Expression of MHC class II antigens in human B-cell leukaemia and non-Hodgkin's lymphoma

The small molecule antibody mimic SH7139 targets a family of HLA-DRs expressed by B-cell lymphomas and other solid cancers

Selective high-affinity ligands (SHALs) belong to a novel class of small-molecule cancer therapeutics that function as targeted prodrugs. SH7139, the most advanced of the SHAL drugs designed to bind to a unique β-subunit structural epitope located on HLA-DR10, has exhibited exceptional preclinical efficacy and safety profiles. A comparison of SH7139 and SH7129, a biotin derivative of the drug developed for use as a diagnostic, showed the incorporation of a biotin tag did not alter the SHALs ability to target or kill HLA-DR10 expressing Raji cells. The use of SH7129 in an immuno-histochemical type assay to stain peripheral blood mononuclear cells (PBMCs) obtained from individuals expressing specific HLA-DRB1 alleles has also revealed that in addition to HLA-DR10, seven other more commonly expressed HLA-DRs are targeted by the drug. Computational dockings of the SHAL's recognition ligands to a number of HLA-DR structures explain, in part, why the targeting domains of SH7129 and SH7139 bind to some HLA-DRs but not others. The results also substantiate the selectivity of SH7129 and suggest it may prove useful as a companion diagnostic for pre-screening biopsy samples to identify those patients whose tumours should respond to SH7139 therapy.

T cell exhaustion characterized by compromised MHC class I and II restricted cytotoxic activity associates with acute B lymphoblastic leukemia relapse after allogeneic hematopoietic stem cell transplantation

Acute B lymphoblastic leukemia (B-ALL) relapse contributes predominantly to the mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the mechanism of B-ALL relapse after allo-HSCT remains unknown. The eradication of leukemia after allo-HSCT largely relies on graft-versus-leukemia (GVL) effects mediated by donor T cells. T cell exhaustion, characterized by the increased expression of inhibitory receptors and impaired function, may suppress GVL effects. In this study, we evaluated whether T cell exhaustion was involved in B-ALL relapse after allo-HSCT. The results showed that CD4⁺ and CD8⁺ T cells exhibited increased coexpression of PD-1 and Tim-3, and compromised proliferative capacity, cytokine production and cytotoxic potentials in relapsed patients. Additionally, T cells at the tumor site were more easily exhausted than T cells in the peripheral blood. Moreover, the reversal of T cell exhaustion might correlate with effective anti-leukemic responses after reinduction. These results suggested that T cell exhaustion was associated with B-ALL relapse after allo-HSCT as well as its treatment outcome.

Human leukocyte antigens and genetic susceptibility to lymphoma

Familial aggregation, coupled with ethnic variation in incidence, suggests that inherited susceptibility plays a role in the development of lymphoma, and the search for genetic risk factors has highlighted the contribution of the human leukocyte antigen (HLA) complex. In a landmark study published almost 50 years ago, Hodgkin lymphoma (HL) was the first disease to be associated with HLA variation. It is now clear that Epstein-Barr virus (EBV)-positive and -negative HL are strongly associated with specific HLA polymorphisms but these differ by EBV status of the tumours. HLA class I alleles are consistently associated with EBV-positive HL while a polymorphism in HLA class II is the strongest predictor of risk of EBV-negative HL. Recent investigations, particularly genome-wide association studies (GWAS), have also revealed associations between HLA and common types of non-Hodgkin lymphoma (NHL). Follicular lymphoma is strongly associated with two distinct haplotypes in HLA class II whereas diffuse large B-cell lymphoma is most strongly associated with HLA-B*08. Although chronic lymphocytic leukaemia is associated with variation in HLA class II, the strongest signals in GWAS are from non-HLA polymorphisms, suggesting that inherited susceptibility is explained by co-inheritance of multiple low risk variants. Associations between B-cell derived lymphoma and HLA variation suggest that antigen presentation, or lack of, plays an important role in disease pathogenesis but the precise mechanisms have yet to be elucidated.

Impaired T-Cell Function in B-Cell Lymphoma: A Direct Consequence of Events at the Immunological Synapse?

Tumors can escape immune destruction through the development of antigen loss variants and loss of antigen processing/presentation pathways, thereby rendering them invisible to T cells. Alternatively, mechanisms of peripheral T-cell tolerance that would normally be important for protection from the development of autoimmunity may also be co-opted to (i) generate an immuno-inhibitory tumor environment, (ii) promote development of regulatory cell populations, or (iii) cell-intrinsically inactivate tumor-specific T cells. Emerging evidence suggests that T-cell function is impaired in hematological malignancies, which may manifest from cognate interactions between T cells and the tumor. The immunological synapse forms the cognate T-cell and antigen-presenting cell interaction and is the site where key signalling events, including those delivered by co-inhibitory receptors, that determine the fate of T cells occur. Here, we review evidence that events at the immune synapse between T cells and malignant B cells and alterations in immune synapse function may contribute to loss of T-cell function in B-cell malignancies.

Nonproteolytic roles of 19S ATPases in transcription of CIITApIV genes

Accumulating evidence shows the 26S proteasome is involved in the regulation of gene expression. We and others have demonstrated that proteasome components bind to sites of gene transcription, regulate covalent modifications to histones, and are involved in the assembly of activator complexes in mammalian cells. The mechanisms by which the proteasome influences transcription remain unclear, although prior observations suggest both proteolytic and non-proteolytic activities. Here, we define novel, non-proteolytic, roles for each of the three 19S heterodimers, represented by the 19S ATPases Sug1, S7, and S6a, in mammalian gene expression using the inflammatory gene CIITApIV. These 19S ATPases are recruited to induced CIITApIV promoters and also associate with CIITA coding regions. Additionally, these ATPases interact with elongation factor PTEFb complex members CDK9 and Hexim-1 and with Ser5 phosphorylated RNA Pol II. Both the generation of transcripts from CIITApIV and efficient recruitment of RNA Pol II to CIITApIV are negatively impacted by siRNA mediated knockdown of these 19S ATPases. Together, these results define novel roles for 19S ATPases in mammalian gene expression and indicate roles for these ATPases in promoting transcription processes.

NKT cell adjuvant-based tumor vaccine for treatment of myc oncogene-driven mouse B-cell lymphoma

Immunomodulators are effective in controlling hematologic malignancy by initiating or reactivating host antitumor immunity to otherwise poorly immunogenic and immune suppressive cancers. We aimed to boost antitumor immunity in B-cell lymphoma by developing a tumor cell vaccine incorporating α-galactosylceramide (α-GalCer) that targets the immune adjuvant properties of NKT cells. In the Eμ-myc transgenic mouse model, single therapeutic vaccination of irradiated, α-GalCer-loaded autologous tumor cells was sufficient to significantly inhibit growth of established tumors and prolong survival. Vaccine-induced antilymphoma immunity required NKT cells, NK cells, and CD8 T cells, and early IL-12-dependent production of IFN-γ. CD4 T cells, gamma/delta T cells, and IL-18 were not critical. Vaccine treatment induced a large systemic spike of IFN-γ and transient peripheral expansion of both NKT cells and NK cells, the major sources of IFN-γ. Furthermore, this vaccine approach was assessed in several other hematopoietic tumor models and was also therapeutically effective against AML-ETO9a acute myeloid leukemia. Replacing α-GalCer with β-mannosylceramide resulted in prolonged protection against Eμ-myc lymphoma. Overall, our results demonstrate a potent immune adjuvant effect of NKT cell ligands in therapeutic anticancer vaccination against oncogene-driven lymphomas, and this work supports clinical investigation of NKT cell-based immunotherapy in patients with hematologic malignancies.

Partial plasma cell differentiation as a mechanism of lost major histocompatibility complex class II expression in diffuse large B-cell lymphoma

Loss of major histocompatibility complex class II (MHC II) expression is associated with poor patient outcome in diffuse large B-cell lymphoma (DLBCL). As MHC II molecules are lost with plasmacytic differentiation in normal cells, we asked whether MHC II loss in DLBCL is associated with an altered differentiation state. We used gene expression profiling, quantum dots, and immunohistochemistry to study the relationship between MHC II and plasma cell markers in DLBCL and plasmablastic lymphoma (PBL). Results demonstrate that MHC II(-) DLBCL immunophenotypically overlap with PBL and demonstrate an inverse correlation between MHC II and plasma cell markers MUM1, PRDM1/Blimp1, and XBP1s. In addition, MHC II expression is significantly higher in germinal center-DLBCL than activated B cell-DLBCL. A minor subset of cases with an unusual pattern of mislocalized punctate MHC II staining and intermediate levels of mRNA is also described. Finally, we show that PBL is negative for MHC II. The results imply a spectrum of MHC II expression that is more frequently diminished in tumors derived from B cells at the later stages of differentiation (with complete loss in PBL). Our observations provide a possible unifying concept that may contribute to the poor outcome reported in all MHC II(-) B-cell tumors.

The insulator factor CTCF controls MHC class II gene expression and is required for the formation of long-distance chromatin interactions

Knockdown of the insulator factor CCCTC binding factor (CTCF), which binds XL9, an intergenic element located between HLA-DRB1 and HLA-DQA1, was found to diminish expression of these genes. The mechanism involved interactions between CTCF and class II transactivator (CIITA), the master regulator of major histocompatibility complex class II (MHC-II) gene expression, and the formation of long-distance chromatin loops between XL9 and the proximal promoter regions of these MHC-II genes. The interactions were inducible and dependent on the activity of CIITA, regulatory factor X, and CTCF. RNA fluorescence in situ hybridizations show that both genes can be expressed simultaneously from the same chromosome. Collectively, the results suggest a model whereby both HLA-DRB1 and HLA-DQA1 loci can interact simultaneously with XL9, and describe a new regulatory mechanism for these MHC-II genes involving the alteration of the general chromatin conformation of the region and their regulation by CTCF.

Fully human antibody exhibits pan-human leukocyte antigen-DR recognition and high in vitro/vivo efficacy against human leukocyte antigen-DR-positive lymphomas

HD8, a fully human monoclonal antibody specific for human leukocyte antigen-DR (HLA-DR), was generated by using the transchromosome mouse that bears the human immunoglobulin genes. HD8 could bind to all 13 tested HLA-DR-positive cell lines and 35 B-cells from healthy donors. Epitope mapping revealed that while the antibody recognizes the most polymorphic region of the HLA-DRB chain, its critical epitope residues are conserved in the major alleles. Indeed, HD8 could recognize 99.2% of HLA-DRB alleles. Since its essential epitope residues are also largely conserved in HLA-DP and HLA-DQ, HD8 could recognize 100% and 66% of the HLA-DP and HLA-DQ alleles tested, respectively. HD8 exerted strong antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro, and significantly extended the life span of immunocompromised mice inoculated with non-Hodgkin lymphoma cell lines. The HD8 antibody may be highly useful in HLA-DR-targeted immunotherapy as it is likely to evoke similarly strong responses in individuals carrying different HLA-DR alleles.

Antitumour activity mediated by CD4+ cytotoxic T lymphocytes against MHC class II-negative mouse hepatocellular carcinoma induced by dendritic cell vaccine and interleukin-12

When BALA/c mice with BNL hepatocellular carcinoma (HCC) were treated with dendritic cells fused with BNL cells (DC/BNL) and recombinant murine interleukin (IL)-12, tumour development was significantly suppressed, whereas treatment with either DC/BNL or IL-12 alone did not show a tumour-suppressive effect. Antitumour activity induced by DC/BNL + IL-12 was abrogated by depletion of CD4+ T cells, but not by depletion of CD8+ T cells or natural killer cells. Splenic CD4+ T cells and CD8+ T cells from DC/BNL-treated mice showed cytotoxic activity against BNL cells after 3 days of incubation with DC/BNL, although BNL cells do not express major histocompatibility complex (MHC) class II molecules even after treatment with interferon (INF)-gamma. Furthermore, CD4+ T cells killed syngeneic-irrelevant CT26 cells and even allogeneic Hepa1-6 cells. This cytotoxicity was blocked by concanamycin A, but not by an anti-Fas ligand (FasL) monoclonal antibody, indicating that cytotoxic activity was mediated by perforin. Immunofluorescence microscopy demonstrated that abundant CD4+ T cells and MHC class II-positive macrophages, but not CD8(+) T cells, had infiltrated tumour tissue in mice treated with DC/BNL + IL-12. Flow cytometric analysis of tumour-infiltrating cells in mice treated with DC/BNL + IL-12 showed increases in CD4+ T cells and MHC class II+ CD11b+ cells but not in CD8+ T cells or MHC class I+ CD11b+ cells. Our results suggest that, in BNL-bearing mice treated with DC/BNL + IL-12, tumour macrophages activated by INF-gamma produced by IL-12-stimulated T cells might present BNL tumour antigens and activate DC/BNL-primed CD4+ cytotoxic T lymphocytes (CTLs) in a MHC class II-dependent manner, leading to perforin-mediated bystander killing of neighbouring MHC class II-negative tumour cells.

Chaperoning antigen presentation by MHC class II molecules and their role in oncogenesis

Tumor vaccine development aimed at stimulating the cellular immune response focuses mainly on MHC class I molecules. This is not surprising since most tumors do not express MHC class II or CD1 molecules. Nevertheless, the most successful targets for cancer immunotherapy, leukemia and melanoma, often do express MHC class II molecules, which leaves no obvious reason to ignore MHC class II molecules as a mediator in anticancer immune therapy. We review the current state of knowledge on the process of MHC class II-restricted antigen presentation and subsequently discuss the consequences of MHC class II expression on tumor surveillance and the induction of an efficient MHC class II mediated antitumor response in vivo and after vaccination.

High numbers of tumour-infiltrating activated cytotoxic T lymphocytes, and frequent loss of HLA class I and II expression, are features of aggressive B cell lymphomas of the brain and testis

Loss of both HLA class I and class II expression in B cell lymphomas is a mechanism of escape from a cytotoxic T lymphocyte (CTL) immune response and will therefore give a strong selective survival advantage in tumours expressing strong immunogenic antigens. We investigated loss of HLA expression using specific antibodies on tissue sections from 254 B cell lymphomas originating from nodal and different extranodal sites in relation to numbers of tumour-infiltrating T cells. Complete loss of HLA class I and II was observed in a minority of the nodal, stomach, and skin lymphomas but in the majority of the lymphomas originating from the testis and the CNS. Interestingly, relatively high percentages of activated CTLs were detected in both primary testicular and CNS lymphomas compared to lymphomas at other sites, with highest percentages in the testis (p < 0.0001). We conclude that loss of both HLA class I and II expression occurs very frequently in lymphomas originating from the testis and the CNS as compared to nodal and some other extranodal sites. The presence of high percentages of activated CTLs in the testicular and CNS lymphomas suggests that loss of HLA expression provides a strong growth advantage for lymphoma cells in these immune-privileged sites.

Microarray analysis of B-cell lymphoma cell lines with the t(14;18)

The t(14;18) is the most common genetic alteration in follicular lymphoma, and is detectable in a subset of diffuse large B-cell lymphomas (DLBCL), resulting in over-expression of the anti-apoptotic protein BCL-2. Although the t(14;18)-induced over-expression of BCL-2 is an important step in lymphomagenesis, this aberration alone is not sufficient to produce malignant lymphoma. Further analysis of these tumors is needed to identify additional genes that might be involved in the genesis of follicular lymphoma and progression to DLBCL. To address this issue, we analyzed the gene expression profiles of four t(14;18)-positive cell lines and two t(11;14)-positive mantle-cell lymphoma cell lines using cDNA microarrays containing 4364 genes, and compared them to the genetic profile of phenotypically purified B-cells obtained from hyperplastic tonsils. A total of 137 genes were differentially expressed by approximately twofold or more in the t(14;18) cell lines relative to tonsillar B-cells. 68 genes were up-regulated, 69 genes were down-regulated, and approximately 20% of the differentially regulated genes had no known function. The up-regulated genes included a number of genes involved in the promotion of cellular proliferation and survival, as well as cell metabolism. Down-regulated genes included mediators of cell adhesion and negative regulators of cell activation and growth. Hierarchical clustering analysis separated the t(14;18) and mantle-cell lines into distinct groups based on their gene expression profiles. We confirmed the differential expression of approximately 80% of selected up- and down-regulated genes identified by microarray analysis by quantitative real-time fluorescence reverse transcriptase polymerase chain reaction (RT-PCR) analysis and/or immunoblotting. This study demonstrates the utility of cDNA microarray analysis for the assessment of global transcriptional changes that characterize t(14;18)-positive cell lines, and also for the identification of novel genes that could potentially contribute to the genesis and progression of non-Hodgkin's lymphomas with this translocation.

Extensive genetic alterations of the HLA region, including homozygous deletions of HLA class II genes in B-cell lymphomas arising in immune-privileged sites

In B-cell lymphomas, loss of human leukocyte antigen (HLA) class I and II molecules might contribute to immune escape from CD8+ and CD4+ cytotoxic T cells, especially because B cells can present their own idiotype. Loss of HLA expression and the possible underlying genomic alterations were studied in 28 testicular, 11 central nervous system, and 21 nodal diffuse large B-cell lymphomas (DLCLs), the first two sites are considered as immune-privileged sites. The analysis included immunohistochemistry, loss of heterozygosity analysis, and fluorescent in situ hybridization (FISH) on interphase cells and isolated DNA fibers. Total loss of HLA-A expression was found in 60% of the extranodal cases and in 10% of the nodal cases (P < .01), whereas loss of HLA-DR expression was found in 56% and 5%, respectively (P < .01). This was accompanied by extensive loss of heterozygosity within the HLA region in the extranodal DLCLs. In 3 cases, retention of heterozygosity for D6S1666 in the class II region suggested a homozygous deletion. This finding was confirmed by interphase FISH that showed homozygous deletions in the class II genes in 11 of the 18 extranodal lymphomas but in none of the 7 nodal DLCLs (P < .001). Mapping by fiber FISH showed variable deletions that always included HLA-DQ and HLA-DR genes. Hemizygous deletions and mitotic recombinations often involving all HLA genes were found in 13 of 18 extranodal and 2 of 7 nodal lymphomas. In conclusion, a structural loss of HLA class I and II expression might help the B-cell lymphoma cells to escape from immune attack.

Extensive genetic alterations of the HLA region, including homozygous deletions of HLA class II genes in B-cell lymphomas arising in immune-privileged sites

In B-cell lymphomas, loss of human leukocyte antigen (HLA) class I and II molecules might contribute to immune escape from CD8+ and CD4+ cytotoxic T cells, especially because B cells can present their own idiotype. Loss of HLA expression and the possible underlying genomic alterations were studied in 28 testicular, 11 central nervous system, and 21 nodal diffuse large B-cell lymphomas (DLCLs), the first two sites are considered as immune-privileged sites. The analysis included immunohistochemistry, loss of heterozygosity analysis, and fluorescent in situ hybridization (FISH) on interphase cells and isolated DNA fibers. Total loss of HLA-A expression was found in 60% of the extranodal cases and in 10% of the nodal cases (P &lt; .01), whereas loss of HLA-DR expression was found in 56% and 5%, respectively (P &lt; .01). This was accompanied by extensive loss of heterozygosity within the HLA region in the extranodal DLCLs. In 3 cases, retention of heterozygosity for D6S1666 in the class II region suggested a homozygous deletion. This finding was confirmed by interphase FISH that showed homozygous deletions in the class II genes in 11 of the 18 extranodal lymphomas but in none of the 7 nodal DLCLs (P &lt; .001). Mapping by fiber FISH showed variable deletions that always included HLA-DQ and HLA-DR genes. Hemizygous deletions and mitotic recombinations often involving all HLA genes were found in 13 of 18 extranodal and 2 of 7 nodal lymphomas. In conclusion, a structural loss of HLA class I and II expression might help the B-cell lymphoma cells to escape from immune attack.

Primary mediastinal large cell lymphoma

PURPOSE

Primary mediastinal large cell lymphoma PMLCL is a recently described entity which has provoked considerable interest lately. The unique immunophenotype of the malignant cell, as well as conflicting reports regarding its response to therapy, prompted us to review the current literature focusing on the pathological and clinical aspects of this disease.

DESIGN

We reviewed the current literature that contained details on the clinical presentation, pathological profile and clinical outcome.

RESULTS

Most reports agree that PMLCL typically affects a young female population and presents with symptoms related to compression of mediastinal structures. Pathologically, the malignant cells may arise from a distinctive thymic medullary B cell subpopulation which is characterized by the following phenotype: CD19+, CD21-, CD20+, CD22+. Alterations of c-myc and lack of expression of HLA class 1 antigens on the tumour cell surface have been described. Response to treatment and clinical outcome have varied from one series to another and is possibly explained by the small number of patients in most series and by the heterogeneity of therapy. In general, the outcome does not appear to be worse than that of other large cell lymphomas although, given the young age of these patients, it might be expected to be more favourable.

CONCLUSIONS

Primary mediastinal large cell lymphoma is a distinct clinico-pathological entity characterized by: (1) a predominance of young adults; (2) female predominance (female/male ratio of 2:1) in contrast to the other large cell lymphomas; (3) CD19+/CD21- immunophenotype; (4) absence of HLA-class 1 antigen expression; (5) possible involvement of c-myc; (6) frequent dissemination at relapse to unusual anatomic sites in a pattern reminiscent of Burkitt's lymphoma. The role of radiotherapy and the optimal treatment for this disorder are issues that remain unresolved.

Major histocompatibility complex class I and class II antigen expression in diffuse large cell and large cell immunoblastic lymphomas. Absence of a correlation between antigen expression and clinical outcome

The major histocompatibility complex (MHC) class I (HLA-A, B, C) and class II (HLA-DR) antigens are involved in cell-to-cell recognition and in regulating the immune response. Others have shown previously that MHC class I and class II antigens may be absent in a subset of malignant lymphomas, prompting the hypothesis that the absence of MHC antigen expression may be one of the mechanisms involved in the growth and dissemination of malignant lymphomas (by allowing a neoplasm to escape immune surveillance). To address this hypothesis, we analyzed MHC class I and class II (HLA-DR) antigen expression by diffuse large cell and large cell immunoblastic lymphomas in 88 and 117 patients, respectively, using frozen sections and the monoclonal antibodies W6/32 (HLA-A, B, C), anti-beta 2-microglobulin, and L203 (HLA-DR). Although there were no statistically significant clinical differences by MHC class II antigen expression, a small group of patients with MHC class I antigen-negative lymphomas were significantly younger (P = 0.03), less often had small neoplasms (P = 0.03), and were treated with doxorubicin-based chemotherapy more frequently (P = 0.04) than those with antigen-positive lymphomas. However, neither MHC class I nor class II antigen expression by the lymphomas consistently correlated with patient survival or freedom from relapse. This lack of correlation was true for all patients assessed, as well as for the subsets of patients with B-cell lymphomas, T-cell neoplasms, or those treated with doxorubicin-based chemotherapy. In accordance with previously published studies, stage, presence of B symptoms, and treatment with doxorubicin-based chemotherapy were of prognostic importance in univariate or multivariate analyses for survival or freedom from relapse. The findings may be considered evidence against the hypothesis that the absence of MHC class I or II antigen expression by malignant lymphomas plays a role in their tumorigenicity. However, we cannot completely exclude the possibility that the therapies used for this group of patients may have obscured any effect that MHC antigen expression exerts on prognosis.

Intravesical Evans strain BCG therapy: quantitative immunohistochemical analysis of the immune response within the bladder wall

Previous studies have demonstrated that is is the local immune response which is of importance for the anti-tumour activity of BCG therapy. We have investigated this by quantitative immunohistochemical analysis of serial bladder mucosal biopsies taken before, during and after an eight week course of intravesical Evans strain BCG therapy and three monthly thereafter in 16 patients (15 extensive CIS and one extensive G2pTa papillary tumour). This particular group of patients had a 67% complete response rate at six months post-treatment. The main findings on immunohistochemical analysis were the universal induction of MHC Class II antigens by urothelial cells which was statistically significant up to 6 months after completion of therapy, coupled with a T cell dominated cystitis. Increases in CD3+ T cell infiltration of the lamina propria and that of the CD4+ "Helper" subset which predominated were significant up to 3 months post-therapy and these cells showed evidence of increased immunological activation as shown by increased interleukin-2 receptor and MHC Class II antigen expression. There were also significant increases in CD68+ macrophage and the incidence of CD22+ B cell aggregates but CD57+ NK cells were sparse both before and after therapy. The degree of mononuclear cell infiltration for all markers examined (except CD57) was significantly greater in those biopsies in which the urothelial cells expressed MHC Class II antigens than in those that did not. Also the degree of T cell infiltration (CD3, CD4 and CD8) was significantly greater in the eight patients deemed to have had a complete response compared to those seven with a partial response or treatment failure. These results are discussed in terms of possible mechanisms of action for BCG therapy and in particular the role of enhanced antigen presentation by tumour cells.

Expression of MHC class II antigens (HLA-DR, -DP, and -DQ) on human gastric epithelium

Class II antigen expression on gastric epithelium was investigated using an immunoperoxidase method in relation to the degree of inflammatory cell infiltration in the lamina propria. Sixty-six biopsy specimens from 43 patients with chronic gastritis were examined. The frequency of HLA-DR expression in specimens with cell infiltration was 94%, while that in specimens without cell infiltration was 24%. There was significant difference in the frequency of HLA-DR expression between the two groups (P less than 0.01). HLA-DR was most intensely expressed in the glandular neck portion. The frequency and extent of class II antigen expression on gastric epithelium with cell infiltration were in the following order: DR greater than DP greater than DQ. The extent of DR and DP, but not DQ expression generally paralleled the degree of cell infiltration. Intestinal metaplasia was found in 13 specimens. In the area of intestinal metaplasia, epithelial class II staining was absent except for one specimen. These results suggest that the respective genes of three class II antigens are regulated by different mechanisms and that an immunological mechanism plays a role in the pathogenesis of gastritis.

HLA-DR expression in B-cell non-Hodgkin's malignant lymphomas: a multiparameter flow cytometry study

Ten cases of reactive follicular hyperplasia and 31 cases of B-cell non-Hodgkin's malignant lymphoma were studied using multiparameter flow cytometry. A bimodal distribution for HLA-DR expression, but not for surface immunoglobulin or B cell-specific antigens CD19 and CD20, was observed commonly in mixed cell type and infrequently in non-mixed cell type B-cell malignant lymphomas. On the basis of HLA-DR distribution alone, 31 cases of B-cell malignant lymphomas of low, intermediate, and high grades could be separated into mixed and non-mixed cell types, with only two misclassifications (P = 0.0001). Exceptionally, one case of malignant lymphoma, follicular and diffuse, mixed-cell type had a unimodal HLA-DR distribution, and one case of malignant lymphoma, diffuse, large noncleaved cell type had a bimodal HLA-DR distribution. In all cases of malignant lymphoma, follicular, mixed-cell type studied, low HLA-DR was correlated with small cells, and high HLA-DR was correlated with large cells. In contrast, HLA-DR expression and cell size were not as directly correlated in cases of malignant lymphoma, diffuse, mixed-cell type. These observations suggest that most, but not all, cases of B-cell malignant lymphomas of the mixed cell type can be separated from other B-cell lymphomas on the basis of HLA-DR distribution.

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.

Recurrent mutation of immunoglobulin and c-myc genes and differential expression of cell surface antigens occur in variant cell lines derived from a Burkitt lymphoma

The phenotypic and molecular genetic characteristics of 4 variant sublines of the Burkitt lymphoma cell line Namalwa have been examined. The sublines are DNA-fingerprint-identical and derived from a monoclonal tumour, as shown by a rearrangement of the T-cell-receptor beta-chain gene common to the 4 sublines. There is non-co-ordinate expression of MHC class-I MHC class-II, surface immunoglobulin and a number of antigens recognized by CD MAbs on the different sublines. These different phenotypes of the cells are reminiscent of B cells arrested in varying states of cellular maturity. On Southern blots there are different patterns of restriction fragments hybridizing with Ig heavy- and light-chain gene probes among the sublines, indicating that multiple rearrangements or mutations of Ig genes have occurred in the cells. Different patterns of hybridizing fragments among the sublines were also found by using c-myc probes, implying the existence of different mutations of the c-myc locus. The c-myc mutation found in one of the sublines mapped to the 5' flanking sequence and in another 3' to the c-myc locus. Using the J17BS8 probe, which detects a restriction fragment length polymorphism in the 3' flanking region of the c-myc gene, a 4-fold variation in the gene copy number among the subline was found and one of the sublines was shown to be hemizygous for c-myc. Examination of DNA from early cultures of Namalwa cells showed that the alternations in Ig and c-myc structure had occurred on prolonged culture of the cells.

The identification of antigens in antibody/antigen complexes using high performance liquid chromatography

A method for the identification of antigens in a complex mixture of proteins is described. It exploits the effect which addition of a monoclonal antibody and resultant formation of antibody/antigen complexes has on the apparent retention time of the antigen on a size exclusion column. An antigen in the mixture can be identified as that component whose retention time is decreased by addition of its antibody. The principle of the method is demonstrated using an HPLC size exclusion column (DuPont GF450) and three MoAbs, PD7/26, DA6 147 and W6/32 which are directed against three antigens of the lymphocyte surface, the leucocyte-common antigen, class II MHC and class I MHC respectively.

Immunopathology of the placenta in pemphigoid gestationis and linear IgA disease

We have investigated the immunopathology of the placenta in bullous diseases by studying the deposition of immune complexes and expression of MHC class II subregion products by immunohistological methods. Placentae from seven patients with pemphigoid gestationis (PG) and two patients with linear IgA disease were studied. In PG immune complexes containing IgGI and C3 were identified in six cases. In linear IgA disease IgAI containing immune complexes were found in both cases. Placentae from patients with PG showed aberrant expression of MHC Class II products. This was not seen in the placentae from patients with linear IgA disease. In PG there was incoordinate expression of the subregion products, DP and DR being more extensively and consistently expressed than DQ. These results and previous immunogenetic studies suggest that PG may be unique among organ specific autoimmune disease, the autoantibodies forming during an allogenic response rather than target cells behaving as antigen presenting cells.

HLA class II sublocus expression in benign and malignant breast epithelium

Using immunohistochemistry and a panel of five monoclonal antibodies, the epithelial expression of HLA class II sublocus products by benign and malignant breast has been studied. The magnitude of the stromal mononuclear inflammatory cell infiltrate was assessed. There was expression of HLA class II by 75 per cent of epithelial cells in the benign tissues, with little variation in intensity and between antibodies. There was coordinate expression of DR and DQW1. Epithelial expression by carcinomas was more complex and variable. Most (61 per cent) carcinomas exhibited variable loss of epithelial expression of class II products, as detected by three antibodies recognizing epitopes on DP, DQ, and DR together. Thirteen (28 per cent) carcinomas were completely negative or had very occasional positive cells. The extent of this loss was unrelated to the magnitude of the inflammatory infiltrate and axillary lymph node status. No well-differentiated carcinomas exhibited complete loss. Furthermore, non-coordinate expression of DR and DQW1 was present in 8 out of 40 carcinomas, with the proportion of DQW1 positive epithelium always being less than that of DR. Carcinomas exhibiting non-coordinate expression were never well differentiated; there was no relationship with the extent of the inflammatory infiltrate. This is the first study to detail HLA class II expression in breast, and our results suggest that alterations in expression of these products may modify or reflect tumour behaviour.

HLA class II antigen expression and the autoimmune thyroid response in patients with benign and malignant thyroid tumors

To further understand the relationship between the immune system and the neoplastic human thyroid cell we investigated the degree of intrathyroidal lymphocytic infiltration and thyroid HLA class II expression in 17 patients with thyroid tumors. In another 60 thyroid tumor patients the association of thyroidal lymphocytic infiltration with thyroid autoantibody production was analyzed. In total 117 thyroid tissues were examined including tissue obtained at autopsy (n = 28), fetal thyroid tissue (n = 4), thyroid samples obtained from areas distant from benign follicular adenomas (n = 5), and 80 abnormal thyroids including patients with benign (n = 53) or malignant (n = 24) thyroid tumors and Hashimoto's thyroiditis (n = 3). Normal adult and fetal thyroid tissue had no significant lymphocytic infiltration and no detectable HLA-DR, -DP, or -DQ antigens on their thyroid follicular epithelial cells. The degree of lymphocytic infiltration in the nonneoplastic thyroid tissue of thyroid glands with benign and malignant thyroid tumors varied considerably and correlated with the presence and titer of serum thyroid autoantibodies measured by sensitive ELISA techniques. However, all but one of the benign follicular adenomas had thyroid cells negative for HLA class II determinants despite the presence of infiltrating lymphocytes, while 7 of 10 thyroid carcinomas expressed class II antigen (principally HLA-DR) even when only minor degrees of lymphocytic infiltration were present. These data indicate a correlation between lymphocytic infiltrates and serum thyroid autoantibody titers but the relationship with HLA class II expression is more complex. Since we have previously shown that HLA class II antigen expression can be induced by local interferon-gamma secretion, presumably from activated T cells, we conclude that estimates of simple thyroid lymphocytic infiltration and serum autoantibody secretion do not correlate with the degree of intrathyroidal T-cell activation. Furthermore, our observation of increased expression of HLA class II antigens in thyroid cancer suggests considerable cellular heterogeneity in susceptibility to HLA class II antigen induction in human thyroid disease.

Regulation of malignant B-cell proliferation by direct binding of anti-HLA class-II antibodies

A panel of five monoclonal antibodies (Mab) and a polyclonal antiserum directed against HLA class II were studied for their effect on growth of mature neoplastic B cells of prolymphocytic origin (B-PLL cells). The polyclonal antiserum and three out of five monoclonal antibodies were able to synergize with phorbol myristate acetate (PMA) to induce proliferation of B-PLL cells of one patient. Cross-blocking experiments showed that the proliferation-inducing Mab recognized closely related epitopes on HLA class-II molecules. The other two monoclonal antibodies recognized different epitopes on HLA class-II molecules and had no effect on proliferation of B-PLL cells. Proliferation induced by the combination of PMA and anti-HLA class-II Mab was inhibited by anti-CD18 (LFA-1) antibodies and was extremely dependent on cell density. This study indicates that certain HLA class II determinants on neoplastic B cells can transduce growth-promoting signals.

Major histocompatibility complex (MHC) class II antigen (HLA-DR, DQ, and DP) expression in human fetal endocrine organs and gut

Monoclonal antibodies were used to analyse adrenal, pancreas, thyroid, and gut samples from human fetuses (14-19 weeks estimated gestational age; EGA) for the presence of class II major histocompatibility complex (MHC) antigens (HLA-DR, DQ, DP) by immunohistochemistry. In the adrenal definitive and fetal cortex, HLA-DR+, DP-, DQ- cells were clearly demonstrated. These DR+ cells were identified, phentotypically, as predominantly tissue macrophages and a small population of CD45R+, IgM+ lymphoid cells. Within the pancreas, numerous cells throughout the tissue were strongly DR+ but DQ-; DP+ cells were not observed until 17 weeks EGA. Using a double-labelling procedure, minor proportions of these DR+ cells were identified as macrophages or as (CD19+) B cells, while endocrine and endothelial cells were negative. Throughout the thyroid, small numbers of DR+ macrophages and small lymphoid cells were detected, although the thyroid epithelial cells were DR-, DP-, and DQ-. Large numbers of DR+, DP+, DQ- cells were observed in the stomach wall and mucosa. In the intestine, DR+, DP+, DQ+ cells positive for all MHC class II loci products were abundant throughout the lamina propria and lymphoid aggregates. The class II antigens appeared in the proportion DR greater than DP greater than DQ and expression was most prevalent in the mid-gut region. A small proportion of epithelial cells of the villi along the gut were weakly DR+ but DQ-, DP-. These results show that DR+ cells in fetal endocrine tissue are mainly 'passenger leucocytes' and that, in contrast to recent reports concerning normal adult tissue, the adrenal and pancreatic endothelial cells are DR-.

Activation and differentiation antigen expression in B-cell non-Hodgkin's lymphoma

In an attempt to establish whether extended immuno-phenotyping allows more accurate definition of subgroups of B-cell non-Hodgkin's lymphoma (NHL) we have stained a series of 145 cases with a large panel of monoclonal antibodies that recognize B-cell differentiation and activation antigens. No antigen was expressed by all cases. The B-cell histogenesis in many cases could be confirmed only by using a panel of immunoglobulin and pan B-cell markers. There was marked phenotypic heterogeneity within and between major groups of B-cell NHL as delineated by the Kiel classification although the differentiation antigens CD5 (lymphocytic and centrocytic NHL) and OKT10 (plasma cell tumours) were more often expressed by certain morphological groups. The activation antigens 4F2 and transferrin receptor were expressed more strongly and more often by high grade NHL but other activation antigens (CD23 and CD25) were not more frequently associated with these tumours. Extended phenotyping may be of value in improving the understanding of biological abnormalities and processes involved in B-cell NHL, but we conclude that a limited panel of markers (CD3, CD5, CD22, CD45, IgM, kappa, and lambda) should be sufficient for routine diagnosis and classification of most cases.

Differential expression of MHC class II antigens in chronic B-cell disorders

Cells from the peripheral blood of 22 patients with chronic B-cell disorders were examined for the expression of surface MHC class II antigens. We made use of well-characterized monoclonal antibodies (McAbs) specific for HLA-DP, -DQ and -DR molecules (B7/21, Tü22, RFDR1 and RFDR2) and of another McAb, RFD1, associated with the class II system. By using indirect immunofluorescence and flow cytometry we found both non-coordination and heterogeneity in expression of MHC class II antigens but generally with a hierarchy of positivity: DR greater than DQ greater than DP. This suggests a sequence of gradual acquisition of HLA-D antigens and indicates distinct differences in maturation arrest of the individual cases. However, after treatment with phorbol ester TPA and calcium ionophore A23187, all cases expressed the previously absent molecules indicating that the structural genes for these products remained intact. TPA and A23187 increased both the number of positive cells in most cases and the fluorescence staining intensities of all class II markers including RFD1. Thus, leukaemic cells may express different combinations of class II antigens reflecting: (i) a predetermined order of gradual acquisition of class II molecules; (ii) differences in the stages of maturation arrest; and (iii) in the cases of disordered expression a desynchronized regulation of these markers.

B prolymphocytic leukemia cell lines: phenotype and response to B cell differentiation factor

Three recently-derived cell lines of prolymphocytic leukemia origin were studied. The phenotype of the cells, analysed in terms of expression of immunoglobulin and other B cell maturation markers, indicates that the cells are mature B lymphocytes close to the plasma cell stage of differentiation. All three cell lines secrete IgM, and two of the three lines respond to B cell differentiation factor with an increased secretion of IgM.

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).

Epstein-Barr virus-transformed human precursor B cell lines: altered growth phenotype of lines with germ-line or rearranged but nonexpressed heavy chain genes

A series of lymphoblastoid cell lines (LCLs) have been established by in vitro infection of fetal bone marrow and fetal liver cells with Epstein-Barr virus (EBV). While most lines showed the usual mature B cell phenotype, a small proportion were cytoplasmic and surface immunoglobulin (Ig) heavy and light chain negative. Analysis of gene rearrangements indicated that the Ig- lines were either germ-line or nonproductively rearranged when probed for JH and were in germ-line configuration for C chi; no mu or chi mRNA could be detected in such cells. Precursor B cell lines were indistinguishable from their normal Ig+ counterparts in their expression of a wide variety of cell surface markers including "activation" antigens usually associated with the lymphoblastoid state; even the single LCL showing germ-line heavy and light chain genes expressed B lineage-specific cell surface antigens. However, the Ig- lines were distinct from their Ig+ counterparts in three important respects: (a) they grew much more slowly and achieved lower saturation densities, (b) they showed unusually high proportions (8-16%) of cells in EBV-productive cycle, and (c) they contained unusually high proportions (up to 40%) of cells expressing free joining (J) chain. These results suggest that precursor B cells differ in their response to the growth-transforming effects of EBV such that the virus-cell interaction in precursor B cell lines is inherently less stable than in conventional LCL. In particular there may be a greater movement of cells out of cycle and along the B cell maturation pathway. It is possible that such movement leads in individual cells either to virus replication or to a "sterile" plasmacytoid differentiation with J chain expression in the absence of Ig synthesis.

Variant sublines of the human B-lymphoma cells Namalwa are at different stages of differentiation

Variant sublines of the Burkitt's lymphoma cell line Namalwa, previously shown to differ in MHC class II antigen and immunoglobulin expression, have been tested with monoclonal antibodies defining B-cell specific clusters of differentiation (CD). The Namalwa sublines express antigens recognized by the CD antibodies in patterns that indicate that the cells are arrested at different stages of differentiation.

Anti-HLA-class II monoclonal antibodies inhibit polyclonal B cell differentiation in vitro at the accessory cell level

We produced and characterized a panel of anti-HLA class II monoclonal antibodies (mAb) to study the inhibition of T cell-dependent B cell differentiation. The newly produced mAb belonged to different isotypes and subclasses, and recognized at least two different nonpolymorphic HLA class II determinants. We found that anti-HLA class II mAb inhibited the pokeweed mitogen (PWM)- and interleukin 2-driven T cell-dependent IgM synthesis, but did not affect the phorbol myristate acetate-, phytohemagglutinin-, anti-T3- or PWM-induced T cell proliferation. Moreover, when the mAb were tested in a monocyte-independent B cell differentiation assay in which T cells are activated by insoluble anti-T3 mAb in the absence of accessory cells, no effect was seen on IgM synthesis. These data indicate that inhibition of T cell-dependent B cell differentiation by anti-HLA class II mAb is caused by interference with an accessory cell function essential for B cell differentiation.

Major histocompatibility complex class II antigen expression in B and T cell non-Hodgkin's lymphoma

An immunohistochemical study of 46 B and T cell non-Hodgkin's lymphomas, using monoclonal antibodies to the products of the major histocompatibility complex (MHC) class II antigen subregions, DP, DQ, and DR, showed that most B and T cell lymphomas express these antigens. Both coordinate and non-coordinate expression of MHC class II antigens was observed, but this did not correlate with immunological phenotype, morphological grade, or proliferation index as determined by flow cytometry.

Keratinocyte expression of MHC class II antigens in allergic sensitization and challenge reactions and in irritant contact dermatitis

Keratinocytes expressed major histocompatibility complex class II antigens during the development of irritant contact dermatitis, and during the induction of contact hypersensitivity, as well as in established allergic contact dermatitis. A battery of anti-class II monoclonal antibodies, some of which are specific for class II subregion products (DP, DQ, DR), was used in an immunohistochemical study of the sequential changes in the allergic challenge reactions to dinitrochlorobenzene (DNCB) and nickel, the irritant response to anthralin, and the induction of sensitization to DNCB. The induction of keratinocyte class II expression paralleled the influx of Leu-3a+ T cells into the skin and had occurred by 24 or 48 h in each type of reaction. Differential expression of class II subregion products on keratinocytes was noted: DR was the most frequently expressed molecule, followed by DP and DQ, although in the irritant response, DP expression was not observed. The importance of these observations can be decided only by functional studies.

MHC class II antigen and immunoglobulin expression in spontaneous phenotypic variants of the Burkitt's lymphoma cell line Namalwa

Phenotypic variant sublines of the Burkitt's lymphoma cell line Namalwa were examined with cDNA probes for the different MHC class II beta chain genes and with monoclonal antibodies specific for the corresponding cell surface antigens (DP, DQ and DR antigens). Expression of MHC class II antigens in the Namalwa sublines (known as CSN/70, IPN/45, PNT and KN2) was compared with that of the B-lymphoblastoid cell line DEW1, which is identical to Namalwa in DR allotype (DR 2,4). There were markedly different levels of expression of MHC class II antigens among the cell lines: in DEW1 and the Namalwa KN2 subline DP, DQ and DR antigens were expressed on almost all the cells. On the PNT and IPN/45 sublines, DR antigens were expressed on all the cells, and DP and DQ antigens were expressed at detectable levels on only a proportion of cells. On CSN/70, there was weak expression of DR antigens on a minority of cells and no detectable expression of DP and DQ antigens. When examined with MHC class II-specific cDNAs, restriction fragment patterns of DNA were identical for all the cell lines, suggesting that they had structurally identical MHC class II genes. In the Namalwa cell lines the synthesis of Ig and the expression of MHC class II antigens were coordinately regulated.

The primary mediastinal clear cell lymphoma of B-cell type has variable defects in MHC antigen expression

Eight cases of the recently reported 'primary mediastinal clear cell lymphoma of B-cell type' (Möller et al., 1986) were examined immunohistologically for the expression of cytoplasmic and/or surface antigens of MHC class I and II with mAbs directed against framework determinants of HLA-A,B,C (W6/32; B9.12.1), HLA-DP,DR,DQ (2.06), -DQ (Leu 10; Tü22), -DR (Tü34) gene products, and with mAbs specific for beta 2-microglobulin (BBM-1) and the HLA-D associated invariant chain (Vic-Y1). Besides the reported Ig-deficiency, the neoplastic B-cells of 7/8 tumours have variable defects in MHC antigen expression. Three lack both class I and class II antigens, one tumour lacks class I antigens but expresses HLA-DQ and -DR on the majority of neoplastic cells, three others contain varying proportions of MHC-antigen deficient tumour cells. The expression of Ii is closely correlated with HLA-D(R) expression and its antigenic sites are strictly located in the cytoplasm. Against the background of current knowledge, the variable and occasionally severe defects in MHC antigen expression within the herein presented series of B-cell lymphomas suggest that this unusual feature might be another characteristic of a novel lymphoma type.

Expression of HLA-D sub-region products on human colorectal carcinoma

The major histocompatibility complex (MHC) status of normal, inflamed, pre-malignant and malignant epithelia of the human gastrointestinal tract was investigated by immunocytochemical methods using monoclonal antibodies (MAbs) directed against heavy (alpha)- and light (beta 2m)-chain Class-I molecules and sub-locus products (DP, DQ, DR) of the HLA-D region. Class-I expression on epithelial cells appeared to vary little with pathological status except in the case of 4/32 (13%) colorectal carcinomas in which the antigens were undetectable or scanty. The pattern of Class-II expression was more complex. The antigens were readily detectable on normal stomach epithelium, in villous adenomas and in inflammatory bowel mucosa. In each of these situations DR was the predominant specificity, followed by DP and DQ. Expression on normal colonic epithelium was usually negative but, in the vicinity of a neoplasm or an area of marked leukocyte infiltration, Class-II molecules (DR greater than DP much greater than DQ) were detectable. A similar pattern of non-coordinate expression was found on 23/32 (72%) colorectal carcinomas, but on the remaining 28% no Class-II products were detectable, under conditions wherein stromal leukocytes were strongly stained. The data suggest that in a significant proportion (nearly 30%) of primary colorectal carcinomas, the capacity for Class-II induction, a constitutive or acquired feature of normal colorectal epithelium, is either diminished or lost. Also, tumor Class-II status is not correlated to Dukes' stage or differentiation.