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

Expression of the Classical and Nonclassical HLA Molecules in Breast Cancer

Considering that downregulation of HLA expression could represent a potential mechanism for breast carcinogenesis and metastasis, the aim of the present study was to use immunohistochemical methods to analyze the expression of HLA-Ia, HLA-DR, HLA-DQ, HLA-E, and HLA-G in invasive ductal carcinoma (IDC) of the breast and to relate this HLA profile to anatomopathological parameters. Fifty-two IDC from breast biopsies were stratified according to histological differentiation (well, moderately, and poorly differentiated) and to the presence of metastases in axillary lymph nodes. The expression of HLA molecules was assessed by immunohistochemistry, using a computer-assisted system. Overall, 31 (59.6%) out of the 52 IDC breast biopsies exhibited high expression of HLA-G, but only 14 (26.9%) showed high expression of HLA-E. A large number (41, 78.8%) of the biopsies showed low expression of HLA-Ia, while 45 (86.5%) showed high expression of HLA-DQ and 36 (69.2%) underexpressed HLA-DR. Moreover, 24 (41.2%) of 52 biopsies had both low HLA-Ia expression and high HLA-G expression, while 11 (21.2%) had low HLA-Ia expression and high HLA-E expression. These results suggest that, by different mechanisms, the downregulation of HLA-Ia, HLA-E, and HLA-DR and the upregulation of HLA-G and HLA-DQ are associated with immune response evasion and breast cancer aggressiveness.

Metronomic administration of the drug GMX1777, a cellular NAD synthesis inhibitor, results in neuroblastoma regression and vessel maturation without inducing drug resistance

High-risk neuroblastoma is a rapidly growing tumor with a survival rate below 50%. A new treatment strategy is to administer chemotherapeutic drugs metronomically, i.e., at lower doses and frequent intervals. The aim of the study was to investigate the effects of GMX1777, a chemotherapeutic drug affecting cellular energy metabolism, in a mouse model for high-risk neuroblastoma. Female SCID mice were injected s.c. with MYCN-amplified human neuroblastoma cells and randomized to either treatment with GMX1777 or vehicle. In some animals, treatment was discontinued allowing tumor relapse. Treatment response was evaluated using the pediatric preclinical testing program (PPTP). Immunohistochemistry and qRT-PCR was performed on tumor cryosections to investigate the microscopic and molecular changes in tumors in response to GMX1777. Despite an increase in vessel density, tumor regression and a high group response score according to PPTP criteria was induced by GMX1777 without inducing drug resistance. Treatment resulted in inhibition of tumor cell proliferation, vessel maturation, reduced hypoxia, increased infiltration of MHC class II negative macrophages and expansion of the nonvascular stromal compartment. Decreased stromal VEGF-A and PDGF-B mRNA in response to treatment together with the structural data suggest a "deactivation" or "silencing" of the tumor stroma as a paracrine entity. In conclusion, GMX1777 was highly efficient against high-risk neuroblastoma xenografts through modulation of both the tumor cell and stromal compartment.

Regulation of major histocompatibility complex class II gene expression, genetic variation and disease

Major histocompatibility complex (MHC) class II molecules are central to adaptive immune responses and maintenance of self-tolerance. Since the early 1970s, the MHC class II region at chromosome 6p21 has been shown to be associated with a remarkable number of autoimmune, inflammatory and infectious diseases. Given that a full explanation for most MHC class II disease associations has not been reached through analysis of structural variation alone, in this review we examine the role of genetic variation in modulating gene expression. We describe the intricate architecture of the MHC class II regulatory system, indicating how its unique characteristics may relate to observed associations with disease. There is evidence that haplotype-specific variation involving proximal promoter sequences can alter the level of gene expression, potentially modifying the emergence and expression of key phenotypic traits. Although much emphasis has been placed on cis-regulatory elements, we also examine the role of more distant enhancer elements together with the evidence of dynamic inter- and intra-chromosomal interactions and epigenetic processes. The role of genetic variation in such mechanisms may hold profound implications for susceptibility to common disease.

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.

Two-phase appearance of oral epithelial dysplasia resulting from focal proliferation of parabasal cells and apoptosis of prickle cells

BACKGROUND

One of the histologic characteristics of epithelial dysplasias of the oral mucosa is droplet-shaped rete processes resulting from a solid proliferation of basaloid cells. These basaloid cells are suddenly changed into an overlay of parakeratotic cells. However, it is unknown how this characteristic two-phase appearance is generated.

METHODS

Formalin-fixed paraffin sections of the oral mucosal specimens with normal, hyperplastic, dysplastic epithelia and squamous cell carcinomas were examined for apoptosis by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) method and for lymphoid cells by immunohistochemistry.

RESULTS

Apoptotic cells were only located in the keratinized layer of normal/hyperplastic epithelia. However, in epithelial dysplasias, apoptotic cells were scattered in the middle or even in the lower parts of the epithelial layer with frequent vacuolation changes of epithelial cells. Within the epithelial layer of dysplasias, there were increased number of lymphocytes, which were immunopositive for CD45RO, CD8, and CD57- and CD68-immunopositive (+), S-100 protein-positive and major histocompatibility complex (MHC) class II-positive monocytic lineages. They increased in number with the severity of dysplastic degrees, and they were often located in the vicinity of apoptotic epithelial cells, but decreased in carcinomas in situ and invasive carcinomas, which contained fewer numbers of apoptotic figures.

CONCLUSION

The findings indicate that intraepithelial infiltrations of both cytotoxic T cells and natural killer cells are closely related to the apoptotic phenomena of prickle cells, which may result in the characteristic 'two-phase appearance' of epithelial dysplasia.

Human cytomegalovirus disrupts constitutive MHC class II expression

CD8(+) and CD4(+) T lymphocytes are important in controlling human CMV (HCMV) infection, but the virus has evolved protean mechanisms to inhibit MHC-based Ag presentation and escape T lymphocyte immunosurveillance. Herein, the interaction of HCMV with the MHC class II Ag presentation pathway was investigated in cells stably transfected with class II transactivator. Flow cytometry experiments demonstrate that HCMV infection decreases cell-surface MHC class II expression. HCMV down-regulates MHC class II surface expression without a significant effect on class II RNA or steady-state protein levels. SDS-stability and confocal microscopy experiments demonstrate normal levels of steady-state peptide-loaded class II molecules in infected cells and that class II molecules reach late endosomal and HLA-DM positive peptide-loading compartments. However, MHC class II positive vesicles are retained in an abnormal perinuclear distribution. Finally, experiments with a mutant HCMV strain demonstrate that this novel mechanism of decreased MHC class II expression is not mediated by one of the known HCMV immunomodulatory genes. These defects in MHC class II expression combined with previously identified CMV strategies for decreasing MHC class I expression enables infected cells to evade T lymphocyte immunosurveillance.

Glomeruloid microvascular proliferation follows adenoviral vascular permeability factor/vascular endothelial growth factor-164 gene delivery

Glomeruloid bodies are a defining histological feature of glioblastoma multiforme and some other tumors and vascular malformations. Little is known about their pathogenesis. We injected a nonreplicating adenoviral vector engineered to express vascular permeability factor/vascular endothelial growth factor-164 (VPF/VEGF(164)) into the ears of athymic mice. This vector infected local cells that strongly expressed VPF/VEGF(164) mRNA for 10 to 14 days, after which expression gradually declined. Locally expressed VPF/VEGF(164) induced an early increase in microvascular permeability, leading within 24 hours to edema and deposition of extravascular fibrin; in addition, many pre-existing microvessels enlarged to form thin-walled, pericyte-poor, "mother" vessels. Glomeruloid body precursors were first detected at 3 days as focal accumulations of rapidly proliferating cells in the endothelial lining of mother vessels, immediately adjacent to cells expressing VPF/VEGF(164). Initially, glomeruloid bodies were comprised of endothelial cells but subsequently pericytes and macrophages also participated. As they enlarged by endothelial cell and pericyte proliferation, glomeruloid bodies severely compromised mother vessel lumens and blood flow. Subsequently, as VPF/VEGF(164) expression declined, glomeruloid bodies devolved throughout a period of weeks by apoptosis and reorganization into normal-appearing microvessels. These results provide the first animal model for inducing glomeruloid bodies and indicate that VPF/VEGF(164) is sufficient for their induction and necessary for their maintenance.

The human hair follicle immune system: cellular composition and immune privilege

The immunology of the hair follicle, its relationship with the 'skin immune system' and its role in hair diseases remain biologically intriguing and clinically important. In this study, we analysed the immunoreactivity patterns of 15 immunodermatological markers to determine the cellular composition and immune privilege of the human hair follicle immune system in anagen VI (growth phase). The most prominent cells located in or around the hair follicle were Langerhans cells, CD4+ or CD8+ T cells, macrophages and mast cells, whereas B cells, natural killer cells and gammadelta T cells were found very rarely. Langerhans cells (CD1a+, major histocompatibility complex, MHC class II+), and T cells (CD4+ or CD8+) were predominantly distributed in the distal hair follicle epithelium, whereas macrophages (CD68+, MHC class II+) and mast cells (Giemsa+) were located in the perifollicular connective tissue sheath. Transmission electron microscopy confirmed low numbers of immune cells in the proximal hair follicle epithelium, and very few macrophages and Langerhans cells were seen in the dermal papilla. Melanophages were observed in the connective tissue sheath and dermal papilla. MHC class I (HLA-A, -B, -C) and beta2-microglobulin immunoreactivity was found on most skin cells, but was substantially reduced on isthmus keratinocytes and virtually absent in the proximal hair follicle epithelium. Apart from the absence of Fas ligand immunoreactivity, the sharply reduced numbers of T cells and Langerhans cells, and the virtual absence of MHC class I expression all suggest that the anagen proximal hair follicle constitutes an area of immune privilege within the hair follicle immune system, whose collapse may be crucial for the pathogenesis of alopecia areata.

Why do B cell lymphoma fail to elicit clinically sufficient T cell immune responses?

There is no doubt that human B cell lymphoma does not elicit a clinically sufficient T cell mediated immune response that results in tumor rejection. However, the mechanisms leading to this lack of T cell recognition and effector function are still not fully understood. Many potential mechanisms such as "ignorance" including "antigen silencing", "tolerance" including "infectious tolerance" and "anergy" or "immunosuppression" have been identified in different model systems and all these could, in part, account for the lack of immune recognition in B cell lymphoma. Malignant B cells are poor antigen presenting cells and T cells in close proximity to the malignant cells are hyporesponsive with detects in T cell receptor signaling and cytotoxic effector function. This review will discuss recent in vitro findings in context of in vivo data in murine model systems relevant to B cell lymphoma. Understanding these complex defects of anti-lymphoma immune responses should allow us to redefine our immunotherapeutic strategies to overcome these detects and induce clinically sufficient T cell mediated immune responses.

An immunohistochemical study of HLA-DR and alpha 1-antichymotrypsin-positive cells in the pulp of human non-carious and carious teeth

The condition of the pulp tissue was classified into seven groups according to the progression of carious lesions from stages S0 (non-carious teeth) to S6 (exposed pulp). There was a small number of anti-HLA-DR antibody-positive cells in the pulp of the early carious teeth, and a markedly increased number at S5 and S6. The recruitment of a large number of anti-HLA-DR cells concomitant with a marked increase of other kinds of immunocompetent cells in the pulp of late-stage caries might indicate the occurrence of antigen presentation followed by both cell-mediated and humoral immune reactions. The number of anti-alpha 1-antichymotrypsin (ACT) antibody-positive macrophages showed a proportional increase with the development of caries, and these cells may be involved in protecting against the tissue damage caused by proteases released from inflammatory cells, as well as having a defensive role by phagocytosis of toxic micro-organisms and damaged tissue residues. Thus anti-HLA-DR and anti-ACT antibody-positive cells might participate in both an efficient immune system and a tissue-protective mechanism in the human dental pulp.

HLA antigen expression in enteropathy associated T cell lymphoma

AIMS

To investigate the occurrence of abnormal patterns of HLA-ABC and HLA-DR expression in enteropathy associated T cell lymphoma and to relate such abnormalities to the Epstein Barr virus (EBV) status of the tumours.

METHODS

Eleven enteropathy associated T cell lymphomas were immunostained with HC10 (HLA-ABC heavy chain) and TAL 1B5 (HLA-DR alpha chain) monoclonal antibodies and polyclonal anti-beta 2 microglobulin (beta 2m, the HLA-ABC light chain) antibodies. In situ hybridisation for EBV using EBER probes was performed on all cases.

RESULTS

Tumour cells of two of 11 patients were EBER positive. One of these showed partial, and the other, complete loss of beta 2m. HLA-DR expression was undetectable in both patients. Of the remaining nine EBER negative tumours, two were HLA-ABC heavy chain negative or showed only occasional positive cells and five of nine showed partial or complete loss of the HLA-ABC light chain, beta 2m. Seven of the nine cases were either negative for HLA-DR or showed weak expression in a proportion of tumour cells.

CONCLUSIONS

These data show that low or absent HLA-ABC and HLA-DR antigen expression occurs commonly in enteropathy associated T cell lymphoma. These abnormal patterns of HLA expression may be associated with escape from immune attack which, in a minority of patients, could be directed against EBV antigens.

Modulation of HLA-DR and CD1a expression on human cornea with low-dose UVB irradiation

PURPOSE

To evaluate the effects of low-dose UVB irradiation of HLA and CD1a expression and the toxic effects of UVB on human corneas.

METHODS

24 pairs of human corneas from 24 donors were studied. One cornea from each pair was randomly irradiated with UVB (100 mJ/cm2) after enucleation. All corneas were then organ-cultured for 2, 7, 14 or 21 days. Endothelium was studied after enucleation and organ culture. Following preservation, corneas were evaluated by means of light microscopy, morphometry and TEM. HLA and CD1a staining was performed using an immuno-alkaline-phosphatase technique.

RESULTS

Endothelial cell loss during organ culture averaged 9.1% in the UVB group and 9.2% in the control group (NS). The number of rosette and reformation figures (p = 0.004) and the coefficient of variation (p = 0.014) were higher in the control group. Epithelial sloughing was more accentuated in the UVB group. We observed the same moderate ultrastructural injuries in both groups. In the epithelium, the average number of HLA-DR+ cells per field was 0.12 in the UVB group and 0.42 in the control group (p = 0.035). In the stroma, these figures were respectively 1.04 and 1.34 (p = 0.026). In the epithelium, the average number of CD1a + cells was respectively 0. 025 and 0.078 (p = 0.019). In the preservation mediums, the average percentage of CD1a + cells was 0.07% in the UVB group and 0.27% in the control group (p = 0.014).

CONCLUSIONS

Low-dose UVB (100 mJ/cm2) decreases HLA-DR and CD1a expression of organ-cultured human corneas and induces moderate corneal injuries. Low-dose UVB might be useful for preventing allograft rejection.

Phenotype and function of peripheral and prostatic lymphocytes in patients with benign prostatic hyperplasia

In a previous report, we demonstrated intense lymphocytic infiltration of all benign prostatic hypertrophy (BPH) tissues analyzed in conjunction with HLA-DR expression on normally MHC-class-II-negative prostate epithelial cells. The composition of these infiltrates (70 to 80% CD3+ T-cells, but no granulocytes) resembles the situation seen in immune responses against altered self or self rather than against foreign antigens (infection). In the present study, phenotypic and functional immunoassays were used in order to investigate whether T-cells in BPH are indeed activated, and whether this activation is systemic or restricted locally to the prostate. Analysis of T-cell activation marker expression and proliferation requirements provided substantial evidence that these infiltrating lymphocytes, in contrast to their peripheral counterparts, are chronically activated. Since local accumulation of activated lymphocytes can cause tissue destruction, high concentrations of cytokines, and consequently tissue rebuilding, this process might contribute to the pathogenesis of BPH.

White pulp reconstitution after human bone marrow transplantation

To reveal the reconstitution process of the white pulp after bone marrow transplantation (BMT), spleens of 24 marrow recipients whose survival times ranged from 34 to 303 days after BMT, were analyzed at the histopathological and immunohistochemical level. Up to 3 months after BMT, the white pulp was atrophic and consisted mainly of T cells forming periarteriolar lymphatic sheaths (PALS). Approximately 100 days after BMT, B cells aggregated in some of the white pulp, forming primary follicles, whereas marginal zones could not be detected. Beyond 4 months after BMT, the PALS, the lymphoid follicle, and the marginal zone of the white pulp could be seen in most of the recipients' spleens. However, the recovery of the marginal zone was poor up to 10 months after BMT. Thus, the white pulp was reconstituted sequentially, beginning in the PALS, followed by reconstitution in lymphoid follicles, and finally in the marginal zone. The development of the PALS corresponded well with the appearance of interdigitating dendritic cell, as did the development of lymphoid follicles with the appearance of follicular dendritic cell. The sequential reconstitution of the white pulp demonstrated in this study provides the morphological basis for the functional immune recovery of marrow recipients. In particular, the delay of the marginal zone reconstitution seems to be responsible for the functional asplenia of long-term survivors.

The conjunctiva in acute and chronic mucous membrane pemphigoid. An immunohistochemical analysis

BACKGROUND

The mechanism of chronic progressive conjunctival cicatrization in mucous membrane pemphigoid is not well understood, and current therapy is often of limited use. Rapid progression of cicatrization follows exacerbations of clinical inflammation, and the investigation of immune mechanisms related to disease activity may provide a clue for more effective therapeutic strategies.

METHODS

The authors undertook an immunohistochemical study, using monoclonal and polyclonal antibodies in glycol methacrylate-embedded tissues, of epibulbar conjunctival biopsy specimens obtained from 20 patients with ocular cicatricial pemphigoid and from 12 matched healthy controls. The study patients were classified according to the ocular disease activity as acute ulcerative (n = 4), subacute (n = 8), and chronic (n = 8).

RESULTS

The composition of the subepithelial cellular infiltrate varied with disease activity. Acute disease was characterized by an abundance of macrophages and neutrophils. The number of T lymphocytes was significantly raised in all the disease groups, but were most marked in subacute disease. Of the T-cell subsets, there were more CD8- than CD4-positive cells observed, except in acute disease where there were equal numbers. Only approximately 5% of the T cells in all disease groups were activated as demonstrated by expression of interleukin-2 receptor. There was increased expression of major histocompatibility complex class II (MHC II) molecules on macrophages, fibroblasts, and other cells in all the groups. The number of B cells and natural killer cells was not increased. Staining for the fibrogenic cytokines, transforming growth factor-beta (TGF-beta), platelet-derived growth factor, and basic fibroblast growth factor was found in both pemphigoid patients and control persons, but the intensity of TGF-beta staining was significantly greater in acute disease.

CONCLUSIONS

The composition of the cellular infiltrate in the bulbar conjunctiva depends on clinical disease activity. The numbers of neutrophils and macrophages seem to reflect clinical disease activity. Fibrogenic cytokines, especially TGF-beta, may play an important role in the formation of conjunctival scar tissue.

Cytomegalovirus- and interferon-related effects on human endothelial cells. Cytomegalovirus infection reduces upregulation of HLA class II antigen expression after treatment with interferon-gamma

Cultured human umbilical vein endothelial cells (HUVEs) were infected with human cytomegalovirus (HCMV) strain AD169. Up to 50% HUVEs proved to be positive for HCMV early nuclear antigens 24 hours after inoculation with virus. Following infection kinetics of surface expression of HLA class I and II, intercellular adhesion molecule (ICAM-1) and endothelial lymphocyte adhesion molecule (ELAM-1) on HUVEs were investigated by means of flow cytometry. A slight increase in HLA class I expression was observed, whereas expression of HLA class II (DR, DP, DQ) antigens was not induced by infection with HCMV. Furthermore, when compared with uninfected cells treated with interferon-gamma (IFN-gamma), reduced enhancement of HLA-DR expression was conspicuous in HCMV-infected cells treated with IFN-gamma. There is evidence that only a portion of HUVE is affected in its ability to upregulate HLA class II antigens. While expression of ICAM-1 was found to be enhanced between 8 and 20 hours after infection with a maximum at 12 hours after infection, no modulation of ELAM-1 was seen.

Immunohistological and electron microscopical study of nodular fasciitis of the orbit

We report the case of a 7-year-old Japanese girl with nodular fasciitis which was investigated by immunohistological and electron microscopical methods. An excised nodular lesion in her right orbit showed characteristic histological features of the disease. The fibroblastic cells showed myofibroblastic characteristics, such as immunohistochemically positive reactions against muscle specific actin and vimentin and characteristic electron microscopical appearances. The multinuclear giant cells did not react against any histiocytic markers, including HLA-DR, antimacrophage antigen, lysozyme, and S-100 protein, but the myofibroblastic markers and the electron microscopical study did reveal myofibroblastic characters.

Immunocytochemical observations on macrophage populations in normal fetal and adult human liver

Phenotypic expression of macrophages was studied immunocytochemically in 25 human fetal livers at various stages of development and in 20 normal human adult livers. A panel of commercially available polyclonal and monoclonal antibodies (KP1, Mac387, LN3, CR3/43, and antibodies against muramidase, alpha-1-antitrypsin, and factor XIIIa) was applied to paraffin sections. From the seventh week of gestation macrophages in the fetal liver showed differences in distribution with the various antibodies. Macrophages in adult liver similarly varied in morphology and phenotypic expression. In the light of these results, we conclude that the population of human liver macrophages is heterogeneous from an early stage of fetal development and that this heterogeneity extends into adult life.

Morphological and immunohistological study of testicular lymphomas

We have studied normal testis, seminomas and malignant lymphomas of the testis using routine stains and a panel of antibodies directed against lymphoid and basement membrane antigens. The results show that normal testis contains, at most, a minor population of T-lymphocytes: seminomas contain mixed T- and B-cell populations with a predominance of B-lymphocytes; and most primary lymphomas are B-cell tumours of large centroblastic type. Solid testicular lymphomas presenting secondarily to acute lymphoblastic leukaemias showed intact seminiferous tubular basement membranes with predominantly interstitial lymphomatous infiltrates, whereas the tubules in primary cases were over-run by lymphoma cells and basement membranes were disrupted.

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-D region alpha-chain monoclonal antibodies: cross-reaction between an anti-DP alpha-chain antibody and smooth muscle

Two monoclonal antibodies, Tal 3C3 and Tal 1B5, raised against purified plasma membrane extract of the Bristol 8 B lymphoblastoid cell line and previously shown to recognize epitopes on denatured HLA-D alpha-chains revealed several differences in staining patterns when screened by immunocytochemical techniques on pre-fixed paraffin-embedded sections of human tissues. Although Tal 3C3 staining was weaker and more restricted than Tal 1B5 on immunoregulatory cells expected to express class II antigens, this monoclonal antibody showed additional strong activity on normal smooth muscle. Biochemical studies show that whereas Tal 1B5 reacts with DR alpha-chains, Tal 3C3 predominantly defines DP alpha-chain subunits and a high molecular weight (200-250 kD) actin binding protein known as filamin. In view of several recent reports that the cellular distribution of class II antigens may be more widespread than hitherto thought and may be expressed by cells not normally involved in specific immune functions, these findings emphasize that unexpected monoclonal antibody reactions must be interpreted with caution. It is clearly important to include both immunohistological tissue section and biochemical studies in the initial screening procedures for monoclonal antibodies in order to distinguish between specific target antigen activity and cross-reactions with unrelated molecules.

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.

Ploidy, proliferative activity, cluster differentiation antigen expression and clinical remission in high-grade non-Hodgkin's lymphoma

Using a large range of monoclonal antibodies to specific cluster differentiation antigens the phenotypes of a series of high-grade non-Hodgkin's lymphomas of B- and T-cell type were investigated. Cell ploidy and proliferative fraction were assessed by fluorescent staining of DNA and flow cytometry and data on the incidence of complete clinical remission were obtained. With the exception of some lymphoblastic lymphomas, high-grade B-cell lymphomas normally expressed the pan B-cell antigens CD19 and CD22 but only immunoblastic lymphomas consistently expressed the pan B marker CD20. Variable, generally weak expression of CD21 was observed whilst CD23 expression was most prevalent in rapidly proliferative cases and in Burkitt's and centroblastic lymphomas. A rapidly proliferative, multilobated B-cell lymphoma displayed phenotypic properties intermediate between centroblastic and immunoblastic lymphomas. The T-cell lymphomas generally showed low proliferative activity and expression of CD4 prevailed over CD8. Most cases also showed CD2 and CD5 positivity with some also showing CD3 and CD7 expression. Patients with rapidly proliferative diploid or DNA aneuploid tumours obtained complete remission more readily than patients with lowly proliferative diploid tumours. An excess of early deaths occurred among T-cell cases.