Doppa induces cell death but not differentiation of U937 cells: evidence for the involvement of PKC-beta 1 in the regulation of apoptosis.

Recent reports have claimed that activation of protein kinase C (PKC)-beta is sufficient for both differentiation and apoptosis in promyeloid HL60 cells. Phorbol esters which differentially activate PKC isoenzymes in vitro were used to induce differentiation and apoptosis in U937 cells; TPA and Dopp activate all U937 PKC isoenzymes, except PKC-zeta and Doppa activate only PKC-beta l. At concentrations of Doppa below 50 nM, only PKC-beta l was activated by 2 min and apoptosis was induced, but there was no differentiation of cells towards monocytes. TPA (1-25 nM) and Dopp (5-100 nM) activated PKC-alpha, -beta l and-gamma within 2 min and induced differentiation, but only increased apoptosis at the highest concentrations used. Thus, initial activation of PKC-beta l is insufficient for differentiation of U937 cells, but may lead to the induction of apoptosis.

Changes in protein kinase C isoenzyme expression associated with apoptosis in U937 myelomonocytic cells.

Spontaneously apoptotic U937 cells from exponentially growing cell cultures were enriched on discontinuous Percoll density gradients. Increased PKC-beta and reduced PKC-zeta expression were detected in apoptotic cells by Western blotting. Using confocal microscopy, changes in the level of PKC isoenzymes were confirmed and in addition alterations in the subcellular location of PKC isoenzymes were detected in apoptotic cells compared with nonapoptotic cells. The data indicate that the expression of specific PKC isoenzymes is modulated during apoptosis and that PKC-beta and PKC-zeta may play specific roles in the regulation of the apoptotic program.

Plasma cell populations in labial salivary glands from patients with and without Sjögren's syndrome.

Plasma cells expressing IgG, IgA and IgM were quantified in labial salivary glands from patients with Sjögren's syndrome (n = 25) and compared with glands from patients with a variety of systemic diseases (n = 32) and normal individuals (n = 15). Based on qualitative and quantitative analysis, glands from the systemic disease group were divided into normal histology (n = 24) and non-specific inflammation (n = 8) groups. There were no significant differences in cell densities or Ig class proportions between histologically normal glands from patients and those from normal volunteers. Total immunocyte densities were significantly increased in sialadenitis (P < 0.025) and Sjögren's syndrome (P < 0.001) compared with normal histology glands. In both the sialadenitis and Sjögren's syndrome groups there were significant increases in IgG and IgM cell densities (IgG, P < 0.006; IgM, P < 0.001) and proportions (IgG, P < 0.05; IgM, P < 0.001). There were no significant differences in immunocyte densities or proportions between the sialadenitis and Sjögren's syndrome groups except for a lower percentage proportion of IgA cells in the latter (P < 0.038). In all groups the total and individual Ig-class cell densities showed significant positive correlations with extent of leucocyte infiltration (P < 0.01) and negative correlations between IgA and IgG and/or IgM cell proportions. Analysis of the plasma cell data alone and in combination with quantifiable histological parameters failed to yield specific or sensitive diagnostic information. The results suggest that changes in glandular plasma cell populations in Sjögren's syndrome are non-specific.

Epstein-Barr virus and Hodgkin's disease: transcriptional analysis of virus latency in the malignant cells.

Epstein-Barr virus (EBV) is associated with a number of different human tumors and appears to play different pathogenetic roles in each case. Thus, immunoblastic B cell lymphomas of the immunosuppressed display the full pattern of EBV latent gene expression (expressing Epstein-Barr nuclear antigen [EBNA]1, 2, 3A, 3B, 3C, and -LP, and latent membrane protein [LMP]1, 2A, and 2B), just as do B lymphoblastoid cell lines transformed by the virus in vitro. In contrast, those EBV-associated tumors with a more complex, multistep pathogenesis show more restricted patterns of viral gene expression, limited in Burkitt's lymphoma to EBNA1 only and in nasopharyngeal carcinoma (NPC) to EBNA1 and LMP1, 2A, and 2B. Recent evidence has implicated EBV in the pathogenesis of another lymphoid tumor, Hodgkin's disease (HD), where the malignant Hodgkin's and Reed-Sternberg (HRS) cells are EBV genome positive in up to 50% of cases. Here we extend preliminary results on viral gene expression in HRS cells by adopting polymerase chain reaction-based and in situ hybridization assays capable of detecting specific EBV latent transcripts diagnostic of the different possible forms of EBV latency. We show that the transcriptional program of the virus in HRS cells is similar to that seen in NPC in several respects: (a) selective expression of EBNA1 mRNA from the BamHI F promoter; (b) downregulation of the BamHI C and W promoters and their associated EBNA mRNAs; (c) expression of LMP1 and, in most cases, LMP2A and 2B transcripts; and (d) expression of the "rightward-running" BamHI A transcripts once thought to be unique to NPC. This form of latency, consistently detected in EBV-positive HD irrespective of histological subtype, implies an active role for the virus in the pathogenesis of HD and also suggests that the tumor may remain sensitive to at least certain facets of the EBV-induced cytotoxic T cell response.

Detection of Epstein-Barr virus antigens and DNA in major and minor salivary glands using immunocytochemistry and polymerase chain reaction: possible relationship with Sjogren's syndrome.

This study has investigated the presence of Epstein-Barr virus (EBV) in parotid (n = 12), submandibular (n = 15), and minor salivary glands (n = 25) using immunohistochemical methods for detection of EBV-encoded antigens and the polymerase chain reaction (PCR) for detection of viral DNA. Major salivary glands were from patients without connective tissue disease. Labial glands were from patients with primary Sjogren's syndrome (n = 10), rheumatoid arthritis (n = 8), or from normal individuals (n = 7). None of the glands exhibited specific reactivity for lytic (EA-D, EA-R, VCA) or latent (EBNA-2, LMP) viral antigens. Antibodies to EA-D, when used at 20-50 times their optimal concentration, gave lumenal staining of ducts and acini of all the specimens tested (n = 14), irrespective of the presence (n = 8) or absence (n = 6) of EBV-DNA by PCR. Ductal immunoreactivity for the EBV/C3d (CR2, CD21) receptor was found in 40 per cent of specimens. PCR detected EBV-DNA in 64 per cent submandibular, 46 per cent parotid, and 80 per cent of minor glands. There were no significant differences in the detection of EBV-DNA between specimen/patient groups. Only type A EBV was detected by strain typing PCR. These results indicate that EBV (type A), undetected immunocytochemically, is commonly present at low copy numbers within salivary glands irrespective of a clinical diagnosis of Sjogren's syndrome.

Expression of rheumatoid factor associated cross-reactive idiotopes by glandular B cells in Sjögren's syndrome.

B cell expression of the germline gene-encoded, kappa IIIb-associated, rheumatoid factor (RF) cross-reactive idiotope (CRI) 17-109 and three VHI associated RF CRIs (G6, G8, H1) was investigated immunocytochemically in labial salivary glands from nine patients with primary and six with secondary Sjögren's syndrome, and in inflamed submandibular salivary glands from 10 patients with no history of connective tissue disease. Expression of CRIs by B cell infiltrates in labial glands from patients with primary and secondary Sjögren's syndrome were similar. Lymphoid infiltrates of labial glands from Sjögren's syndrome patients contained a higher proportion of kappa III+ cells reactive for the kappa IIIb-associated 17-109 idiotope (P less than 0.01) and larger G6 (P less than 0.02) and H1 (P less than 0.01) positive B cell populations than those within inflamed submandibular salivary glands. Furthermore, in labial glands there was a significant correlation between numbers of 17-109 and G6 idiotope reactive cells (r = 0.61; P less than 0.02), reflecting the known association between these H and L chain CRIs in RF IgM paraproteins. These results indicate that B cells bearing both VKIII and VHI-associated CRI are increased in the glandular infiltrates in Sjögren's syndrome and support the idea that this condition is associated with proliferation of immature B cell clones retaining germ-line V genes.

Primed and naive helper T cells in labial glands from patients with Sjogren's syndrome.

This study has investigated the presence and distribution of B cells, T cells and T-cell subsets within labial glands of patients with primary Sjogren's syndrome (n = 9) and secondary Sjogren's syndrome associated with rheumatoid arthritis (n = 8) using a sequential double immunoperoxidase technique and true colour image analysis. The composition of the inflammatory infiltrates was similar in glands from both patient groups. B cells were normally present within large foci with few detected in diffuse infiltrates such that the ratio of T:B cells in foci (2.4:1) was significantly lower than in diffuse infiltrates (7.3:1; P less than 0.001). In all infiltrates helper T cells (CD8-, CD3+) predominated over suppressor/cytotoxic cells (CD8+, CD3+; 2.7:1). Analysis of primed (CD45RA-, CD45RO+) and naive (CD45RA+, CD45RO-) CD8- T cells showed that the ratio of the primed to naive subset was significantly higher in focal (4.2:1) compared to diffuse (1.5:1; P less than 0.001) areas of lymphoid infiltration. These results indicate that the focal lymphocytic infiltrates characteristic of Sjogren's syndrome contain B cells associated with a T-cell population consisting predominantly of primed CD8- helper T cells. This latter population may be responsible for upregulating glandular B-cell activity in Sjogren's syndrome.