduced expression of one or several of the antigens. Eighteen lymphomas of high-grade and 12 lymphomas of low-grade malignancy contained varying tumor-cell subsets that were negative for HLA-DR, -DP, -DQ and li in a selective or combined manner. Three highly malignant tumors were devoid of all class-II antigens and li; 2 highly malignant tumors expressed invariant chain only. The presence of high-grade malignancy was significantly correlated with the occurrence of tumor cells lacking HLA-DR (p = 0.004), HLA-DP (p = 0.013), HLA-DQ (p = 0.007) or li (p = 0.024).

Improvement of decreased interleukin 2 (IL-2) responsiveness and IL-2 production in autologous mixed-lymphocyte reaction of cord blood lymphocytes by interferon-gamma and IL-2 and the role of HLA-DQ antigen

Cord blood T cells did not produce interleukin 2 (IL-2) nor acquire responsiveness to it in autologous mixed-lymphocyte reaction (AMLR) as they do when activated by phytohemagglutinin (PHA). The ability of the cells to respond to IL-2 was restored either by the addition of recombinant IL-2 to the AMLR culture or by the preculture of non-T stimulator cells with recombinant interferon-gamma (IFN-gamma). IL-2 production was also induced when the T cells were added with recombinant IL-2 at the initiation of the AMLR culture, preceded by the treatment of non-T cells with recombinant IFN-gamma. IL-2-producing cells of cord blood induced in the above-mentioned condition were defined to be OKT4+ T cells, because the deletion of OKT4+ T cells from T-cell population abrogated the reaction, while that of OKT8+ T cells did not. Acquisition of IL-2 responsiveness and IL-2 production of T cells seemed to be mediated by HLA-DR and HLA-DQ molecules of non-T cells because these reactions were blocked by the treatment of non-T cells either with monoclonal anti-HLA-DR or with anti-HLA-DQ antibody. The HLA-DR and HLA-DQ densities of cord blood non-T cells were low as compared with those of adult, but the expression of HLA-DQ was remarkably improved by IFN-gamma treatment. In regard to IL-2, both IFN-gamma and IL-2 were needed to enable the lymphocytes to produce. This may suggest that some functional maturation by IL-2 of responder T cells is further required. These combined data suggested that cord blood non-T cells are defective as a stimulator in AMLR and this could be corrected by enhancing the expression of HLA-DQ antigen.

Changes in cell surface antigen expression on human articular chondrocytes induced by gamma-interferon. Induction of Ia antigens

Ia antigens (class II HLA molecules) have been detected on cells eluted from affected human cartilage in certain disease states, but not on normal cartilage cells. Because the presence of Ia antigens on chondrocytes may play an important role in rheumatic diseases, we investigated the induction of these molecules by gamma-interferon (gamma-IFN), a potent Ia-inducing lymphokine. Human articular chondrocytes were incubated with recombinant gamma-IFN, and the expression of Ia antigens was studied by cell sorter analysis, using a panel of reagents that detect monomorphic and polymorphic specificities of the DR and DQ Ia antigen families. While the induction of DR antigens, including polymorphic DR specificities, was readily obtained with gamma-IFN (50-95% positive cells), DQ antigens were negative or were displayed only on a lower percentage of chondrocytes (5-60%). In addition, incubation with gamma-IFN led to an increased expression of HLA class I antigens. The expression of various other surface markers either remained unchanged (as in 4F2 and BA-2) or showed tendencies toward decreased percentages (as in 83c2) or increased percentages (as in M phi R-17). No apparent change in cell morphology or growth pattern was observed.

Characterization of a monoclonal antibody recognizing a monomorphic determinant of the alpha chain of class II DQ antigens

We have characterized a monoclonal antibody (L2) specific for a determinant of Human DQ class II antigens. After immunoprecipitation and immunofluorescence analysis performed on a panel of DR homozygous cell lines and HLA deleted mutants, it behaves like a monomorphic anti-DQ reagent and does not react with the products of the various DR alleles. On immunoblotting, it reacts with an epitope of the DQ alpha chain.

Heterogeneity of responsiveness of chronic lymphocytic leukemic B cells to B cell growth factor or interleukin 2

We compared the proliferative responses of purified human leukemic B cells from 12 cases of chronic lymphocytic leukemia to highly purified B cell growth factor (BCGF) and recombinant interleukin 2 (rIL 2) spontaneously, and in a coactivation assay using anti-mu monoclonal antibodies. Heterogeneity of response to one or the other lymphokine was observed from case to case. Spontaneous responses were observed to BCGF in one case, to rIL 2 in 3 cases and to both lymphokines in one other case. Costimulation with anti-mu monoclonal antibody induced a proliferative response to BCGF in 3 additional cases and to rIL 2 in 4 cases. Interestingly, cells from BCGF-responsive cases also proliferated in response to rIL 2. The leukemic B cells from 4 chronic lymphocytic leukemia patients were unresponsive. Cells from 5 cases expressed IL 2 receptors, although rIL 2 induced a direct proliferative response in only 3 of these cases. Expression of the B cell activation antigen B5 was associated to BCGF responsiveness.