Interleukin-35 has a Protective Role in Infectious Mononucleosis-Induced Liver Inflammation Probably by Inhibiting CD8+ T Cell Function

Interleukin (IL)-35 plays an immunosuppressive role in infectious diseases, autoimmune disorders, and cancers. However, IL-35 expression and its regulation of CD8⁺ T cells in infectious mononucleosis (IM) are not fully understood. In this study, three groups of participants were compared, including twenty-three patients of IM without liver inflammation, twenty-eight patients of IM with liver inflammation, and twenty-one controls. Plasma and peripheral blood mononuclear cells (PBMCs) were isolated. CD8⁺ T cells were purified. Plasma IL-35 was measured by ELISA. PBMCs and CD8⁺ T cells were stimulated with recombinant human IL-35 in vitro. Perforin and granzyme B secretion was assessed by ELISPOT. Immune checkpoint molecule expression was investigated by flow cytometry. CD8⁺ T cells were co-cultured with HepG2 cells in direct contact and indirect contact manner. The cytotoxicity of CD8⁺ T cells was calculated by measuring lactate dehydrogenase release and proinflammatory cytokine expression. There was no significant difference in plasma IL-35 levels between patients with IM without liver inflammation and the controls, but the IL-35 level was notably increased in patients with IM who presented with liver inflammation and negatively correlated with aminotransferase. CD8⁺ T cells in patients with IM with liver inflammation showed stronger cytotoxicity. IL-35 stimulation inhibited CD8⁺ T cell-induced target cell death in patients with IM, mainly through suppression of IFN-γ/TNF-α secretion and elevation of immune checkpoint molecule expression, but did not affect perforin or granzyme B secretion. The current data indicated that IL-35 dampened the cytotoxicity of CD8⁺ T cells in patients with IM probably via repression of cytokine secretion. Elevated IL-35 may protect against CD8⁺ T cell-induced liver inflammation in patients with IM.

Dynamically Expressed miR-BART16 Functions as a Suppressor of CAND1 in Infectious Mononucleosis Caused by Epstein-Barr Virus in Children

OBJECTIVE

MiR-BART16 is a newly discovered Epstein-Barr Virus-encoded microRNA (miRNA). We aimed to explore the role of EBV-miR-BART16 in infectious mononucleosis (IM).

METHODS

Peripheral blood lymphocyte subsets were analyzed in 30 IM and 10 healthy children by flow cytometry. MiR-BART16 and its targets were measured by real-time PCR, western blot, ELISA, and dual-luciferase assay.

RESULTS

Serum miR-BART16 expression was significantly higher in the IM children than that in the healthy children, and was positively correlated with EBV copy number. Receiver operating characteristic analysis revealed serum miR-BART16 could differentiate IM and healthy individuals (P=0.0041). CAND1 was targeted and downregulated by miR-BART16 in an EBV infection-dependent way.

CONCLUSIONS

These results highlight that EBV-miR-BART16 plays an important role in regulating the expression of CAND1 to affect pediatric IM.

The Effects of Epstein-Barr Virus Nuclear Antigen 2 (EBNA2) on B-Lymphocytic Activity

BACKGROUND

Epstein-Barr virus is a worldwide disease that can cause a wide range of human diseases, the person will become a lifelong carrier of the virus once infected. To investigate the mechanism of Epstein-Barr virus nuclear antigen 2 (EBNA2) on B-lymphocytic activity, sera from 35 patients with infectious mononucleosis and from 34 cases without Epstein-Barr virus infection are collected for experimental analysis.

METHODS

Quantitative real-time PCR, western blot, and MTT assays were used to evaluate the relative expression level of EBNA2 and to examine its impact on cell vitality.

RESULTS

Research found that the average EBNA2 mRNA and protein levels in 35 patients with infectious mononucleosis were higher than that 34 cases without Epstein-Barr virus infection. The MTT assay indicates that EBNA2 can promote the growth and proliferation of B lymphocytes.

CONCLUSIONS

Combining the above implies that EBNA2 plays an important role in diseases that are induced by the Epstein-Barr virus. Other experiments reveal that ATO promotes the degradation of EBNA2 protein and induces the apoptosis of B lymphocytes which are EBNA2-positive.

Proteome-wide analysis of CD8+ T cell responses to EBV reveals differences between primary and persistent infection

Human herpesviruses are antigenically rich agents that induce strong CD8+T cell responses in primary infection yet persist for life, continually challenging T cell memory through recurrent lytic replication and potentially influencing the spectrum of antigen-specific responses. Here we describe the first lytic proteome-wide analysis of CD8+ T cell responses to a gamma1-herpesvirus, Epstein-Barr virus (EBV), and the first such proteome-wide analysis of primary versus memory CD8+ T cell responses to any human herpesvirus. Primary effector preparations were generated directly from activated CD8+ T cells in the blood of infectious mononucleosis (IM) patients by in vitro mitogenic expansion. For memory preparations, EBV-specific cells in the blood of long-term virus carriers were first re-stimulated in vitro by autologous dendritic cells loaded with a lysate of lytically-infected cells, then expanded as for IM cells. Preparations from 7 donors of each type were screened against each of 70 EBV lytic cycle proteins in combination with the donor's individual HLA class I alleles. Multiple reactivities against immediate early (IE), early (E) and late (L) lytic cycle proteins, including many hitherto unrecognised targets, were detected in both contexts. Interestingly however, the two donor cohorts showed a different balance between IE, E and L reactivities. Primary responses targeted IE and a small group of E proteins preferentially, seemingly in line with their better presentation on the infected cell surface before later-expressed viral evasins take full hold. By contrast, target choice equilibrates in virus carriage with responses to key IE and E antigens still present but with responses to a select subset of L proteins now often prominent. We infer that, for EBV at least, long-term virus carriage with its low level virus replication and lytic antigen release is associated with a re-shaping of the virus-specific response.

DR3 regulation of apoptosis of naive T-lymphocytes in children with acute infectious mononucleosis

Acute infectious mononucleosis (AIM) is a widespread viral disease that mostly affects children. Development of AIM is accompanied by a change in the ratio of immune cells. This is provided by means of different biological processes including the regulation of apoptosis of naive T-cells. One of the potential regulators of apoptosis of T-lymphocytes is a death receptor 3 (DR3). We have studied the role of DR3 in the regulation of apoptosis of naive CD4⁺ (nTh) and CD8⁺ (nCTL) T-cells in healthy children and children with AIM. In healthy children as well as in children with AIM, the activation of DR3 is accompanied by inhibition of apoptosis of nTh. In healthy children, the stimulation of DR3 resulted in the increase in apoptosis of nCTL. On the contrary, in children with AIM, the level of apoptosis of nCTL decreased after DR3 activation, which is a positive contribution to the antiviral immune response. In children with AIM, nCTL are characterized by reduced level of apoptosis as compared with healthy children. These results indicate that DR3 can be involved in the reduction of sensitivity of nCTL to apoptosis in children with AIM.

Detection of Epstein-Barr virus DNA in human tumors

The presence of Epstein-Barr virus (EBV) DNA in biopsies of human tumors was tested by complementary RNA (cRNA) hybridization on membranes and DNA-DNA reassociation kinetics. DNA-DNA reassociation kinetics can detect as few as 1 EBV genome in every 50 cells, and the cRNA method can detect EBV genomes if 2 or more are present in a cell. Twenty-three out of 24 African Burkitt's lymphoma biopsies, 18 out of 23 African nasopharyngeal carcinomas (NPC), and 8 out of 24 other African tumors were positive for EBV DNA. Three cases of American Burkitt's lymphoma were tested by the cRNA method, and EBV DNA was not detected. Three out of 25 American tumors other than American Burkitt's lymphoma contained 0.1 to 0.3 genomes per cell of EBV DNA.

Epstein-Barr virus effect on frequency of functionally distinct T cell subsets in children with infectious mononucleosis

PURPOSE

Epstein-Barr virus is a common human pathogen which infects the great majority of population worldwide. A striking proliferation of CD8⁺ T cells is an immune response to EBV invasion of B lymphocytes during infectious mononucleosis. The aim of the study was to analyze frequencies of CD28⁺CD95⁻, CD28⁺CD95⁺, CD28⁻CD95⁺ T cell subsets putative naïve (T(N)), central (T(CM)) and effector memory (T(EM)) T cells in children with infectious mononucleosis.

MATERIAL/METHODS

Multiparameter flow cytometric analysis of CD4⁺ and CD8⁺ T cell subsets was performed in 19 children with acute infectious mononucleosis.

RESULTS

The CD4⁺/CD8⁺ ratio was found to be decreased (0.53) in children with infectious mononucleosis. Median T(N), T(CM), T(EM) frequencies were estimated to be 3.7, 4.5, 15.1% of CD8⁺ and 23, 59.3, 5.5% of CD4⁺ T cells, respectively. In the present study we demonstrated negative correlations between CD8⁺CD28⁺CD95⁺ and CD8⁺CD28⁻CD95⁺ T cells and both VCA IgM antibody titers and disease duration. However, no such correlation was found when subset of CD4⁺ T cells or CD8⁺CD28⁺CD95⁻ cells was compared.

CONCLUSIONS

We conclude that there is a rapid decrease in the number of memory CD8⁺ T cells in early acute stage of infectious mononucleosis.

[Lipid peroxidation, antioxidative system and platelet component of homeostasis in patients with infectious mononucleosis]

The authors consider parameters of lipid peroxidation, antioxidative system and platelet component of homeostasis in patients with infectious mononucleosis.

[Measurement of B-lymphocyte stimulator mRNA expression in children with infectious mononucleosis by real-time fluorescence quantitative method]

OBJECTIVE

B cell multiplication plays a key role in infections mononucleosis. The present study was designed to detect the expression of B-lymphocyte stimulator (BLyS) mRNA in peripheral blood using real-time fluorescence quantitative polymerase chain reaction (RFQ-PCR) in children with infectious mononucleosis in order to explore the role of BLys in this disorder.

METHODS

Specific primers and TaqMan probes of BLyS were designed, and fluorescence of the PCR products were detected continuously during amplification. According to the standard curves created by plasmid DNA, the expression level of target genes in clinical samples were calculated using Stata Software version 8.0, and the results were presented as the ratio of copies of target gene mRNA to beta2 microglobulin (beta2M) mRNA copies. BLyS mRNA expression in peripheral blood was measured by RFQ-PCR in 18 children with infectious mononucleosis and the results were compared with those measured in 15 healthy controls.

RESULTS

The range of target gene mRNA detected by REQ-PCR was from 109 ng/L to 101 ng/L. The coefficient of variation for intra-experimental and inter-experimental reproducibility ranged from 1.88% to 5.89% and 6.32% to 12.34%, respectively. BLyS mRNA expression in peripheral blood in children with infectious mononucleosis were significantly higher than that in controls (1.65+/-0.10 vs 0.56+/-0.08; P < 0.01).

CONCLUSIONS

RFQ-PCR has a high sensitivity and reproducibility for the measurement of BLyS mRNA expression. BLyS may be involved in the development of infectious mononucleosis.

T-cell receptor triggering differentially regulates bim expression in human lymphocytes from healthy individuals and patients with infectious mononucleosis

Bim, a proapoptotic member of the Bcl-2 protein family, is a major regulator of central and peripheral T-cell deletion. Regulation of Bim activity by T-cell receptor (TCR) triggering is not well understood. We investigated expression of Bim in different subpopulations of ex vivo isolated human T cells from healthy donors and patients with infectious mononucleosis (IM). Upregulation of Bim expression in response to TCR-triggering was observed only in a small proportion of analyzed samples of peripheral blood lymphocytes (PBLs) from healthy donors and only occasionally upon longitudinal analysis of cells isolated from the same individuals. Populations of naive or memory T cells enriched on the basis of CD45RO or CD45RA expression showed only slight and comparable Bim upregulation. In contrast, ex vivo isolated PBLs from IM patients in the acute stage of the disease with significant expansions of CD8+ cells expressed increased levels of Bim, and lymphocytes from the majority of analyzed IM patients exhibited significant upregulation of all major Bim isoforms in response to TCR triggering. These results demonstrate that at least some antigen-induced expansions of human CD8+ T cells are associated with increased levels of Bim, and TCR triggering in effector T lymphocytes may increase Bim activity by upregulation of its expression.

Different T-bet expression patterns characterize particular reactive lymphoid tissue lesions

AIMS

To investigate T-bet expression profiles in various lymphoid tissue diseases caused by intracellular pathogens and to compare them in disorders without an infective aetiology. Murine and in vitro experiments have shown that the expression/induction of T-bet, the master regulator of Th1 differentiation, can be achieved by obligate intracellular pathogens and high interferon (IFN)-gamma levels.

METHODS

Lymph node biopsies were analysed immunohistochemically employing single and double labelling for T-bet and CD20, CD4, CD8 and CD30 detection.

RESULTS

In disorders associated with high IFN-gamma levels and intracellular pathogens (infectious mononucleosis, HIV-associated lymphadenopathy, cat-scratch disease, and toxoplasmic lymphadenitis), T-bet-expressing CD4 cells were accompanied by significant numbers of T-bet-positive CD8 and B cells. A similar profile was also found in histiocytic necrotizing (Kikuchi) lymphadenitis, a disease of unknown cause. In contrast, T-bet expression in disorders without an infective aetiology was observed in only a small portion of lymphocytes.

CONCLUSIONS

Increased T-bet expression does not only identify intracellular infections in lymphoid tissue associated with high IFN-gamma levels, but also implies that, under these conditions, it becomes induced in B cells, which apparently support the Th1 response. T-bet expression in Kikuchi lymphadenitis underscores the hypothesis that it is caused by an intracellular microorganism.

Preliminary evidence of mitochondrial dysfunction associated with post-infective fatigue after acute infection with Epstein Barr virus

BACKGROUND

Acute infectious diseases are typically accompanied by non-specific symptoms including fever, malaise, irritability and somnolence that usually resolve on recovery. However, in some individuals these symptoms persist in what is commonly termed post-infective fatigue. The objective of this pilot study was to determine the gene expression correlates of post-infective fatigue following acute Epstein Barr virus (EBV) infection.

METHODS

We followed 5 people with acute mononucleosis who developed post-infective fatigue of more than 6 months duration and 5 HLA-matched control subjects who recovered within 3 months. Subjects had peripheral blood mononuclear cell (PBMC) samples collected at varying time points including at diagnosis, then every 2 weeks for 3 months, then every 3 months for a year. Total RNA was extracted from the PBMC samples and hybridized to microarrays spotted with 3,800 oligonucleotides.

RESULTS

Those who developed post-infective fatigue had gene expression profiles indicative of an altered host response during acute mononucleosis compared to those who recovered uneventfully. Several genes including ISG20 (interferon stimulated gene), DNAJB2 (DnaJ [Hsp40] homolog and CD99), CDK8 (cyclin-dependent kinase 8), E2F2 (E2F transcription factor 2), CDK8 (cyclin-dependent kinase 8), and ACTN2 (actinin, alpha 2), known to be regulated during EBV infection, were differentially expressed in post-infective fatigue cases. Several of the differentially expressed genes affect mitochondrial functions including fatty acid metabolism and the cell cycle.

CONCLUSION

These preliminary data provide insights into alterations in gene transcripts associated with the varied clinical outcomes from acute infectious mononucleosis.

[Trend of the CD23+ B cells in children with infectious mononucleosis caused by Epstein-Barr virus]

OBJECTIVE

Epstein-Barr virus (EBV) is a common causative agent of infectious mononucleosis (IM) and capable of efficiently immortalizing primary B cells into continuously growing lymphoblastoid cells in vitro. As B cell activation antigen, CD23 expression is induced by EBV infection of B cells and remains constitutively expressed at high levels in virtually all EBV-immortalized cells, which have been strongly linked to the development of B-cell lymphoproliferative disease and lymphoma. Whereas previous studies were performed in vivo in animals or ex vivo cultures, the present study aimed to explore the role of EBV-immortalized cells (CD23(+)/CD19(+)) in vivo analysis of children with EBV-IM.

METHODS

In a prospective trial, a group of 30 patients with IM (18 boys and 12 girls) with mean age of 3.9 +/- 1.3 years (range 6 months to 8 years) were enrolled. Clinical diagnosis of IM was confirmed based on fever, lymphadenopathy, splenomegaly, lymphocytosis (> 50%), atypical lymphocytes (> 10%) in blood smears and the elevated levels of IgM antibody against EBV capsid antigen. The day of onset of fever was recognized as day 1 of illness. Blood samples taken during acute (3 - 5 days), early convalescent (about 11 - 15 days) and convalescent phase (about 30 - 45 days) were analyzed for expressions of CD19(+)/CD23(+), CD23, CD19 on peripheral blood mononuclear cells by flow cytometry (FCM) and was compared with those of control group.

RESULTS

(1) The levels of CD23(+)/CD19(+) and CD23 expressions were markedly decreased in acute stage [CD23(+)/CD19(+) (2.22 +/- 1.47)%, (132 +/- 91)/mm(3); CD23 (3.12 +/- 1.88)%, (195 +/- 102)/mm(3)] and in early convalescent stage [CD23(+)/CD19(+) (4.51 +/- 2.25)%, (166 +/- 85)/mm(3); CD23 (5.55 +/- 2.76)%, (231 +/- 130)/mm(3)] in patients with IM as compared with those of the healthy controls [CD23(+)/CD19(+) (6.71 +/- 2.25)%, (215 +/- 68)/mm(3); CD23 (7.85 +/- 3.09)%, (249 +/- 86)/mm(3), respectively]. The earlier the history was, the lower the expressive levels were. The levels of CD23(+)/CD19(+) expressions returned to, but those of CD23 expressions exceeded, normal level in convalescent stage [CD23(+)/CD19(+) (6.72 +/- 2.16)%, (213 +/- 108)/mm(3); CD23 (9.46 +/- 2.73)%, (366 +/- 200)/mm(3)]. (2) There was a positive correlation in the expressions of CD23(+)/CD19(+) and CD23 among the three stages (P < 0.01). The positive correlation between the expressions of CD23(+)/CD19(+) and CD19 only occurred during acute stage (P < 0.01). There was no correlation between the expressions of CD23 and CD19 (P > 0.05).

CONCLUSION

EBV-immortalized cells and CD23(+) cells were inhibited effectively during the acute and early convalescent stage of IM. With the recovery of the disease, they gradually recovered and the levels of CD23 expressions exceeded normal level in convalescent stage.

Fatal infectious mononucleosis with evidence suggestive of the development of B cell lymphoma

A 4-year-old girl presented to a local hospital in August 1999 with fever and cervical lymphadenopathy. A diagnosis of Epstein-Barr virus (EBV) infection was made and the patient was treated with corticosteroids. One month later she developed dyspnea secondary to tonsilar swelling, and underwent tonsillectomy and adenoidectomy. Her dyspnea increased, however, and by mid September she required mechanical ventilation. Six weeks later, she was transferred to Chiba Children's Hospital (Chiba, Japan). Despite vigorous treatment, she died within four weeks of admission. At autopsy, microscopic examination revealed numerous histiocytes with frequent hemophagocytosis in her lungs, liver, spleen, thymus, and lymph nodes. The tentative diagnosis was EBV-associated hemophagocytic syndrome (EBVAHS). A proliferation of atypical lymphocytes was observed in the lymph nodes, the majority of which stained positive with CD79a antibody. A whitish nodule, 8 mm in diameter, was noted in her right ovary. It consisted of a proliferation of pleomorphic lymphoid cells expressing CD79a antigen. In situ hybridization detected EBV RNA within CD79a antigen-positive cells in the lungs, spleen, thymus, bone marrow, lymph nodes, and the right ovary. Polymerase chain reaction analysis of DNA from the ovarian nodule demonstrated a monoclonal rearrangement of the immunoglobulin heavy chain gene indicating that it consisted of a clone of B lymphocytes. We suggest that EBVAHS develops into polyclonal and monoclonal lymphoproliferative disorder in a short period, and that EBVAHS is a preneoplastic condition that may result in B cell lymphoma.

Lymph node lesion in infectious mononucleosis showing geographic necrosis containing cytologically atypically B-cells. A case report

Lymph node lesions in infectious mononucleosis (IM) show a marked histological diversity and may occasionally be confused with malignant lymphoma. We report on a rare case of IM showing geographic lymph node necrosis as well as angiocentric lymphoproliferative lesions, and containing numerous centroblasts, immunoblasts and Reed-Sternberg (RS)-like cells. The patient was a 40-year-old Japanese man with signs and symptoms of classical IM. This was later confirmed serologically, but the necrotic area comprised 50% of a cervical lymph node. The large lymphoid cells, including RS-like cells, were CD3-, CD5-, CD15-, CD20+, CD30+, CD45RO-, CD79a+, LMPI+, and EBNA2+. In situ hybridization study also disclosed that these cells were associated with Epstein-Barr virus (EBV). The patient was disease free during a follow-up of 15 years. Although the classical IM syndrome rarely shows a close resemblance to lymphomatoid granulomatosis of the lymph node or to EBV+ B- cell lymphoproliferative disorders associated with an immunodeficient state on histology, it is important for pathologists to be aware of this type of lesion in diagnostic practice.

Down-regulation of pan-T-cell antigens, particularly CD7, in acute infectious mononucleosis

Multiparameter flow cytometric analysis was performed on the peripheral blood samples from 25 patients with acute infectious mononucleosis. Phenotypic results were matched with those for patients without viral symptomatology. Samples from all patients with infectious mononucleosis exhibited an activated (HLA-DR+, CD38+) CD8+ cytotoxic-suppressor T-cell population with aberrant down-regulation of CD7, and samples from 2 (8%) of 25 patients also showed down-regulation of CD5. The CD8+ cells also were slightly larger than normal T cells by forward scatter characteristics. None of the control samples showed down-regulation of either antigen. Aberrant pan-T-cell antigenic expression is a criterion in the immunophenotypic diagnosis of T-cell lymphoproliferative disorders. Acute Epstein-Barr virus infection should be considered in the differential diagnosis when down-regulation of CD7 is present, especially in conjunction with an activated CD8+ T-cell population.

Paul-Bunnell antigen and a possible mechanism of formation of heterophile antibodies in patients with infectious mononucleosis

Sera of patients with infectious mononucleosis contain heterophile anti-Paul- Bunnell (PB) antibodies to erythrocytes of numerous mammalian species. Evidence is presented that the corresponding antigen of bovine erythrocytes is not, as previously described, a single molecule, but a series of glycoproteins with glycans terminated with N-glycolylneuraminic acid (Neu5Gc). The latter compound should be an important part of the PB epitope because, in agreement with the results of others, we found that desialylation of the PB antigen abolishes almost completely its activity. We examined three different preparations of GM3 ganglioside for their capacity to bind anti-PB and found that only GM3 from horse erythrocytes containing Neu5Gc exhibited a low although ELISA measurable PB activity. The other two GM3 preparations, from bovine milk and dog erythrocytes, containing N-acetylneuraminic acid (Neu5Ac) bound little if any anti-PB antibodies. This finding confirms a previous report that human erythrocyte Neu5Ac containing sialoglycoprotein with similar O-linked glycans as the PB-antigen of bovine erythrocytes exhibits only very low PB activity (Patarca & Fletcher, 1995, Crit Rev Oncogen., 6: 305). In conclusion, we present a hypothesis that anti-PB antibodies in patients with infectious mononucleosis are formed against infection-induced cell membrane glycoconjugates containing highly immunogenic Neu5Gc.

Lymph node infarction associated with infectious mononucleosis: report of a case resembling lymph node infarction associated with malignant lymphoma

A completely infarcted lymph node should alert the pathologist to the high possibility of malignant lymphoma. The lymph node lesion of infectious mononucleosis (IM) shows marked histologic diversity and occasionally may be confused with malignant lymphoma. We report a rare case of IM showing extensive lymph node infarction whose lymph node lesion was similar to lymph node infarction associated with malignant lymphoma. This case describes a 32-year-old Japanese man who had signs and symptoms consistent with IM, which he was later proven serologically to have, but whose cervical lymph node showed extensive lymph node infarction with a thin area of granulation tissue beneath the capsule. The infarcted tissue contained numerous eosinophilic ghosts of large lymphoid cells. The thin granulation tissue was composed of numerous small lymphocytes, plasma cells, and histiocytes, in addition to large lymphoid cells including immunoblasts and granulocytes. CD20, CD3, and CD45RO immunostains revealed the mixed B- and T-cell nature of the ghosts of large lymphoid cells in the infarcted tissue as well as viable large cells in the granulation tissue. The patient was free from disease after 50 months' follow-up.

[Nucleic acid content in peripheral blood lymphocytes from patients with infectious mononucleosis]

An increase in RNA content in peripheral blood lymphocytes and increased number of macronuclear weakly basophilic cells (presumably due to increased content of B-lymphocytes which, in contrast to sharply basophilic T-lymphocytes, are characterized by light basophilic cytoplasm) are observed in patients with infectious mononucleosis. Macronuclear forms represented equally by hyper- and hypobasophilic elements predominate the structure of atypical mononuclears. Increased content of DNA in the peripheral blood lymphocytes is due to increased number of cells with high DNA content in the patient's blood and appearance of cells with 52-65 arb. units DNA (blast-transformed atypical mononuclears infected with the virus) which are normally absent.

Accumulation of p53 in infectious mononucleosis tissues

Epstein-Barr virus (EBV) infects lymphocytes, where it persists indefinitely for the life of the host; whether the virus interacts with p53 to maintain itself in these cells is unknown. Lymphoid biopsy samples from 10 patients with infectious mononucleosis (IM) were examined for expression of p53 by immunohistochemistry. Accumulation of p53 was detected in all 10 cases, primarily in large lymphocytes of the expanded paracortex. The presence of EBV was confirmed in all 10 cases by EBER1 (EBV-encoded RNA) in situ hybridization, whereas 11 non-IM control samples lacked significant EBER1 and did not express p53 in paracortical lymphocytes. Interestingly, EBV infection alone does not cause accumulation of intracellular p53, because many more cells expressed EBER1 than p53 in the IM tissues. To determine whether p53 was confined to the subset of infected cells in which viral replication was occurring, BZLF1 immunostains were performed. Viral BZLF1 was detected in 8 of 10 IM tissues; however, the paucity and small size of the BZLF1-expressing lymphocytes suggests that they are not the same cells overexpressing p53. To further examine the relationship between p53 and EBV gene expression, the tissues were studied for latent membrane protein 1 (LMP1) expression by immunohistochemistry. Viral LMP1 was observed in the large paracortical lymphocytes of all 10 cases of IM, indicating co-localization of p53 and LMP1 in these cells. Our findings confirm that p53 overexpression is not specific for nodal malignancy and that p53 accumulation is characteristic of IM. Because p53 was not coexpressed in the same cells as BZLF1, it appears that BZLF1 is not directly responsible for p53 accumulation. Nevertheless, co-localization of p53 and LMP1 in activated-appearing lymphocytes suggests that EBV infection is responsible for p53 accumulation. HUM PATHOL 31:1397-1403.

Epstein-Barr virus induces Fas (CD95) in T cells and Fas ligand in B cells leading to T-cell apoptosis

Epstein-Barr virus (EBV) acute infectious mononucleosis (AIM) is characterized by transient immunosuppression in vivo and increased T-cell apoptosis after ex vivo culture of AIM peripheral blood mononuclear cells. We undertook experiments to test whether EBV or purified virion envelope glycoprotein gp350 could contribute to Fas-mediated T-cell apoptosis. Our in vitro results indicate that EBV increased Fas expression in CD4(+) T cells and Fas ligand (FasL) expression in B cells and macrophages. Purified gp350 was also shown to significantly increase CD95 expression in CD4(+) T cells. When T-cell CD95 was cross-linked, EBV-stimulated T cells underwent apoptosis. The induction of T-cell CD95 by EBV followed by CD95 cross-linking with anti-CD95 monoclonal antibody resulted in a loss in the number of T cells responding to the T-cell mitogens, anti-CD3 antibody, and interleukin-2. These results indicate that, in addition to serving as a principal ligand for the attachment of virus to target cells, gp350 may also act as an immunomodulatory molecule that promotes T-cell apoptosis.

Antiapoptotic marker Bcl-X(L), expression on Reed-Sternberg cells of Hodgkin's disease using a novel monoclonal marker, YTH-2H12

Inhibitors of apoptosis may regulate tissue differentiation and promote cell survival in neoplasia. A new apoptosis inhibitor of the bcl-2 gene family, bcl-X(L), was recently found in some types human neoplasia but not in normal tissue. We investigated bcl-X(L) expression in 419 cases of normal and neoplastic lymphoid lesions using immunohistochemistry with the monoclonal antibody bcl-X(L) (YTH-2H12). Ninety-four percent (141/150) of classic Hodgkin's disease (HD) were positive for bcl-X(L) with strong intensity in most Reed-Sternberg (RS) cells. Forty-eight percent (38/80) of nodular lymphocyte predominance (LPHD) were positive. In the non-Hodgkin's lymphomas (NHL), bcl-X(L) was expressed in a low percentage of cases (< 20%), with the exception of follicle center lymphoma, grade III/III (78%). All reactive hyperplastic lesions were negative for bcl-X(L). RS cells, which expressed bcl-X(L), were not labeled by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). We found RS cells expressing bcl-X(L) were absent of DNA fragmentation (apoptosis). Our data provide evidence that bcl-X(L) is abnormally expressed in the RS cells of HD and some types of NHL raising speculation that inhibition of apoptosis may be important in the pathogenesis of lymphoma, specifically HD. In addition, the previously reported correlation between bcl-X(L) and Epstein-Barr virus expression in HD was not supported by this study.

Interleukin-18, interferon-gamma, IP-10, and Mig expression in Epstein-Barr virus-induced infectious mononucleosis and posttransplant lymphoproliferative disease

T cell immunodeficiency plays an important role in the pathogenesis of posttransplant lymphoproliferative disease (PTLD) by permitting the unbridled expansion of Epstein-Barr virus (EBV)-infected B lymphocytes. However, factors other than T cell function may contribute to PTLD pathogenesis because PTLD infrequently develops even in the context of severe T cell immunodeficiency, and athymic mice that are T-cell-immunodeficient can reject EBV-immortalized cells. Here we report that PTLD tissues express significantly lower levels of IL-18, interferon-gamma (IFN-gamma), Mig, and RANTES compared to lymphoid tissues diagnosed with acute EBV-induced infectious mononucleosis, as assessed by semiquantitative RT-PCR analysis. Other cytokines and chemokines are expressed at similar levels. Immunohistochemistry confirmed that PTLD tissues contain less IL-18 and Mig protein than tissues with infectious mononucleosis. IL-18, primarily a monocyte product, promotes the secretion of IFN-gamma, which stimulates Mig and RANTES expression. Both IL-18 and Mig display antitumor activity in mice involving inhibition of angiogenesis. These results document greater expression of IL-18, IFN-gamma, Mig, and RANTES in lymphoid tissues with acute EBV-induced infectious mononucleosis compared to tissues with PTLD and raise the possibility that these mediators participate in critical host responses to EBV infection.

Tumor necrosis factor receptor-associated factor 1 is overexpressed in Reed-Sternberg cells of Hodgkin's disease and Epstein-Barr virus-transformed lymphoid cells

The tumor necrosis factor (TNF) receptor-associated factor 1 (TRAF1) is a member of the recently defined TRAF family. It takes part in the signal transduction of the TNF receptor 2 (TNFR2), the lymphotoxin-beta receptor (LT-betaR), CD40, CD30, and LMP1; is induced by LMP1 in vitro; and protects lymphoid cells from apoptosis. To identify the cells in which TRAF1 is active in vivo, we studied TRAF1 transcripts in normal lymphoid tissue, in Epstein-Barr virus (EBV)-induced lymphoproliferations, and in malignant lymphomas with special reference to those that overexpress the cytokine receptor CD30 and CD40 of the TNF receptor family at the single-cell level using a radioactive in situ hybridization. In normal lymphoid tissue, TRAF1 message proved to be absent from all resting B and T cells as well as from macrophages and accessory cells (follicular dendritic cells and interdigitating cells) and present in few perifollicular and intrafollicular lymphoid blasts. In contrast, there was a high and consistent TRAF1 overexpression in EBV-induced lymphoproliferations and Hodgkin's disease. Nearly all non-Hodgkin's lymphoma show low or no TRAF1 expression. Only some cases of diffuse large B-cell lymphoma showed a moderate to high TRAF1 signal. Several of the latter cases were EBV+. These data confirm that TRAF1 is an inducible molecule and indicates its deregulation in the mentioned disorders with the potential of a blockage of the apoptotic pathway.

Redox control of Epstein-Barr virus replication by human thioredoxin/ATL-derived factor: differential regulation of lytic and latent infection

Human thioredoxin (hTRX)/adult T-cell leukemia (ATL)-derived factor (ADF) was originally reported as an interleukin-2 (IL-2) receptor-alpha-inducing factor produced by human T-cell lymphotropic virus-1-positive (HTLV-1+) cell lines. Growing evidence indicates that hTRX/ADF plays important roles in cellular responses against oxidative stress and is involved in a variety of cellular functions. A high level of hTRX/ADF expression is also observed in other human virus-infected cell lines including those of Epstein-Barr virus (EBV) and human papillomavirus. In this report, we analyzed the effect of hTRX/ADF on lytic amplification and persistent replication of EBV as a model for lytic versus latent phase of viral replication in host cells. Addition of hTRX/ADF clearly suppressed lytic replication of EBV in Raji cells and B95-8 cells induced to the lytic phase of 12-O-tetradecanoylphorbol-13-acetate (TPA), and it prevented the death of these cells evoked by the lytic induction. In contrast, hTRX/ADF did not have any effect on persistent replication in the latent phase. These data indicated that hTRX/ADF prevents EBV-transformed cells from proceeding into the lytic phase and regulates cohabitation of EBV and its host cells.

CD95 (Fas) ligand expression of Epstein-Barr virus (EBV)-infected lymphocytes: a possible mechanism of immune evasion in chronic active EBV infection

The Epstein-Barr virus (EBV) induces infectious mononucleosis (IM) and can be associated with chronic active EBV infection (CAEBV). Cytotoxic T lymphocytes (CTL) play an important role in excluding EBV-infected cells. Two cytotoxic mechanisms of CTL have been demonstrated: one perforin/granzyme-based and the other Fas (CD95)/Fas ligand (FasL)-based. To clarify these two pathways in CAEBV, we analyzed six patients with CAEBV and four patients with IM using immunohistochemical staining of the lymph nodes. In both CAEBV and IM, CD8+ T-cells increased in number, but CD56+ natural killer cells were rare. In four of six cases with CAEBV, approximately half the lymphocytes were positive for T cell-restricted intracellular antigens (TIA-1), which were recognized by the cytolytic granules of CTL. In IM, the number of TIA-1 positive cells was smaller than that in CAEBV. Fas-positive lymphocytes were frequently encountered in both CAEBV and IM. However, FasL-positive lymphocytes increased in three of six patients with CAEBV, but not in patients with IM. Except for one case with CAEBV, the number of perforin- and/or granzyme-positive cells was small in number in both CAEBV and IM cases. In double-staining FasL and EBV in situ hybridization, FasL-positive EBV-infected lymphocytes were detected in CAEBV but not in IM. In CAEBV, the Fas/FasL pathway and not perforin pathways appears to play an important role in the pathogenesis. The data suggest that EBV-infected lymphocytes may evade immune attack through the expression of FasL.

Epstein-Barr virus-infected B cells of males with the X-linked lymphoproliferative syndrome stimulate and are susceptible to T-cell-mediated lysis

Primary infection with the Epstein-Barr virus (EBV) results in fatal infectious mononucleosis in up to 70% of males affected by the X-linked lymphoproliferative syndrome (XLP). This rare disease is often associated with diverse natural killer (NK)-, B- and T-cell deficiencies. We describe experiments testing whether the B lymphocytes of affected males play a role in the pathogenesis of XLP due to a low susceptibility to T-cell-mediated immunity. Using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry we detected in these B cells the expression of viral proteins EBNA-1, EBNA-2, EBNA-3A, EBNA-3C, LMP-1 and LMP-2A, which provide targets for cytotoxic T cells. Major histocompatibility complex (MHC) class I, MHC class II and the B7 costimulatory molecule were present on the cell surface. Accordingly, the EBV-infected B cells were lysed in 51Cr-release assays by T lymphocytes sharing MHC determinants with the targets. This MHC-restricted and specific lysis was confirmed in competition experiments using MHC-specific monoclonal antibodies (MAbs) and synthetic peptides. XLP-derived LCLs could also induce MHC class I-restricted memory and cytotoxic T lymphocytes. Thus, these XLP-derived B cells resembled normal LCIs in vitro with respect to induction of EBV-specific cytotoxic T cells (CTL), the ability to present EB viral antigens and the susceptibility to EBV-specific and MHC-restricted CTL-mediated killing. The failure of the immune system to eliminate these virus-infected B cells in XLP is clearly not caused by a B-cell-specific defect.

Expression of vascular endothelial growth factor in lymphomas and Castleman's disease

Vascular endothelial growth factor (VEGF) is one of the main angiogenic cytokines in human solid tumours and inhibition of VEGF-induced angiogenesis suppresses tumour growth. Some groups of malignant lymphoma, including peripheral T-cell lymphomas and Hodgkin's disease, are characterized by a conspicuous proliferation of small vessels. To test the hypothesis that VEGF may also be involved in the angiogenesis in lymphomas and other lesions of the lymphoid system, VEGF expression was analysed in tissues, employing in situ hybridization with a 35S-labelled RNA probe specific for this cytokine. Significant expression of VEGF transcripts was observed in Hodgkin's disease and peripheral T-cell lymphomas, particularly of the angioimmunoblastic type. In contrast, expression of this cytokine was minimal or absent in follicle centre lymphoma and chronic lymphocytic leukemia of B-cell type. VEGF was mainly observed in reactive non-lymphoid CD68-negative cells, which probably represent fibroblasts or myofibroblasts. In normal and ulcerated tonsils, VEGF was expressed in the squamous epithelium but only rarely found in the lymphoid tissue. Although infectious mononucleosis tonsils contained high numbers of VEGF-positive cells in the interfollicular zone, expression of this cytokine was not found in Epstein-Barr virus (EBV)-infected cells, as determined by simultaneous in situ hybridization for VEGF and EBV-encoded small nuclear RNAs (EBER). In 5/8 cases of Castleman's disease, germinal centres containing small vessels also showed expression of VEGF, in contrast to normal tonsillar germinal centres which are devoid of both vessels and VEGF transcripts. It is concluded that VEGF may be involved in the induction of the angiogenesis of both peripheral T-cell lymphomas and Hodgkin's disease, but not in low-grade B-cell lymphomas. In contradistinction to solid tumours, in which this cytokine is commonly secreted by the tumour cells themselves, in malignant lymphoma VEGF is not a product of neoplastic cells. Vascularization of germinal centres in Castleman's disease may also be a consequence of abnormal local expression of VEGF.

Decreased expression of 20-kD homologous restriction factor (HRF20, CD59) on T lymphocytes in Epstein-Barr virus (EBV)-induced infectious mononucleosis

HRF20 (CD59) is one of the membrane-associated complement regulatory proteins. The characteristic function of CD59 is to prevent membrane attack complex (MAC) formation on the cell surface and to protect the cell from complement-mediated cell lysis. We examined the expression of CD59 antigen on T cell subpopulations in patients with acute infectious mononucleosis (IM) and analysed the relationship between the amount of CD59 expression and activation-induced cell death of mature T cells with apoptosis. Decreased expression of CD59 on CD8+ T cells, especially on CD45RO+ and HLA-DR+ activated T cells, was marked in acute IM patients. In contrast, activated CD4+ T cells from IM patients expressed as much CD59 antigen as CD4+ T cells from healthy volunteers. After incubation-induced cell death, viable CD8+ T cells showed normal amounts of CD59 antigen on their surface. CD59dim CD8+ T cells were more susceptible to apoptosis than CD59bright CD8+ T cells. These findings suggest that decreased expression of CD59 on CD8+ T cells may discriminate the susceptibility of activated CD8+ T cells to activation-induced cell death in IM.

Frequent expression of interleukin-10 by Epstein-Barr virus-harboring tumor cells of Hodgkin's disease

Tumor cells of Epstein-Barr virus (EBV)-associated Hodgkin's disease (HD) express the viral protein, latent infection membrane protein-1 (LMP1), but evade cytotoxic responses normally directed at this antigen. We tested whether local production of the immunoregulatory interleukins (IL)-4 and -10 may have a role in this process. IL-4 RNA was not detectable in any of the HD cases. By contrast, isotopic in situ hybridization and correlation with the presence of EBV gene products showed significantly higher proportions of cases with IL-10 expressing tumor cells in LMP1-positive (17 of 26, 66%) as compared with LMP1-negative HD cases (six of 37, 16%). Absence of EBV BCRF1 RNA indicated that the transcripts originated from the cellular IL-10 gene. Similarly, an association between IL-10 expression and EBV-infection of tumor cells was found in AIDS-related malignant non-Hodgkin lymphomas (ARL). Very small proportions of EBV-infected cells, mainly blasts, expressed IL-10 in infectious mononucleosis tonsils. Thus, although not entirely exclusive to EBV-positive cases, IL-10 expression is frequently associated with EBV-infection in HD and ARL and appears to be upregulated by EBV, most likely through LMP1. In view of the established inhibitory effects of IL-10 on cell mediated immunity, it is suggested that IL-10 expression may contribute to evasion of LMP1-positive cells from cytotoxicity directed at viral antigens.

Immunoblot analysis of cellular expression of Bcl-2 family proteins, Bcl-2, Bax, Bcl-X and Mcl-1, in human peripheral blood and lymphoid tissues

The ability of Bcl-2 to inhibit apoptotic cell death is well established. Several homologues of the bcl-2 gene, such as bax, bcl-x or mcl-1, have recently been identified. Like Bcl-2, both Bcl-XL and Mcl-1 appear to function as repressors of apoptotic cell death, whereas Bax facilitates it, indicating possible interactions among them in the control of cellular survival. To investigate the in vivo role of expression of bcl-2 gene family products, immunoblot analysis using corresponding specific antisera was performed for peripheral blood cells and some lymphoid tissues in humans. We demonstrated that all Bcl-2 family proteins were expressed at various levels in hematolymphoid cell subpopulations isolated from peripheral blood, tonsil, spleen and thymus. Lymphoid expression of Bcl-2 family proteins tended to increase following activation, but declined with time in culture. Loss of Bcl-2 in cultured lymphoid cells was especially marked. Sole expression of Bax, but not other members of the Bcl-2 family, was observed on neutrophils, seemingly reflecting their shortest life-span among blood leukocytes. The results support the notion that a balance of expression of Bcl-2 family proteins may regulate the life and death of hematolymphoid cells at different stages of cell differentiation and activation.

Patterns of cytokine gene expression in infectious mononucleosis

Primary infection with Epstein-Barr virus (EBV) may arise as infectious mononucleosis (IM) in adolescents and young adults. Morphologically, IM-affected lymphoid tissue is characterized by expanded interfollicular areas with formation of atypical lymphoid blasts. It is assumed that morphology and clinical presentation of IM are related to characteristic patterns of cytokine production by EBV-infected and reactive cells. We studied IM tonsils of eight patients and six normal tonsils with a double in situ hybridization procedure using [35S]-labeled RNA probes specific for various cytokines and digoxigenin-labeled probes for the detection of the nuclear EBV encoded RNA transcripts, EBER 1 and 2. All of the IM cases displayed the same distinct cytokine gene expression pattern. When compared with interfollicular areas of normal tonsils, expression of lymphotoxin (LT), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-1 beta, but not IL-8 or IL-1 alpha was strongly enhanced in interfollicular areas in IM tonsils. LT was expressed predominantly by EBV-infected cells. TNF-alpha transcripts were also present in EBV-infected cells, although in smaller proportions. IL-6 specific signals were only found in few EBV-infected cells. IL-1 alpha-, IL-1 beta-, and IL-8-specific signals were not observed in EBV-infected cells, but were present at high signal intensity in many cells within and around foci of EBV-infected cells (IL-1 beta), next to areas of necrosis (IL-8, IL-1 beta), or in epithelial cells (IL-1 alpha). These data suggest that EBV infection in form of IM results in induction of specific sets of cytokine genes in EBV-infected and in neighboring EBV-negative cells contributing to the characteristic morphology and cellular arrangement of the lesion as well as the clinical presentation.

Quantitative analysis of lymphocyte CD11a using standardized flow cytometry

CD11a is the alpha-subunit of the leucocyte adhesion and costimulation molecule LFA-1. We have refined the measurement of lymphocyte CD11a density with a FACScan using commercially available fluorescent beads for standardization and fluorescein-conjugated antibody to CD11a of known fluorescein: protein ratio. The fluorescence intensity of CD11a on peripheral blood CD4+ and CD8+ lymphocytes was measured in 60 healthy subjects. We demonstrated linear correlation between age and mean CD11a density (r = 0.47 for CD4+ cells, r = 0.71 for CD8+ cells). We established that there is a consistent logical cut off point at 4.3 x 10(3) bound antibody molecules between low-expressing and high-expressing subsets of CD8+ cells and we then investigated whether the variation in lymphocyte CD11a expression in healthy subjects was sufficiently small for the application of this method to the detection of abnormal groups or individuals. Analysis of the CD11a high subsets has high statistical power (> 99% in 60 subjects to detect a 25% difference) and good precision (< 4% differences). The advantages of the method for comparative studies of cell surface accessory molecules are discussed. We have also evaluated a frozen cell line for quality control, and demonstrated up-regulation of CD11a density on CD4+ and CD8+ cells measured in three patients with infectious mononucleosis.

Selective expression of the p70 subunit of the interleukin-2 receptor on lymphocytes from patients with infectious mononucleosis

The lymphocytosis manifested in infectious mononucleosis (IM) during acute phase is ascribed to a reactive expansion of CD8+ T lymphocytes caused by Epstein-Barr virus (EBV)-infected B lymphocytes. Expression of HLA-DR antigen on IM lymphocytes suggests that these T lymphocytes are somehow activated in vivo. In the present study, we analyzed the interleukin-2 (IL-2) receptor expression on lymphocytes from six patients with acute IM. Radiolabeled IL-2 binding assay revealed that IM lymphocytes from all patients examined had a considerable number of IL-2 binding sites with an intermediate affinity, although they did not express the IL-2 receptor recognized by anti-Tac antibody (p55). The number of binding sites (1,070 to 4,600 sites per cell) was larger than that of a normal, resting T lymphocyte-enriched population (650 sites per cell). Furthermore, IM lymphocytes showed marked proliferative responses to higher concentrations of IL-2, which were almost completely blocked by an anti-p70 IL-2 receptor antibody, indicating that their IL-2 receptor is a functional receptor. The results of an affinity cross-linking study seem to indicate that the IL-2 receptor expressed on IM lymphocytes is p70, the second chain of the IL-2 receptor distinct from p55. Flow cytometric analysis following immunofluorescent staining with anti-p70 IL-2 receptor antibody confirmed p70 expression on CD8+ HLA-DR+ lymphocytes. These data suggest that p70 IL-2 receptor expression is involved in the immune response triggered by EBV infection.

The metabolism of C3 and C4 in patients with immune complexes and normal complement levels

The metabolism of the complement proteins, C3 and C4 was examined in two groups of patients with a high incidence of detectable immune complexes but normal levels of complement components. The specific aim was to ascertain whether significant ongoing complement activation occurred in these patients. Eleven patients with rheumatoid arthritis (RA), 11 with infection and 11 control subjects were studied. Each received approximately 10 microCi 125l.C4 and 2.5 microCi 131l.C3 by intravenous injection. Analysis of turnover data showed that there was significant hypercatabolism of both C3 and C4 in the two study groups compared to controls. Plasma production of C4 was normal for both groups (despite the presence of C4 null alleles in six out of 11 of the RA group), while C3 production was significantly elevated in both RA and infection (p less than 0.01 and p less than 0.001 respectively). Patients with infection showed a significant increase in extravascular/intravascular distribution of both proteins. The data show that immune complex formation is associated with accelerated turnover of complement proteins, irrespective of co-existing tissue damage or changes in the serum concentration of complement components. The findings suggest that both activation of complement and maintenance or enhancement of protein synthesis are important for the efficient processing of immune complexes in vivo.

Epstein-Barr virus-infected B lymphoblastoid cell lines: dynamics of interferon and 2'5'-oligoadenylate synthetase activity

Levels of 2'-5'-oligoadenylate synthetase (2'-5'OAS) activity measured in cell-free extracts of 23 Epstein-Barr virus transformed beta lymphoblastoid cell lines (LCL) were measured. Enzyme activity was low during stationary or log phase growth, and rapidly rose to peak values during log phase. Peak levels of 2'-5'OAS activity were characteristic for each LCL, and were significantly higher (P less than 0.05) in lines derived from patients with infectious mononucleosis (IM) than in lines from healthy individuals. Peak 2'-5'OAS activity correlated with maximal titers of endogenous human interferon-alpha (HuIFN-alpha); (r = 0.80). Enzyme activity levels could be increased by treating LCLs with exogenous HuIFN-alpha, or decreased by neutralization of endogenous interferon with antibody to HuIFN-alpha. 2'-5'OAS activity always peaked during log-phase growth, even in cultures depleted of interferon by antibody and in cultures which did not produce interferon. Thus, although peak levels of 2'-5'OAS activity in a given LCL correlated with maximal interferon titers, the growth phase associated variations in enzyme activity were independent of interferon. We conclude that regulation of constitutive levels of 2'-5'OAS in LCLs is partially independent of interferon.

Infectious mononucleosis: sequential immunologic, cytochemical, and cytokinetic studies on single lymphoid cells in peripheral blood

Sequential immunologic, cytochemical, and cytokinetic studies were done on single lymphoid cells in the peripheral blood of 6 children with infectious mononucleosis (IM) and 1 child with toxoplasmosis 1-2 wk after onset of symptomatology. The absolute number of AET-SRBC rosetting (E+) cells was increased in all patients; the absolute number of cells with surface IgM (slgM+) was increased in 3 of 7 patients. On the average, 46% of all lymphoid cells were E+la+slgM-, 35% E+la-slgM-, and 5% E-la+slgM+. Of the E+la+slgM- cells, only 7% were shown to have a dot-like esterase reaction pattern. Of the E+la-slgM-cells, 17% were esterase positive. The mean labeling index of the former was 18.2%, the mean labeling index of the latter 4.4%. No proliferating slgM+ cells were observed in the 6 children with IM. The esterase reactions and the labeling indices of suppressor-cytotoxic and inducer-helper T cells were similar to those of E+la+slgM- and E+la-slgM- cells, respectively. These results suggest that the vast majority of the atypical cells in IM corresponds to activated suppressor cells, while a minority appears to be proliferating helper cells.

Hepatic function in mononucleosis induced by Epstein-Barr virus and cytomegalovirus

We evaluated serial enzyme and bilirubin determinations as aids to diagnosis of Epstein-Barr virus-induced infectious mononucleosis (121 cases) and the heterophil-negative mononucleosis-like illness due to cytomegalovirus (33 cases). Laboratory evidence for either type of mononucleosis includes mild to moderate hepatic dysfunction, with aspartate aminotransferase activity increased, but lower than commonly encountered in active viral hepatitis. Of the enzymes commonly assayed in evaluating liver function, aspartate aminotransferase activity was the most commonly abnormal: in 96.7% of those with Epstein-Barr virus disease and 87.9% with cytomegalovirus disease. Values for alkaline phosphatase were increased in 94.2% of the Epstein-Barr virus cases and 63.6% of the cytomegalovirus cases, and gamma-glutamyltransferase values were increased in 90.9% and 75.8%, respectively. We conclude that, in serially studied patients, normal results for liver-function studies or very high aspartate aminotransferase activities (greater than 1000 U/L) eliminate, for practical purposes, both Epstein-Barr virus and cytomegalovirus as diagnostic considerations.

Impaired T lymphocyte colony formation in infectious mononucleosis: evidence for both monocyte and lymphocyte defects

PHA-induced T lymphocyte colony formation in semi-solid agar culture was studied in mononuclear cells (MC) and non-adherent cells (NAC) from the blood of patients with infectious mononucleosis (IM). Colony formation expressed as number of colonies per 10(6) E-RFC or as number of colonies per ml of blood was depressed by about 90% during the first weeks of disease, but returned to normal levels during the convalescence period. Addition to the agar culture of conditioned medium prepared from adherent blood MC or normal donors partly restored colony formation by both MC andNAC from patients with IM in the acute stages, suggesting a subnormal production of conditioning factors by cocultured adherent cells. In line with this finding adherent cells from patients with acute disease failed to produce a conditioned medium which optimally supported the growth of T lymphocyte colonies from NAC of normal donors. When mononuclear cells from patients with IM were mixed with normal donor lymphocytes prior to agar seeding, colony formation by the normal cells was reduced by 10--65%. It is concluded that mononuclear cells from patients with IM have a reduced capacity to form T lymphocyte colonies in agar medium. This reduction possibly reflects a lack of production of colony stimulating factors from monocytes, but also increased activity of T lymphocyte colony suppressor cells.

Drug metabolism in liver disease. Identification of patients with impaired hepatic drug metabolism

Antipyrine half-life (AP t1/2) was measured in 62 patients with, and 10 control patients without, liver disease to ascertain possible factors which may be useful in identifying patients with abnormal drug metabolism. Antipyrine metabolism was normal or marginally impaired in patients with compensated cirrhosis or acute hepatitis, whereas it was frequently abnormal in those with chronic active hepatitis or advanced alcoholic liver disease. A high degree of correlation was found among AP t1/2 and prothrombin time, hepatic encephalopathy, and ascites. Of patients with severely impaired drug metabolism, 80% had one or more of these features. The severity of histological changes in liver biopsies was of additional help in predicting impaired drug metabolism. Concurrent drug ingestion enhanced antipyrine metabolism in most patients with liver disease as well as in control patients. Inadequate diet was associated with prolongation of AP t1/2, but other environmental factors such as alcohol ingestion, cigarette smoking, and coffee consumption did not affect rates of drug metabolism in patients with liver disease. Consideration of all of the above factors allows qualitative predictions of the rate of hepatic drug metabolism in patients with liver disease, as assessed by the AP t1/2.

Renal disease in infectious mononucleosis

Evidence of mild renal involvement is present in approximately 16% of patients with infectious mononucleosis as gauged by abnormalities in urinary sediment. Serious renal involvement including renal failure is very rare, our incidence was only 1.6%. There are only six cases reported in the literature during the last 25 years. The mechanism of renal involvement is probably multifactorial and includes both a direct viral cytopathic effect with other factors including hemolysis, hyperuricemia, and nephrotoxic drugs playing an important role. Interstital nephritis is the most common histologic abnormality. Chronic renal failure has been reported in only one case of infectious mononucleosis.

Human leukaemic cells. Determination of trace elements in nucleic acids and histones by neutron-activation analyses

Trace metals were measured by neutron-activation analyses in purified nucleic acids and histone(s) of lymphocytes from patients with acute lymphocytic leukaemia or infectious mononucleosis and from normal donor DNA isolated from lymphocytes of a patient with infectious mononucleosis and a normal donor showed a high a high content of Cr2+, Sb2+, Fe2+, and Zn2+, whereas DNA of lymphoblasts from a patient with acute lymphocytic leukaemia had a lower content of these trace metals, but the Co2+ content was 20-fold higher than in DNA or normal donor lymphocytic cells. Total histones from leukaemic cells had higher contents of most of the trace metals except for Zn2+, which was present in lesser concentration than in histones from normal donor lymphocytic cells. Lysine-rich (F1) histones showed lower contents of Cr2+, Sb2+ and Co2+, whereas arginine-rich (F3) histones had significantly higher contents of these trace metals. These observations may be of interest in that F3 histones more effectively inhibit RNA synthesis in human lymphocytic cells than do other species of histones.

Properties of chromosomal proteins of human leukemic cells

Purified chromatin isolated from lymphocytic cells derived from patients with acute leukemia, or other lymphoproliferative disorders has been compared with chromatin isolated from normal human lymphocytic cells by gel electrophoresis and differential gradient ultracentrifugation. Thermal denaturation studies showed higher Tm values for chromatin from leukemic cells, as compared to that of lymphocytic cells from normal donors or patients with infectious mononucleosis, reflecting the diverse complexity of these chromatins with respect to their varying chemical compositions. There are significant differences in the ratios of DNA:RNA:protein, as well as in the ratios of chromatin-associated histone and non-histone proteins; although chromatin-associated histones were more homogeneous than were the non-histone proteins, as adjudged by amino acid analyses and acrylamide gel electrophoresis. These differences in chromatin structure may relate to the differences in gene expression characteristic of these lymphocytic cells. The chromosomal acidic proteins isolated from the purified chromatin of human leukemic cells greatly stimulated the template activity of the chromatin in in vitro RNA synthesis. The non-histone proteins selectively interact with chromatins and influence the RNA polymerase reactions, indicating that there is selective tissue specificity of non-histone proteins.

Burkitt's tumors contain particles encapsulating RNA-instructed DNA polymerase and high molecular weight virus-related RNA

Burkitt's lymphomas, linked by previous studies with the DNA-containing Epstein-Barr virus, contain an RNA related in sequence to that of Rauscher leukemia virus. The present study establishes that the viral-related RNA found in Burkitt's tumors is a 70S component encapsulated with RNA-instructed DNA polymerase in a particle possessing a density characteristic of RNA tumor viruses. Further, the DNA synthesized by the Burkitt particles hybridizes specifically to the RNA of Rauscher leukemia virus. Thus, four features characteristic of a known oncogenic RNA agent are also exhibited by particles found with a high (87%) frequency in Burkitt's tumors. The relation between the RNA particle and the Epstein-Barr virus and their etiological roles remains to be elucidated. However, relevant to these issues is the finding reported here that the presence of Epstein-Barr virus information in nonneoplastic cells does not lead to the production of the RNA particles that have been detected now in three different human neoplasias, including leukemias, breast cancer, and Burkitt's disease.