Activation pathways of synovial T lymphocytes. Expression and function of the UM4D4/CDw60 antigen

Cell cycle arrest and apoptosis induced by O-acetyl-GD2-specific monoclonal antibody 8B6 inhibits tumor growth in vitro and in vivo

O-Acetyl-GD2 ganglioside is suitable antigen for tumor immunotherapy with specific therapeutic antibody. Here, we investigate the anti-tumor activity of O-acetyl-GD2-specific monoclonal antibody 8B6 on O-acetyl-GD2-positive tumor cells. The results indicated that mAb 8B6 induced growth inhibition of O-acetyl-GD2-expressing tumor cell lines in vitro with features of cell cycle arrest and apoptosis. Monoclonal antibody 8B6 treatment was also very effective in suppression of tumor growth in mice by reducing the proliferation index and increasing the apoptotic index. Such a study represents a useful framework to optimize immunotherapy with O-acetyl-GD2-specific antibody in combination with chemotherapeutic agents.

Differential surface expression and possible function of 9-O- and 7-O-acetylated GD3 (CD60 b and c) during activation and apoptosis of human tonsillar B and T lymphocytes

The disialoganglioside GD3 (CD60 a) and its O-acetylated variants have previously been described as surface molecules of human T lymphocytes of the peripheral blood system. Here we report the expression of the 9-O-, and 7-O-acetylated disialoglycans of GD3 (CD60 b and CD60 c respectively) on human tonsillar lymphocytes. CD60 b and c are surface-expressed on activated germinal centre B cells and colocalize in raft-like structures on the cell surface together with the cytoplasmic tyrosine kinase Lyn and Syk. Addition of CD60 b and c mAb together with anti-IgM/IL-4 to in vitro cultivated tonsillar B cells resulted in a costimulatory effect. During spontaneous and staurosporine-induced apoptosis a distinct population of activated annexin V+/CD60 b+/CD60 c- B cells was observed. CD60 b and c are also found on cells of the extrafollicular T cell area. On tonsillar T cells, CD60 b mAb had a costimulatory effect together with PHA while CD60 c mAb alone was sufficient to induce proliferation. In further contrast to B cells, during apoptosis a distinct CD60 b+ T cell subpopulation was not observed. Together, surface-expressed CD60 b and c are differently expressed on tonsillar B and T cells and may be involved in the regulation of activation and apoptosis of lymphocytes in secondary lymphatic tissue.

Synovial fibroblasts and synovial macrophages from patients with rheumatoid arthritis and other inflammatory joint diseases show chromosomal aberrations

Chromosomal aberrations were investigated in nuclei extracted from synovial tissue and first-passage synovial fibroblasts (P-1 SFB, 98% enrichment) or macrophages (P-1 Mphi) from patients with rheumatoid arthritis (n=10). The findings were compared with those in other rheumatic diseases (osteoarthritis, n=14; reactive arthritis, n=1), as well as with those in chronic obstructive pulmonary disease (n=8). Controls were paired peripheral blood lymphocytes from arthritic patients, synovial tissue or SFB/Mphi from joint trauma/normals (n=9), and peripheral blood monocytes from normal donors (n=10). GTG banding of metaphase chromosomes and interphase fluorescence in situ hybridization with centromere-specific probes were used. Comparable chromosomal aberrations were observed in synovial tissue and P-1 SFB of patients with rheumatoid arthritis, osteoarthritis, and reactive arthritis (polysomy 7 and aneusomies of chromosomes 4, 8, 9, 12, and 18). Notably, aneusomies of chromosomes 4, 6, 7, 8, 9, 11, 12, and/or X were also detected in P-1 synovial Mphi from rheumatoid arthritis (90% of the cases), osteoarthritis (93%), and reactive arthritis (1/1), as well as bronchial Mphi from chronic obstructive pulmonary disease (25%). No aberrations were detected in paired peripheral blood lymphocytes (except for one osteoarthritis case with a karyotype 45,X[10]/46,XX[17]), or in peripheral blood monocytes and synovial tissue of normals/joint trauma. Because Mphi aberrations were common to chronic joint and pulmonary disease, chronic inflammatory stress may induce chromosomal aberrations with potential functional relevance in local mesenchymal cells and infiltrating leukocytes in an organ-independent fashion.

Expression of the dendritic cell-associated C-type lectin DC-SIGN by inflammatory matrix metalloproteinase-producing macrophages in rheumatoid arthritis synovium and interaction with intercellular adhesion molecule 3-positive T cells

OBJECTIVE

To determine whether matrix metalloproteinase (MMP)-producing inflammatory macrophages in the synovium of rheumatoid arthritis (RA) patients express the novel dendritic cell (DC)-specific C-type lectin DC-SIGN and whether this expression is associated with the presence of naive T cells expressing the DC-SIGN ligand, intercellular adhesion molecule 3 (ICAM-3).

METHODS

Reverse transcription-polymerase chain reaction was performed to study the expression of DC-SIGN in synovium samples from RA, osteoarthritis (OA), and trauma patients. DC-SIGN expression on RA monocytes or on monocytes stimulated with granulocyte-macrophage colony-stimulating factor and interleukin-4 was further investigated by flow cytometry. To localize DC-SIGN in the synovium, the DC markers ICAM-3 and MMP-1 were analyzed by immunohistochemistry (single and double labeling) on serial cryostat sections.

RESULTS

Seventy percent of the inflammatory cells in the synovium of RA patients showed high expression of DC-SIGN. DC-SIGN was expressed by 80% of CD68-positive macrophages, but not by CD83-positive, DC-LAMP-positive, or Fascin-positive cells. Normal numbers of DC-SIGN-positive cells were found in the peripheral blood of RA patients, suggesting that DC-SIGN is up-regulated locally in the joint. In RA synovium, ICAM-3-positive resting T cells were found in close proximity to DC-SIGN cells. Unexpectedly, a lower percentage of DC-SIGN-expressing cells was found in OA synovium compared with RA synovium. Furthermore, ICAM-3-expressing T cells, which are known to bind DC-SIGN, were almost absent within the synovium of OA and trauma patients. DC-SIGN-positive macrophages adjacent to these T cells were located in close proximity to the cartilage-degrading proteins extracellular MMP inducer (EMMPRIN) and MMP-1.

CONCLUSION

The C-type lectin DC-SIGN is almost absent in the synovium of trauma patients but is highly expressed by most CD68-positive macrophages in the synovium of RA patients. The lack of correlation between DC-SIGN expression and the expression of CD83, DC-LAMP, or Fascin indicates that multiple DC/macrophage subsets are present in RA synovium. Expression of DC-SIGN and its ligand, ICAM-3, is found in substantial amounts only in RA synovium, suggesting that their interaction is implicated in the additional activation of synovial macrophages that leads to the production of EMMPRIN and MMP-1.

In vivo activated T cells in rheumatoid synovitis. Analysis of Th1- and Th2-type cytokine production at clonal level in different stages of disease

T-cell cytokines play a crucial role in the pathogenesis and progression of rheumatoid arthritis (RA). Their detection in the joint, however, is impaired by the complex network present in the synovium. Although many synovial T cells show signs of previous activation, only a few express interleukin (IL)-2 receptor, marker of recent activation. The aim of this study was to analyse the cytokine production by in vivo activated (IL-2R +) T cells from RA at different stages of the disease. For this purpose, T cells were isolated from peripheral blood and synovial fluid of four patients with active RA, two at the onset of the disease, one in the early phase during treatment, one in long-lasting chronic phase. One patient was studied at the onset of the disease and 52 months later. Cells were initially expanded with a low dose of IL-2, cloned and analysed for cytokine production. The results showed a strong predominance of T helper (Th) 1 clones in the blood and a slight prevalence of Th0 clones in the joint of all the four patients. Interferon-gamma and IL-2 production was higher in the long-lasting RA, whereas IL-4 synthesis was prevalent in early RA. Enrichment in IL-10-producing clones was present only in the joint of the untreated patients. The longitudinal study confirmed the differences in cytokine production between early and late phases of disease. These data confirm that RA is mainly a Th1-driven condition. However, in vivo activated synovial T cells produce also Th2-type anti-inflammatory cytokines, such as IL-4 and IL-10. The synthesis of both cytokines is a feature of the very early phase of RA, although the selective recruitment of IL-10-producing T cells is quickly lost.

The T lymphocyte structure CD60 contains a sialylated carbohydrate epitope that is expressed on both gangliosides and glycoproteins

The CD60 antigen is expressed on a majority of T cells in autoimmune lesions, and anti-CD60 can activate T lymphocytes. CD60 has been defined as the GD3 ganglioside, and subsequently as the 9-O-acetylated form of GD3. However, other evidence suggests that anti-CD60 recognizes a glycoprotein or family of glycoproteins expressed by T lymphocytes. The current studies were undertaken to better define the identity of the CD60 antigen on both T cells and non-T cells. Treatment of intact cells with neuraminidases of various specificities confirmed that detection of the CD60 epitope depends on expression of an alpha2, 8-disialic acid carbohydrate linkage, as is found in GD3 and related gangliosides. However, the sialicacid polymer colominic acid inhibited anti-GD2 and anti-GD3, but not anti-CD60 from binding to cell surfaces. Expression of CD60 did not correlate with expression of GD3 on a variety of cell lines and T cell populations. Expression of CD60 and 9-O-acetyl-GD3 was roughly parallel on some non-T cell lines such as melanoma cells, but on T cells expression of CD60 was consistently greater. Antibodies to GD2, GD3 and 9-O-acetyl-GD3 were ineffective at inhibiting binding of anti-CD60 to CD60+ cells. Activation responses of T cells to anti-CD60 were inducible in either the presence or absence of a response to anti-GD3. A novel inhibitor of glucosyl ceramide synthesis, D-threo-1-phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (D-t-P4) reduced expression of GD3 much more than CD60 on activated T lymphocytes. Following biotinylation of HUT78 T cells, anti-CD60 immunoprecipitated a 70 kDa antigen. Taken together, the present data and previous findings suggest that anti-CD60 can recognize both a modified form of the GD3 ganglioside and a carbohydrate-dependent complex epitope present on one or more glycoproteins. This glycoprotein epitope may be the more abundant and functionally significant CD60 antigen on T lymphocytes, while 9-O-acetyl-GD3 is likely to be the principal structure recognized by anti-CD60 on melanoma cells. These findings emphasize the complexity of understanding the functional roles of carbohydrate epitopes in cell activation.

Keratinocyte CDw60 expression is modulated by both a Th-1 type cytokine IFN-gamma and Th-2 cytokines IL-4 and IL-13: relevance to psoriasis

SUMMARY

Psoriasis is a chronic skin disease with an immunocytic infiltrate, including activated T lymphocytes, producing multiple cytokines that can influence the phenotype of epidermal keratinocytes. In these studies we examined the effect of the cytokines interferon-gamma and interleukin-13 or interleukin-4 on keratinocytes, alone and in combination, on surface levels of HLA-DR, intercellular adhesion molecule 1, and CDw60, as well as the transcription factors STAT1, STAT6, and BCL-6. As CDw60 is an acetylated form of the GD3 ganglioside and may function as a T cell costimulatory molecule, the modulation of CDw60 expression by keratinocytes in psoriatic lesions was highlighted to gain insight into potentially important T cell-keratinocyte interactions. Interferon-gamma was observed to block the interleukin-4- or interleukin-13-mediated induction of CDw60 on cultured keratinocytes, but not induction of the transcription factor STAT6. Interleukin-13 and interleukin-4 were unable to block interferon-gamma-mediated induction of STAT1 or BCL-6, however, or the upregulation of intercellular adhesion molecule 1 and HLA-DR. In psoriatic plaques, CDw60 was not consistently detected on keratinocytes in acute lesions, but was detected predominantly on basal layer keratinocytes in chronic lesions. In addition we found that BCL-6 levels were increased in psoriatic lesions; in acute lesions BCL-6 was primarily localized in the basal layer keratinocytes, whereas in chronic plaques nuclear BCL-6 was predominantly expressed by keratinocytes in the suprabasal cell layers. These studies highlight the complex modulation of the keratinocyte phenotype by immunocyte-derived cytokines, in which induction of CDw60 involving interleukin-4, or interleukin-13 was antagonized by interferon-gamma. We suggest in psoriatic plaques that the presence or absence of CDw60 expression by keratinocytes may reflect the dynamic interplay between Th-1-type cytokines such as interferon-gamma and Th-2-type cytokines such as interleukin-4 and interleukin-13. The ability of interferon-gamma to induce the transcription repressor BCL-6 may also contribute to the overall immunologic events in skin, including suppression of the intermediates in the synthetic pathway leading to expression of the T cell costimulatory ganglioside CDw60.

Recognition of cell surface GD3 by monoclonal antibody anti-6C2 in rheumatoid arthritis synovial fluid: expression on human T cells with transendothelial migratory activity

OBJECTIVE

We have previously reported that the anti-6C2 monoclonal antibody (mAb) defines a subset of human CD4+ memory T cells. The present study sought to determine the nature of the 6C2 molecule and the function associated with 6C2+ T cells, and to examine whether this T cell subset is involved in the pathophysiology of rheumatoid arthritis (RA).

METHODS

Cytofluorographic analysis was performed for identification of T cell surface molecules displaying a distribution similar to that of the 6C2 molecule. T cells in the synovial fluid of RA patients were examined for expression of the 6C2 molecule. Transendothelial migratory activity was assessed by assay using monolayers of human endothelial cells. Specific reactivity of the anti-6C2 mAb was determined by immunoblotting on gangliosides separated by thin-layer chromatography, and flow cytometric analysis of the cells transfected with complementary DNA (cDNA) was performed for determination of the glycosyltransferases involved in biosynthesis of the gangliosides.

RESULTS

On human peripheral T cells, the 6C2 molecule was distributed, by and large, in a pattern similar to that of CDw60, or O-acetyl-GD3. The majority (>70%) of synovial fluid T cells from patients with RA were found to be 6C2 positive, and those 6C2+ T cells exhibited a transendothelial migratory capacity that was inhibited by pretreatment of T cells with anti-6C2 mAb. Moreover, treatment of T cells with neuraminidase resulted in a loss of 6C2 expression as well as a reduction in the transendothelial migratory activity. Anti-6C2 mAb reacted specifically with GD3, but not with O-acetyl-GD3. The reactivity of anti-6C2 mAb was induced on the cell surface only by transfection with cDNA for GD3 synthase.

CONCLUSION

The 6C2 molecule is a disialoganglioside, GD3, and is present on a subset of T cells with transendothelial migratory capacity. The 6C2/GD3 molecules, as well as 6C2/GD3+ T cells, appear to play a role in T cell migration and in the inflammation of RA.

Isolation and characterization of rheumatoid arthritis synovial fibroblasts from primary culture--primary culture cells markedly differ from fourth-passage cells

To reduce culture artifacts by conventional repeated passaging and long-term culture in vitro, the isolation of synovial fibroblasts (SFB) was attempted from rheumatoid arthritis (RA) synovial membranes by trypsin/collagenase digest, short-term in vitro adherence (7 days), and negative isolation using magnetobead-coupled anti-CD14 monoclonal antibodies. This method yielded highly enriched SFB (85% prolyl-4-hydroxylase+/74% Thy-1/CD90+ cells; <2% contaminating macrophages; <1% leukocytes/endothelial cells) that, in comparison with conventional fourth-passage RA-SFB, showed a markedly different phenotype and significantly lower proliferation rates upon stimulation with platelet-derived growth factor and IL-1beta. This isolation method is simple and reliable, and may yield cells with features closer to the in vivo configuration of RA-SFB by avoiding extended in vitro culture.

Mosaic chromosomal aberrations in synovial fibroblasts of patients with rheumatoid arthritis, osteoarthritis, and other inflammatory joint diseases

Chromosomal aberrations were comparatively assessed in nuclei extracted from synovial tissue, primary-culture (P-0) synovial cells, and early-passage synovial fibroblasts (SFB; 98% enrichment; P-1, P-4 [passage 1, passage 4]) from patients with rheumatoid arthritis (RA; n = 21), osteoarthritis (OA; n = 24), and other rheumatic diseases. Peripheral blood lymphocytes (PBL) and skin fibroblasts (FB) (P-1, P-4) from the same patients, as well as SFB from normal joints and patients with joint trauma (JT) (n = 4), were used as controls. Analyses proceeded by standard GTG-banding and interphase centromere fluorescence in situ hybridization. Structural chromosomal aberrations were observed in SFB (P-1 or P-4) from 4 of 21 RA patients (19%), with involvement of chromosome 1 [e.g. del(1)(q12)] in 3 of 4 cases. In 10 of the 21 RA cases (48%), polysomy 7 was observed in P-1 SFB. In addition, aneusomies of chromosomes 4, 6, 8, 9, 12, 18, and Y were present. The percentage of polysomies was increased in P-4. Similar chromosomal aberrations were detected in SFB of OA and spondylarthropathy patients. No aberrations were detected in i) PBL or skin FB from the same patients (except for one OA patient with a karyotype 45,X[10]/46,XX[17] in PBL and variable polysomies in long-term culture skin FB); or ii) synovial tissue and/or P-1 SFB of normal joints or of patients with joint trauma. In conclusion, qualitatively comparable chromosomal aberrations were observed in synovial tissue and early-passage SFB of patients with RA, OA, and other inflammatory joint diseases. Thus, although of possible functional relevance for the pathologic role of SFB in RA, these alterations probably reflect a common response to chronic inflammatory stress in rheumatic diseases.

Immunocytochemical localization of CDw60 antigens on human peripheral T cells

About 25-35% of human T cells display the CDw60 ganglioside (9-O-acetyl-GD3) antigen at the cell surface [E.P. Rieber, in W. Knapp, B. Dörken, W.R. Gilks, E.P. Rieber, R.E. Schmidt, H. Stein, A.E.G.K. von dem Borne (Eds.), Leucocyte Typing IV, Oxford University, Oxford, 1989, p. 361.]. Other leucocytes do not express this antigen on the cell surface. This led us to investigate its presence by flow cytometry and immunoelectron microscopy (IEM). Flow cytometric analysis of isolated peripheral T cells showed 26% of the cell population to have the CDw60 antigen expressed on the cell surface whereas 74% did not. Similarly, IEM analysis of 262 random T cells by the preembedding immunogold labeling technique revealed CDw60 surface expression to be tetrapartite: (a) the majority of 63.7% of the T cells did not show any surface associated gold label; (b) 19.5% were of low CDw60 surface exposition, corresponding to a linear density of 0.05-2.0 gold markers per microm; (c) about 13.4% showed a medium surface exposition with a linear density of 2.1-4.5 gold markers per microm; and (d) a high exposition, ranging from 4.6 to 9.0 gold markers per microm, was seen at 3.4% of the T cells. From postembedding label experiments, which additionally make access to the antigen localized within the cytoplasm, it was found that nearly all T cells contained low levels of intracellular CDw60. Most of it was found to be associated with the cytoplasmic membrane or vesicles, derived from the Golgi. Immunogold conjugates associated with the cytoplasmic membrane showed a linear density up to 0.6 gold markers per microm. The asymmetric expression of the CDw60 antigen on human T cells and its occurrence in nearly all T cells suggests that its surface presentation is tightly regulated.

CDw60: an antigen expressed in many normal tissues and in some tumours

CDw60 is a recently described T-cell antigen, which functionally delivers a costimulatory signal in T-cell activation. In addition, CDw60 has been regarded as a melanoma-associated antigen. To date, only limited information exists on the distribution of CDw60 in other normal and pathologically altered tissues in human. In the present study, the expression of CDw60 was analysed immunohistologically in a large panel of formalin-fixed and paraffin-embedded normal and pathological human tissues. The antigen was detected in several normal tissues, such as epithelia of the reproductive system, exocrine and endocrine glands, glial cells and neurons of the central and peripheral nervous systems, and lymphoid cells. These showed different subcellular distribution patterns, i.e. (1) cell surface labelling of peripheral lymphocytes and lymphocytes of the lymph node and thymus, (2) diffuse cytosolic staining in lymphocytes, subpial glial processes, and the outer plexiform layer of the retina, (3) granular cytoplasmic staining associated with the Golgi apparatus in epithelial cells of certain endocrine and exocrine glands, of the ductus epididymis and deferens, neurons of the peripheral and central nervous system, and lymphocytes and megakaryocytes of the bone marrow. In exocrine glands, e.g. of the prostate and uterine corpus, CDw60-positive Golgi fields were located in the juxtaluminal cell compartment, thus reflecting a polarized distribution. In some malignant tumours, the neoplastic cells contained CDw60-immunolabelled Golgi complexes, which were disorderly distributed throughout the cytoplasm, thus reflecting a loss of epithelial polarity. Only in mammary carcinomas was abnormal cell surface labelling detected. A putative de novo expression of CDw60 was observed in pleomorphic adenoma and mucoepidermoid carcinoma of the parotid gland, seminoma, embryonal and teratocarcinoma of the testis, small cell carcinoma of the lung, and malignant melanoma. These results define the CDw60 determinant as a broadly distributed antigen within a large panel of normal human tissues. The antigen is also detectable in some previously undescribed benign and malignant tumours, which may give importance to CDw60 as a possible diagnostic marker.

CD30+ T cells in rheumatoid synovitis: mechanisms of recruitment and functional role

High serum levels of soluble CD30 (sCD30) have been reported to better predict the response to second line therapy in rheumatoid arthritis (RA). It is believed that sCD30 is released by CD30+ T cells present in the RA synovium. However, both the mechanism of recruitment to the joint and the functional role of this T cell subset in the pathogenesis of the disease remain unknown. This study confirmed higher levels of sCD30 in the serum and synovial fluid (SF) of RA patients compared with normal controls. However, analysis of mRNA and cell surface CD30 expression showed that CD30+ T cells are detectable in the SF, but not in the synovial membrane. In contrast, T cells expressing the CD30 transcript, but not the surface molecule, were found in the peripheral blood of both RA and normal controls. CD30 surface expression was up-regulated by adhesion and migration through endothelium in vitro and in a delayed-type hypersensitivity model in vivo. Although the great majority of fresh or cloned CD30+ T cells from SF produced both IFN-gamma and IL-4, CD30 expression strictly correlated with IL-4 synthesis in synovial T cell clones. In addition, CD30+ T cell clones also produced high amounts of the anti-inflammatory cytokine IL-10. On this basis, we would like to propose that synovial CD30+ cells may play a role in the control of the inflammatory response. Serum sCD30 may reflect such cell activity and, therefore, explain the previously demonstrated correlation between high sCD30 serum levels and positive response to therapy.

Developmental changes and functional properties of human memory T cell subpopulations defined by CD60 expression

The present study was undertaken to examine developmental changes of T cells expressing CD60 and their functional properties. Three-color immunofluorescence analysis revealed that the CD60 antigen was preferentially expressed on a proportion of memory (CD45RO+) CD4+ T cells, but less on memory CD8+ T cells, while this antigen is undetectable in naive (CD45RO-) T cells. A frequency of memory CD4+ T cells expressing CD60 in the peripheral blood was negligible in newborns and gradually increased with advancing age. CD60+ memory CD4+ T cells showed stronger proliferative responses to PPD and produced higher levels of IL-4 and IL-10 than CD60- ones, whereas production of IL-2 and IFN-gamma was similarly found in both cell subpopulations. In addition, it was shown that efficient helper activity for Ig production by B cells was predominated in CD60+ memory CD4+ T cells. These results suggest that CD60 may be primarily expressed on the functionally differentiated memory effector cells among circulating CD45RO+ CD4+ T cells.

The 9-O-acetylated disialosyl carbohydrate sequence of CDw60 is a marker on activated human B lymphocytes

Gangliosides with a terminal 9-O-acetylated disialosyl group (CDw60 structures) show a restricted surface expression on human leukocytes. Hithereto, they have only been detected on subpopulations of human T lymphocytes. Using the defined CDw60 antibody UM4D4 and two new antibodies with preferential CDw60 activities, F6 and Z17, we demonstrate for the first time that CDw60 is an activation marker on human B lymphocytes. In vitro phorbol ester-stimulated human peripheral blood B lymphocytes as well as in vivo activated tonsillar B lymphocytes became CDw60 positive. CDw60 expression of these cells exceeds that of resting and activated T-lymphocytes.

9-O-Acetylation of sialomucins: a novel marker of murine CD4 T cells that is regulated during maturation and activation

Terminal sialic acids on cell surface glycoconjugates can carry 9-O-acetyl esters. For technical reasons, it has previously been difficult to determine their precise distribution on different cell types. Using a recombinant soluble form of the Influenza C virus hemagglutinin-esterase as a probe for 9-O-acetylated sialic acids, we demonstrate here their preferential expression on the CD4 T cell lineage in normal B10.A mouse lymphoid organs. Of total thymocytes, 8-10% carry 9-O-acetylation; the great majority of these are the more mature PNA-, HSA-, and TCRhi medullary cells. While low levels of 9-O-acetylation are seen on some CD4/CD8 double positive (DP) and CD8 single positive (SP) cells, high levels are present primarily on 80- 85% of CD4 SP cells. Correlation with CD4 and CD8 levels suggests that 9-O-acetylation appears as an early differentiation marker as cells mature from the DP to the CD4 SP phenotype. This high degree of 9-O-acetylation is also present on 90-95% of peripheral spleen and lymph node CD4 T cells. In contrast, only a small minority of CD8 T cells and B cells show such levels of 9-O-acetylation. Among mature peripheral CD4 T lymphocytes, the highly O-acetylated cells are Mel 14(hi), CD44(lo), and CD45R(exon B)hi, features typical of naive cells. Digestions with trypsin and O-sialoglycoprotease (OSGPase) and ELISA studies of lipid extracts indicate that the 9-O-acetylated sialic acids on peripheral CD4 T cells are predominantly on O-linked mucintype glycoproteins and to a lesser degree, on sialylated glycolipids (gangliosides). In contrast, sialic acids on mucin type molecules of CD8 T cells are not O-acetylated; instead these molecules mask the recognition of O-acetylated gangliosides that seem to be present at similar levels as on CD4 cells. The 9-O-acetylated gangliosides on mouse T cells are not bound by CD60 antibodies, which recognize O-acetylated gangliosides in human T cells. Tethering 9-O-acetylated mucins with the Influenza C probe with or without secondary cross-linking did not cause activation of CD4 T cells. However, activation by other stimuli including TCR ligation is associated with a substantial decrease in surface 9-O-acetylation, primarily in the mucin glycoprotein component. Thus, 9-O-acetylation of sialic acids on cell surface mucins is a novel marker on CD4 T cells that appears on maturation and is modulated downwards upon activation.

Rheumatoid arthritis as a bone marrow disorder

Both the concept of rheumatoid arthritis (RA) as an autoimmune process restricted to joints and the major role of T cells in its pathogenesis have been challenged in the literature. Fibroblastlike and macrophagelike synoviocytes play an important role in RA pannus, and these cells originate in or have their counterpart in bone marrow (BM). Yet the B cell autoimmunity characteristic of RA occurs early, and synovial tissue, like BM, favors the B cell response. Because BM is abnormal in RA, and because germinal centers are unique to RA synovium, RA could be regarded as a disorder of the microenvironments able to sustain B cell response. In fact, RA could even begin in BM, with its onset facilitated by stem cell abnormalities. Moreover, most viruses suspected of playing a role in RA share a BM tropism. This may explain why RA frequently overlaps with other autoimmune disorders and benign lymphoproliferations, such as large granular T lymphocytosis. Because remissions from RA have been reported after BM transplantation, careful studies of the rheumatological outcome of RA patients undergoing such therapeutic procedures are needed. Although RA is a complex process, it can be considered initially as a stem cell disorder requiring treatment similar to that administered to transplant patients. Animal models have provided convincing evidence for these assumptions.

Continuous ambulatory peritoneal dialysis impairs T lymphocyte selection in the peritoneum

Peritoneal lymphocytes (PCL) of 45 healthy individuals, four uremic patients with end-stage renal disease (ESRD) and 25 long-term continuous ambulatory peritoneal dialysis (CAPD) patients were characterized by flow cytometry to investigate whether CAPD alters the phenotype of PCL. B lineage cells constitute a minority of PCL (2.5% of cells). Although the majority of peritoneal T cells expressed alpha beta T cell receptor (TcR), 7% expressed gamma delta TcR, a proportion which was significantly higher than that in peripheral blood (PBMC) (approximately 4%). The majority of PCL T cells exhibited markers of the thymus-dependent lineage (CD2, CD3, TcR alpha beta, CD8 alpha beta or CD4) and surface antigens associated with memory and activation (CD45RO, CD11a, CD18, CD49d, HLA-DR). An average of 75% of both CD4+ and CD8+ PCL T cells of healthy subjects and CAPD patients were CDw60+, thus characterizing the T cell subset containing the helper activity for the mitogen-driven B cell differentiation. CD44s was abundantly expressed on PCL T cells. In contrast to PCL T cells of healthy subjects peritoneal T lymphocytes of CAPD patients exhibited CD44 splice variants containing products of exon-v9 and the proportion of CD44v9+ cells correlated with the frequency of peritonitis episodes the patients had gone through. The majority of PCL T cells of both healthy subjects and CAPD patients were CD8+. A large proportion of CD8+ PCL T cells from healthy subjects expressed the homodimeric CD8 alpha alpha isoform; however, such cells were not found in CAPD patients. In healthy subjects mRNA for the recombination activating gene 1 (RAG-1) was detectable in a PCL population containing CD7-CD34+ and CD7+CD34+ cells. In contrast, neither mRNA transcripts of the RAG-1 gene nor CD34+ cells were detectable in PCL of CAPD patients.

A method for monoclonal antibody isotype switching: anti-CD60 VH expression in a heavy chain-deficient hybridoma variant

Alteration of monoclonal antibody isotype is desirable for a variety of purposes, including obtaining an improved reagent for investigative or therapeutic use. A variety of approaches for isotype switching, particularly from IgM to various IgG subclasses, have been described. Antibodies that recognize carbohydrate determinants on glycoproteins, glycolipids, or polysaccharides are generally of the IgM isotype. This includes all available antibodies to the human CD60 antigen, a determinant with cell coactivating properties described on a subset of T lymphocytes and on other cell types. In this report a new method for monoclonal antibody isotype switching is presented. A plasmid containing the VH regions of anti-CD60 linked to C gamma 1 was transfected into a spontaneously arising variant of the CD60 hybridoma that produced kappa light chain but no heavy chain. This transfected hybridoma line maintains stable production of useful quantities of IgG1 monoclonal anti-CD60 in vitro and in vivo.

CDW60, which identifies the acetylated form of GD3 gangliosides, is strongly expressed in human basal cell carcinoma

The monoclonal antibody UM4D4, assigned to the CDw60 cluster of differentiation, identifies an epitope expressed on a subset of normal T cells, some malignant T cells, melanocytes, malignant melanoma cells and hyperproliferative psoriatic keratinocytes. CDw60 antibodies bind to the acetylated form of GD3 gangliosides. These gangliosides have been implicated in the control of cellular proliferation. Because the acetylated form of GD3 has been demonstrated in basal cell carcinomas, we determined whether the CDw60 epitope was expressed in basal cell carcinomas (n = 24) and squamous cell carcinomas (n = 2). Biopsies of these tumours were sectioned on a cryostat, and stained with anti-CDw60 using a sensitive indirect immunoperoxidase technique. A mean of 74 +/- 4% (mean +/- SEM) of the basal cell carcinoma cells expressed CDw60. In contrast, CDw60 expression in normal skin was confined to melanocytes and a few scattered keratinocytes at the basal cell layer. CDw60 expression in basal cell carcinomas was highly upregulated at the tumour front in most of the lesions, whereas the squamous cell carcinomas showed uniform CDw60 expression in all areas.

Granzyme-positive cytotoxic cells are specifically increased in early rheumatoid synovial tissue

OBJECTIVE

To define the expression and the phenotype of granzyme (Gran) A and B positive cytotoxic cells in synovial tissue (ST) from patients with rheumatoid arthritis (RA) with respect to disease duration and activity.

METHODS

Using antibodies against GranA and GranB, which serve as markers of activated natural killer (NK) cells and cytotoxic T lymphocytes, ST sections from 10 patients with early RA, 10 patients with longstanding RA, and 10 patients with osteoarthritis were examined. The phenotype of Gran+ cells was determined with double-labeling techniques.

RESULTS

Gran+ cells, the majority of which were NK cells, were found in ST from patients in all groups. Several of these cells did not express the surface markers CD16, CD56, and CD57. The highest ST expression of GranB was found in patients with early RA. In RA patients, there was a positive correlation of GranB expression with serum levels of acute-phase reactants, but not with histologic scores for inflammation.

CONCLUSION

Gran+ cells are mainly NK cells, a substantial proportion of which do not express conventional NK cell surface markers. GranB expression is specifically increased in the synovial tissues of patients with RA of short duration.

CDw60: a marker for human CD8+ T helper cells

The existence of helper cells among the CD8+ T cell subset has been recognized for a long time. However, the phenotype of these cells has remained elusive. In this study, we provide evidence that the expression of the CDw60 antigen on human CD8+ T cell allows one to distinguish between CD8+ T helper cells and CD8+ T cells with cytotoxic and suppressor capacity. CDw60 monoclonal antibodies (mAb) recognize the 9-O-acetylated disialosyl group on ganglioside GD3 expressed on 20-40% of CD8+ cells. By use of the direct and indirect mAb-rosetting technique, we were able to isolate the CDw60+CD8+ and CDw60-CD8+ cells at high purity. The alloantigen-specific cytotoxic activity of CD8+ cells resided entirely in the CDw60- population. Helper and suppressor capacity of both CD8 subsets was assayed by the pokeweed mitogen-induced differentiation of B cells into immunoglobulin-secreting cells. These studies clearly indicate that the CDw60+CD8+ subset provided substantial help to B lymphocytes, whereas the CD8+ cells with the CDw60- phenotype were suppressing B cell differentiation. Both subsets produced similar amounts of interleukin 2 (IL-2) after stimulation with phytohemagglutinin. Activation with phorbol myristate acetate in combination with Ca-ionophore induced IL-4 secretion in both populations, but preferentially in the CDw60+ subset, whereas the vast majority of interferon gamma was produced by the CDw60-CD8+ cells. When used in combination with other markers, CDw60 may prove to be useful in defining CD8+ subsets with reciprocal functional activities.

CELL-SURFACE ANTIGENS

The cell surface is covered with protein molecules that are held in the membrane by hydrophobic transmembrane segments or glycosyl–phosphatidylinositol (GPI) anchors. Antigens found on cell surfaces comprise not only those encoded by the cell itself but also the products of intracellular parasites. Soluble ligands may be bound to receptor structures on the cell membrane or lectin-like molecules bound to cell-surface carbohydrate structures. The molecules that form an integral part of the cell surface may be proteins, glycoproteins, or glycolipids. They subserve one of three major functions: adhesion, antigen recognition, or receptors for soluble mediators. However, many cell-surface molecules possess more than one function—for example, molecules involved in cell–cell or cell–extracellular matrix adhesion can also themselves be involved in signal transduction. The cell-surface antigens of leukocytes have been intensively studied because of ease of access to this cellular compartment.

Leukemic T cells from patients with cutaneous T-cell lymphoma demonstrate enhanced activation through CDw60, CD2, and CD28 relative to activation through the T-cell antigen receptor complex

Antigen-dependent activation of T cells occurs through the T-cell antigen-receptor complex (TCR/CD3). Antigen-independent T-cell activation may occur through the surface molecules CDw60, CD2, and CD28. We wished to determine whether these antigen-independent T-cell-activation pathways could be involved in proliferation of leukemic T cells from patients with cutaneous T-cell lymphoma (CTCL). Whereas CDw60 was only expressed on 28% +/- 7% (mean +/- SEM) of blood T cells obtained from healthy control subjects (n = 4), CDw60 was expressed on 94% +/- 3% of blood T cells obtained from patients with CTCL (n = 4). Dual color immunofluorescence microscopy of the T-cell infiltrate in involved skin of these patients demonstrated that almost 100% of the T cells expressed CDw60. Not only did T cells in the patients with CTCL express CDw60, but triggering of the T cells with anti-CDw60 resulted in enhanced proliferation relative to anti-TCR/CD3 and mitogenic lectins. Other antigen-independent pathways also appeared highly active in the T cells from patients with CTCL because enhanced proliferation relative to anti-TCR/CD3 or mitogenic lectins was found when anti-CD2 or anti-CD28 plus phorbol ester was used as stimulant. Despite the brisk proliferation induced by anti-CDw60, anti-CD2, or anti-CD28, T cells from the patients did not produce detectable amounts of gamma-interferon. The inability to produce gamma-interferon correlates with our finding of absent (n = 3) or weak (n = 1) intercellular adhesion molecule-1 expression in the lesional keratinocytes in these patients. In conclusion, T cells of patients with CTCL demonstrate elevated expression of a T-cell-independent signaling molecule CDw60 and respond to antigen-independent activating signals.

Enhanced chondrocyte destruction by lymphokine-activated killer cells. Possible role in rheumatoid arthritis

OBJECTIVE

The lysis of chondrocytes, the parenchymal cells of cartilage, by lymphocytes may provide a potent mechanism by which the immune system participates in sustaining joint damage in rheumatoid arthritis (RA). We studied the capability of lymphocytes from healthy individuals and patients with arthritis to lyse chondrocytes.

METHODS

Peripheral blood mononuclear cells (PMBC) were tested for their ability to lyse chondrocytes in a 51Cr-release assay. Enhancement of the chondrolytic activity was determined by preincubating the cells with T cell growth factor (TCGF) or recombinant interleukin-2 (rIL-2) before cytotoxic testing.

RESULTS

PBMC from healthy individuals possessed a low ability to lyse chondrocytes, whereas cells from the synovial fluid of patients with RA displayed higher chondrolytic activity. In RA, modulating factors must come into play because not all synovial fluid sample cells showed high chondrolytic activity and cells from synovial tissue had little or no lytic action on chondrocytes. Chondrolytic activities of cells from all sources, including PBMC from healthy subjects and patients with arthritis and cells isolated from synovial fluid or from the synovial tissue of RA patients, were greatly increased by incubating the cells with TCGF or rIL-2. In contrast, treatment of chondrocytes with interferon-gamma, which enhances major histocompatibility complex gene expression, decreased the susceptibility of chondrocytes to lysis.

CONCLUSION

These observations suggest a mechanism for joint damage in which the destruction of chondrocytes by lymphocytes is controlled by cytokines released during the inflammatory process in arthritic diseases.

Suppression of chronic antigen-induced arthritis in rats by a monoclonal antibody against the T cell receptor alpha beta

We have investigated a role for T cells in chronic antigen-induced arthritis in rats employing a monoclonal antibody (R73 mAb) against the T cell receptor alpha beta. Treatment with R73 mAb from the time of intra-articular antigenic challenge blocked completely the induction of chronic, but not acute ovalbumin-induced arthritis in sensitized rats. Histologically, treatment-controlled arthritic rats exhibited marked hyperplasia of synovial membrane with pronounced infiltration of inflammatory cells including alpha beta + T cells in the chronic phase of arthritis. In contrast, R73 mAb-treated rats had almost normal joint histology. Treatment with R73 mAb after onset of arthritis was also effective in suppressing the progression of chronic antigen-induced joint inflammation. The preventive and suppressive effects of the mAb on chronic antigen-induced arthritis were associated with marked depletion of alpha beta + T cells in peripheral blood. The DTH but not the humoral response to ovalbumin in sensitized rats was suppressed significantly by R73 mAb. Thus, alpha beta + T cells appear to have a central role in both induction and progression of chronic antigen-induced arthritis.

Can hepatocytes serve as 'activated' immunomodulating cells in the immune response?

During the last few years, there has been a growing evidence that hepatocytes are not merely 'passive' target cells for immunological attack by effector T-cells, but may play a more 'active' role in the initiation and perpetuation of the immune response. Immune modulators released by inflammatory cells at the site of inflammation, as well as the eliciting antigen itself, are able to modulate the phenotype of hepatocytes. This would result in abnormal cytokine production and/or cytokine/receptor expression, as well as active synthesis and display of surface immune 'activation' markers and adhesion molecules, which act as co-stimulatory signals for T-cell activation. These accessory functions involve multiple molecular pathways of cell-cell interactions, which in turn will enable hepatocytes to play a role as 'accessory' cells in both the afferent and efferent arms of the cell-mediated immune response.

The importance of the T cell in initiating and maintaining the chronic synovitis of rheumatoid arthritis

We hope that this short review has produced convincing, although indirect, evidence that in the case of rheumatoid synovitis, the T cell is the conductor of an orchestra playing a tune written by an antigen-presenting cell. The tune develops and becomes modified with time, so that it is difficult to discern with clarity much of the original melody. We believe that it may be possible to substitute a new score that will bring this symphony to a harmonious end. We also strongly believe that this is preferable to augmenting the string section or suppressing the percussion section of the orchestra in the vain hope that in the end harmony can be achieved. The final musical analogy must be the hope that the first page of the score can be found, so that we may discover the main theme, the leitmotif, of the rheumatoid-specific antigenic peptide.