Immune phenotype and prognosis in chronic B-lymphocytic leukaemia and leukaemic immunocytoma

Fifty-nine patients with a leukaemic B-lymphocytic malignancy ("CLL") were studied. According to the Kiel classification, 29 patients had chronic lymphocytic leukaemia (CLL) and 30 had immunocytoma (IC). Cell surface immunoglobulin staining showed mu heavy chain phenotype in 14 patients, mu in 35, gamma in 7; in cells from 3 patients the staining was too weak to permit identification. The light chain phenotype was kappa in 39 patients, lambda in 17, and unidentified in 3. The immunoglobulin isotypes differed between the diagnoses. The gamma chain phenotype was found only in IC patients (p less than 0.02), and more CLL than IC patients showed a lambda chain phenotype (p less than 0.04). Blood lymphocytes from IC patients contained more T cells than CLL cell samples (p less than 0.002). No prognostic difference was found between the CLL and IC group. Compared to the lambda phenotype, the kappa phenotype was associated with a poorer prognosis in the IC group, but with a better prognosis in the CLL group. IC patients with mu phenotype had a poorer prognosis than those with gamma phenotype. Low relative T cell numbers were associated with a poor survival (p less than 0.01).

Cushing's syndrome due to an ACTH-producing neuroendocrine tumour in the nasal roof

A patient with ectopic adrenocorticotrophic hormone (ACTH) production from a neuroendocrine tumour of the nasal roof is presented. By indirect immunoperoxidase techniques the tumour cells were shown to be distinctly positive for ACTH and beta-endorphin but negative for other peptides derived from pro-opiomelanocortin. Neither corticotropin releasing hormone (CRF) found in some tumours associated with ectopic Cushing's syndrome, nor gastrin immunoreactivity, which coexists with ACTH in normal rat pituitary and in rat and human gastrointestinal cells, were demonstrable in the tumour. A review of other, previously recognized locations of CRF/ACTH producing tumours is given to increase the awareness of the ectopic Cushing's syndrome, which may lack the classical features and is characterized by fulminant clinical course, extreme fatigue, weakness, pale facial swelling, oedema and hypokalaemic alkalosis.

Kaposi sarcoma-associated herpesvirus/human herpesvirus 8, cytokines, growth factors and HIV in pathogenesis of Kaposi's sarcoma

Epidemiological studies have strengthened the case for Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 being the long-sought Kaposi sarcoma agent, but have also pointed to a role for other co-factors. Like other tumour viruses, Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 establishes a latent (persistent) infection in Kaposi sarcoma-spindle (tumorous) cells, but can also undergo lytic replication in these and other cell types. Several latent and lytic viral genes may play a role in the pathogenesis of Kaposi's sarcoma. Although Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 contains at least two genes with transforming properties, it has not yet been shown to be oncogenic in animals. This, and other studies on inflammatory/angiogenic cellular and viral cytokines as well as HIV-Tat, emphasizes the multifactorial complexity of the pathogenesis of Kaposi's sarcoma.

Insulin-like growth factor-I receptor activity is essential for Kaposi's sarcoma growth and survival

Kaposi's sarcoma (KS) is a highly vascular tumour and is the most common neoplasm associated with human immunodeficiency virus (HIV-1) infection. Growth factors, in particular vascular endothelial growth factor (VEGF), have been shown to play an important role in its development. The role of insulin-like growth factors (IGFs) in the pathophysiology of different tumours led us to evaluate the role of IGF system in KS. The IGF-I receptors (IGF-IR) were identified by immunohistochemistry in biopsies taken from patients with different AIDS/HIV-related KS stages and on KSIMM cells (an established KS-derived cell line). Insulin-like growth factor-I is a growth factor for KSIMM cells with a maximum increase of ³H-thymidine incorporation of 130±27.6% (P<0.05) similar to that induced by VEGF and with which it is additive (281±13%) (P<0.05). Moreover, specific blockade of the receptor (either by α IR3 antibody or by picropodophyllin, a recently described selective IGF-IR tyrosine phosphorylation inhibitor) induced KSIMM apoptosis, suggesting that IGF-IR agonists (IGF-I and -II) mediate antiapoptotic signals for these cells. We were able to identify an autocrine loop essential for KSIMM cell survival in which IGF-II is the IGF-IR agonist secreted by the cells. In conclusion, IGF-I pathway inhibition is a promising therapeutical approach for KS tumours.

Dendritic cells in patients with non-progressive B-chronic lymphocytic leukaemia have a normal functional capability but abnormal cytokine pattern

Dendritic cells (DC) are attractive candidates for use in vaccine-based immunotherapy. We have analysed the functional capability of DC generated in vitro from blood CD14(+) cells of chronic lymphocytic leukaemia (CLL) patients and healthy donors by culturing for 10 d with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 4 (IL-4) and tumour necrosis factor-alpha (TNF-alpha). Two distinct DC populations were identified in patients as well as in controls. The majority of DC expressed CD11c and a minority also CD123. Most of the DC generated from both patients and controls exhibited a mature phenotype indicated by CD83 and major histocompatibility complex (MHC) class II expression, as well as by a characteristic morphology. Less than 1% of DC exhibited CD14. CLL DC had a similar expression of accessory molecules (CD54, CD80 and CD86) as control DC. The mean fluorescence intensity of CD80 and MHC class I molecules was significantly higher on CLL DC than on control DC (P < 0.05). At the gene level (real-time polymerase chain reaction) the expression of IL-10 was higher in CLL (P = 0.028) than in control DC. IL-1 beta and IL-12p(35) transcripts were also more abundant in CLL than in control DC but did not reach statistical significance. The expression of IL-4 and TNF-alpha was similar to that of control DC. The interferon gamma (IFN-gamma) gene expression level in CLL DC was decreased compared with control DC. DC of CLL patients had a similar capacity to stimulate in mixed leucocyte reaction as well as to present a recall antigen (PPD) as control DC. Thus, DC of CLL patients seem to have a normal function and may serve as antigen preserving cells for presentation of tumour antigens in a therapeutic vaccination approach. The mechanisms behind the observed increase in some surface molecules and the abnormal cytokine profile of CLL DC is not clear but might indicate pre-activation of DC in vivo, which may have a regulatory role in the pathobiology of CLL.

Immunohistochemical expression of extracellular matrix proteins and adhesion molecules in pancreatic carcinoma

BACKGROUND/AIMS

Carcinoma invasion and metastasis in general involve multiple steps including dynamic changes in the composition and structure of extracellular matrix proteins and cell surface receptors. In the present study, the usually highly invasive carcinoma of the pancreas was investigated regarding the expression of various extracellular matrix proteins and their corresponding integrin receptors, as well as E-cadherin.

METHODOLOGY

Phenotypic expression of various markers was investigated immunohistochemically in frozen sections of 16 pancreatic carcinomas and normal pancreatic tissue.

RESULTS

An irregular and discontinuous deposition of type IV collagen and laminin in the basement membrane was found in cancer tissue and a pronounced desmoplastic reaction with deposition of type I, type III, and type IV collagen in the tumor stroma. In contrast, the noninvolved pancreas showed an intact basement membrane and a sparse stroma. The collagen type IV and laminin receptors alpha 2, alpha 3, and beta 1 integrin subunits were expressed on pancreatic cancer cells but not the alpha 6 integrin subunit normally present on epithelial cells, suggesting anchorage independence of the carcinoma cells. An increased capacity for cancer cell motility was suggested by the abundant expression of the "antiadhesive" extracellular matrix proteins, tenascin and vitronectin close to the cancer cells, and the expression of cell surface receptors such as alpha v (vitronectin-binding). Expression of the alpha 4 integrin subunit was also increased on cancer cells.

CONCLUSIONS

The distribution of extracellular matrix proteins and the cell surface immune phenotype differed in pancreatic carcinoma as compared to normal pancreatic tissue. The present findings substantiate the notion that disseminated growth of highly malignant carcinomas of the pancreas reflects an invasive interaction of the tumor cells with extracellular matrix proteins of a well-established stroma. Similar findings were observed regardless of tumor histology and patient survival time.

Recombinant Semliki Forest virus vaccine vectors: the route of injection determines the localization of vector RNA and subsequent T cell response

Vectors based on Semliki Forest virus (SFV) have been widely used in vitro and in vivo to express heterologous genes in animal cells. In particular, the ability of recombinant SFV (rSFV) to elicit specific, protective immune responses in animal models suggests that rSFV may be used as a vaccine vehicle. In this study, we examined the distribution of rSFV in vivo by immunohistochemistry and RT-PCR after intravenous, intramuscular and subcutaneous injection of rSFV particles and related this to the degree of cytotoxic T lymphocyte (CTL) responses and frequency of specific T cells detected by MHC-I tetramers. We found that after i.v. injection, rSFV-RNA was distributed to a variety of different tissues, whereas it was confined locally after i.m. and s.c. injections. The persistence of the rSFV vector was transient, and no viral RNA could be detected 10 days after inoculation. All tested routes of immunization generated significant levels of antigen-specific CTL responses and increased numbers of specific CD8+ T cells, as detected by tetramer binding. The distribution of antigen-specific CTLs correlated with the in vivo distribution pattern of rSFV, with a highest frequency in the spleen or local lymph node, depending on the injection route.

Kaposi's sarcoma before and during a human immunodeficiency virus epidemic in Tanzanian children

BACKGROUND

With the onset of AIDS increased frequency of Kaposi's sarcoma (KS) has been reported. However, there is no case-based comparison of childhood (<14 years) KS before and during the HIV pandemic in sub-Saharan Africa. Here we report on the Tanzanian cancer registry data of pediatric KS in Tanzania and implications with regard to pathogenic factors.

METHODS

One hundred fifty histologically confirmed pediatric KS (PKS) cases registered during 1968 through 1995 (28 years) were analyzed with regard to demographic and clinical characteristics before and during the AIDS epidemic. Statistical analysis was done with the Epi-Info program and chi square test.

RESULTS

Of children with PKS 126 (84%) were male and 24 (16%) were female. The gender ratio was 5.1:1 and 5.4:1 during the endemic and epidemic periods, respectively. The highest occurrence of PKS was observed in the 0- to 5-years age group. Overall 73 (4.9/year) of these cases were registered during the pre and 77 (5.9/year) during the AIDS period. Over time a significant increase in anatomically disseminated KS cases was evident during the AIDS epidemic (P = 0.003).

CONCLUSIONS

These observations indicate that children younger than 5 years are at high risk for developing KS, possibly reflecting low resistance to human herpesvirus (HHV) 8 infection. It is also likely that an increased susceptibility to HHV8 infection and morbidity is related to progressive immunodeficiency. The increase in AIDS PKS incidence appears to reflect a direct or indirect promoting effect of HIV on the development of KS lesions. Recognition of the high KS risk in small children warrants considerations of possible prevention measures including HIV/HHV8 vaccination and therapeutic options.

Sequence analysis and variation of EBNA-1 in Epstein-Barr virus-related herpesvirus of cynomolgus monkey

OBJECTIVES

The Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1) is an important protein for immortalization and tumorigenesis of infected cells. EBNA-1 gene variants may play a role in tumorigenesis. We determined the nucleotide and amino acid (aa) sequences of EBNA-1 in EBV-related herpesviruses from cynomolgus monkeys (cynomolgus-EBV) which induced malignant lymphomas in its natural host and in rabbits, and compared them with sequences of EBV and other lymphocryptoviruses (LCVs).

METHODS

Polymerase chain reaction and direct sequencing methods were performed using extracted DNA from cynomolgus-EBV-infected cell lines.

RESULTS

The amino acid sequences of cynomolgus-EBV EBNA-1 from two cell lines (Si-IIA: 588 aa; Ts-B6: 619 aa) which are antigenically cross-reactive to human EBV EBNA-1 showed homology with human EBV (Si-IIA: 53%; Ts-B6: 58%) and other LCVs from baboons (54 and 52%) and rhesus monkeys (60 and 58%), especially in the C-terminal unique domain. Homology of the EBNA-1 sequence between Si-IIA and Ts-B6 was 92%. The sequence difference between EBV and the related LCVs was manifested mainly in the length of the internal repeat 3-corresponding region, which contains serine in the glycine/alanine repeat region of nonhuman LCVs.

CONCLUSION

Sequence variation of cynomolgus-EBV EBNA-1 from different cell lines was observed. However, their sequences show a relatively high homology with human EBV and share the common features of EBNA-1 of EBV and other LCVs.

Antibodies to human herpesvirus 8 latent and lytic antigens in blood donors and potential high-risk groups in Sweden: variable frequencies found in a multicenter serological study

Human herpesvirus 8 (HHV-8) is a herpesvirus associated with Kaposi's sarcoma (KS). An immunofluorescence assay was used for detection of IgG, IgM, and IgA antibodies against lytic and latent HHV-8 antigens to analyse samples from KS patients (n = 8), healthy blood donors (n = 162), individuals with a high risk sexual behaviour (n = 114), and bone marrow transplant patients (with high risk for bloodborne infections) (n = 34) in Sweden. Of the KS patients, 88% had IgG antibodies to both lytic and latent antigens by immunofluorescence. In all other groups, antilatent antibodies were rare (0-2.6%). IgG antibodies to the lytic antigens were found, by immunofluorescence, in 20% of the blood donors, 31% of the high risk patients, and in 24 and 29% of the bone marrow transplant patients (pre- and post-transplant samples, respectively). For verification of the specificity of the anti-lytic antibodies, 170 of the samples were also tested blindly at different laboratories world-wide with five other assays shown previously to detect HHV-8 antibodies in most KS patients. By using two recombinant HHV-8 proteins (ORF65/vp17 and K8.1/gp 35-37) in ELISA, a whole-virion ELISA and two immunofluorescence assays confirmation of the reactivity against lytic viral antigens was sought. The comparison of the different methods suggested the K8.1 ELISA to be highly specific and also showed a good agreement between two of the immunofluorescence assays. However, generally there was a poor correlation for positive results, indicating the need of further methodological development.

The apoptotic v-cyclin-CDK6 complex phosphorylates and inactivates Bcl-2

v-cyclin encoded by Kaposi's sarcoma herpesvirus/human herpesvirus 8 (KSHV or HHV8) associates with cellular cyclin-dependent kinase 6 (CDK6) to form a kinase complex that promotes cell-cycle progression, but can also induce apoptosis in cells with high levels of CDK6. Here we show that whereas HHV8-encoded v-Bcl-2 protects against this apoptosis, cellular Bcl-2 has lost its anti-apoptotic potential as a result of an inactivating phosphorylation in its unstructured loop region. Moreover, we identify Bcl-2 as a new substrate for v-cyclin-CDK6 in vitro, and show that it is present in a complex with CDK6 in cell lysates. A Bcl-2 mutant with a S70A S87A double substitution in the loop region is not phosphorylated and provides resistance to apoptosis, indicating that inactivation of Bcl-2 by v-cyclin-CDK6 may be required for the observed apoptosis. Furthermore, the identification of phosphorylated Bcl-2 in HHV8-positive Kaposi's sarcoma indicates that HHV8-mediated interference with host apoptotic signalling pathways may encourage the development of Kaposi's sarcoma.

Proliferation and apoptosis in the evolution of endemic and acquired immunodeficiency syndrome-related Kaposi's sarcoma

Kaposi's sarcoma (KS) is a multifocal lesion that occurs predominantly in the skin, most frequently in people infected with HIV-1, and that evolves through early stages (patch and plaque) to a tumor-like late stage (nodular). Both, endemic African (EKS) and AIDS-associated (AKS) KS expressed human herpesvirus 8 (HHV-8) as shown by PCR. By immunohistochemistry the expression of cellular Bcl-2 and c-myc was confined in early stages of both EKS and AKS to relatively few endothelial cells (EC) whereas in nodular KS most of spindle cells (SC) strongly expressed both genes. CD40 was usually strongly expressed in SC at all KS stages as well as in EC of non-involved tissue whereas CD40L (CD154) was not demonstrable. Fas (CD95) was moderately to weakly expressed by SC whereas p53 and Waf-1 were found in less than 5% of the SC. In both AKS and EKS at nodular stage almost no apoptotic SC were detected. In most AKS and EKS low levels of cell proliferation were seen but AKS showed consistently higher values compared to EKS. All clinical types and stages of KS showed a diploid cellular DNA content by flow cytometric analysis of microselected lesions. Thus, we conclude that KS during evolution represents diploid, probably reactive, cell proliferation, which progressively increases the expression of strong cellular and also viral (HHV-8) antiapoptotic factors.

Combined analysis of DNA ploidy, proliferation, and apoptosis in paraffin-embedded cell material by flow cytometry

A flow cytometric assay was developed for correlated measurement of DNA content and apoptotic DNA strand breaks in cell nuclei of formalin-fixed, paraffin-embedded tissues. The assay allows a combined analysis of cell ploidy, proliferation, and apoptosis in sections of fixed paraffin-embedded archival or fresh tissue/cell specimens. It is based on (a) proteolytic release of cell nuclei from deparaffinized and rehydrated 90-microm thick sections of the fixed embedded specimen, (b) the inactivation of the protease, (c) FITC-labeling of DNA strand breaks by the terminal deoxynucleotidyl transferase (TdT)-mediated FITC-dUTP nick end-labeling (TUNEL) reaction, and (d) DNA staining with 4'6-diamidino-2-phenyleindole. The fluorescence was recorded with a double-beam flow cytometer equipped with a mercury arc lamp and an argon ion laser. Cytograms obtained with this assay correlated closely with those produced using nonembedded material from the same specimen. Furthermore, a significant correlation was found between flow cytometric analysis of apoptosis in cell nuclei released from paraffin blocks and conventional evaluation of TUNEL on (corresponding) sections (p < 0.001). Since necrotic cells can stain positively by TUNEL, the possibility to microscopically select nonnecrotic tumor regions for flow cytometric analysis is an important advantage of the assay.

Antibody spectrum against the viral transactivator protein in patients with human immunodeficiency virus type 1 infection and Kaposi's sarcoma

We analyzed patterns of antibody response to recombinant transactivator protein (human Immunodeficiency virus type 1 [HIV-1] tat) in serum samples from HIV-1-negative subjects (n = 60), HIV-1-infected asymptomatic patients (n = 20), HIV-1-infected patients with Kaposi's sarcoma (n = 25), and patients with Kaposi's sarcoma without HIV-1 infection. None of the healthy subjects possessed anti-tat immunoglobulin G (IgG) in their serum. All asymptomatic patients with HIV-1 infection were anti-tat IgG-positive. Epitope mapping revealed that these sera had anti-tat IgG to all the functional domains of tat protein. Histochemical studies on lymph nodes from five asymptomatic HIV-1-infected patients showed that, in all cases, tat-positive cells were present within the germinal center at the stage of follicular fragmentation containing immunoblasts and small lymphocytes. Of the 25 HIV-1-infected patients with Kaposi's sarcoma, 4 were anti-tat IgG-positive; however, the epitope analysis revealed that IgG to functional domains of tat protein--in particular to transactivating response element (TAR)-binding site--were absent. All patients with Kaposi's sarcoma without HIV-1 infection were anti-tat IgG-negative. Presence or absence of anti-tat IgG and a prevalence of different antibody profiles in different groups of patients indicated the pathophysiologic role of tat protein. Thus, a passive immunization with anti-tat IgG could be a useful strategy to influence the pathophysiologic state of the disease.

Anti-CD3 induced thymocyte apoptosis in vivo require the antibody Fc domain

We have earlier found that explanted thymic epithelial cells (TEC) can produce glucocorticoid (GC) activity in vitro and that the GC receptor (GR) antagonist RU486 partially inhibit thymic apoptosis induced by the anti-CD3 monoclonal antibodies (MoAb) 2C11, both in vivo and in new-born thymic organ cultures. To explain the inhibitory effect of RU486 in this system we have now investigated the importance of the 2C11 Fc as this MoAb bind with high affinity to cellular FcR. We have found both that whole 2C11 MoAb can bind to explanted TEC in vitro and that F(ab)'2 fragments from this MoAb loose this ability, in addition with the capacity to induce thymic apoptosis in vivo. We interpret our results to indicate that the injected 2C11 MoAb may establish a close contact between GC producing, FcR positive TEC cells and CD3 positive thymocytes and thereby subject the later to high paracrine GC concentrations and subsequent induction of apoptosis.

Recruitment of monocyte derived dendritic cells ex vivo from SIV infected and non-infected cynomolgus monkeys

This study shows that characteristic dendritic, antigen presenting cells, can be generated from adherent peripheral blood mononuclear cells (PBMC)/monocytes of uninfected and SIVsm-infected cynomolgus monkeys after stimulation in vitro with granulocyte macrophage colony stimulating factor (GM-CSF) and interleukin (IL)-4. The recruitment of monocyte derived dendritic cells (MDDC) was usually possible irrespective of the level of immunodeficiency (CD4-level) and viremia. The cynomolgus MDDC closely resembled their human counterpart (immature MDDC) with regard to capacity to upregulate CD1a, CD40, CD86 and human leukocyte antigen (HLA)-DR and develop dendrites and veiled processes. Such MDDC also increased their capacity for antigen uptake (dextran endocytoses/macropinocytosis) and for induction of T-cell proliferation in mixed leukocyte reaction (MLR) assays. However, although no clear difference with regard to phenotype and morphology was seen between MDDC from SIV-infected and uninfected monkeys, a reduction in MLR responsiveness in MDDC from SIV infected monkeys was consistently detected within each experiment.

Epstein-Barr virus expression in Hodgkin's disease in relation to patient characteristics, serum factors and blood lymphocyte function

Epstein-Barr virus (EBV) expression was investigated by immunohistochemistry (latent membrane protein 1 [LMP-1]) and in situ hybridization (EBV encoded RNA [EBER]) in biopsies from 95 patients with untreated Hodgkin's disease (HD). Tumour EBV status was related to EBV antibody titres, spontaneous and concanavalin A induced blood lymphocyte DNA synthesis, serum levels of soluble (s) CD4, sCD8, sCD25, sCD30, sCD54, beta2-microglobulin, thymidine-kinase, routine chemistry, patient characteristics, complete remission and survival. The median follow-up time was 145 months (range 60-257). Tumour EBV-positive (n = 30; 33%) and negative (n = 62; 67%) patients did not differ with regard to sex, age, stage, presence of bulky disease or B-symptoms, remission rate or survival. The proportion of EBV+ cases was significantly higher among patients with mixed cellularity histopathology (58%) as compared to the nodular sclerosis subtype (18%; P < 0.001). The total white blood cell (WBC) counts were significantly lower in EBV+ patients (P < 0.01), who also had significantly higher levels of sCD54 (P < 0.02) and a tendency towards lower levels of sCD30 (P = 0.056). Patients in the tumour EBV+ group had significantly higher IgG antibody titres to restricted early antigen (EA-R) (P < 0.02). Hence, clinical features and outcome were not related to tumour EBV status. However, HD patients with EBV+ tumours had elevated sCD54 levels, higher antibody titres to EA-R and decreased total WBC counts. A potential causal relationship between EBV tumour status and these findings needs to be further explored.

Detection of distinct patterns of anti-tat antibodies in HIV-infected individuals with or without Kaposi's sarcoma

Patterns of antibody response to recombinant transactivator protein (HIV-1 tat) in serum samples from HIV-1-negative persons (n = 60), HIV-1-infected asymptomatic persons (n = 20), HIV-1-infected people with Kaposi's sarcoma (n = 25) and of people with Kaposi's sarcoma without HIV-1 infection have been analyzed. None of the healthy people had anti-tat IgG in their serum. All asymptomatic patients with HIV-1 infection were anti-tat IgG-positive. Epitope mapping revealed that these sera have anti-tat IgG to all the functional domains of tat protein. Four of the 25 HIV-1-infected patients with Kaposi's sarcoma were anti-tat IgG-positive; however, epitope analysis revealed that IgG to functional domains of tat protein, in particular to TAR-binding site, were absent. All patients with Kaposi's sarcoma without HIV-1 infection were anti-tat IgG-negative. Presence or absence of anti-tat IgG, and prevalence of different antibody profiles in different groups of patients suggest the pathophysiologic role of tat protein. Thus, a passive immunization with anti-tat IgG could be a useful strategy to influence the pathophysiologic state of the disease.

Expression of K13/v-FLIP gene of human herpesvirus 8 and apoptosis in Kaposi's sarcoma spindle cells

BACKGROUND

Human herpesvirus 8 (HHV8) infection is associated with all forms of Kaposi's sarcoma (KS). The HHV8 genome locus ORFK13-72-73 (ORF = open reading frame) encodes proteins that may be important in HHV8-mediated pathogenesis, i.e., the latency-associated nuclear antigen (encoded by ORF73), viral-cyc-D (v-cyc-D), a viral homologue of cellular cyclin D (encoded by ORF72), and viral-FLIP (v-FLIP), a homologue of the cellular FLICE (Fas-associated death domain-like interleukin 1 beta-converting enzyme) inhibitory protein (encoded by ORFK13; is an inhibitor of apoptosis [programmed cell death]). Through differential splicing events, this locus expresses individual RNA transcripts that encode all three proteins (tricistronic transcripts) or just two of them (v-FLIP and v-cyc-D; bicistronic transcripts). We examined expression of these transcripts in KS tissues.

METHODS

We collected tissues from patients with KS of different stages. By use of an optimized in situ hybridization procedure, we examined different ORFK13-72-73 locus transcripts in HHV8-infected cells in skin lesions and in one adjacent lymph node. Apoptosis in KS lesions was determined by use of an in situ assay.

RESULTS AND CONCLUSIONS

Our results indicate the following: 1) Transcripts from the ORFK13-72-73 locus appear to be spliced differentially in latently infected KS cells in skin lesions and in HHV8-infected cells in lymph nodes; specifically, ORFK13-ORF72 bicistronic transcripts were expressed abundantly in KS cells, whereas ORFK13-ORF72-ORF73 tricistronic transcripts were detected only in lymph node cells. 2) Sequences encoding the antiapoptotic protein v-FLIP are expressed at very low levels in early KS lesions, but expression increases dramatically in late-stage lesions. 3) The increase in expression of v-FLIP-encoding transcripts is associated with a reduction in apoptosis in KS lesions.

IMPLICATIONS

These data suggest that functional v-FLIP is produced in vivo and that antiapoptotic mechanisms may be involved in the rapid growth of KS lesions, where only a few cells undergoing mitosis are generally observed.

Kaposi's sarcoma-associated herpesvirus-encoded v-cyclin triggers apoptosis in cells with high levels of cyclin-dependent kinase 6

Kaposi's sarcoma-associated herpesvirus (KSHV) has a key etiological role in development of Kaposi's sarcoma (KS). v-Cyclin is a KSHV-encoded homologue to D-type cyclins that associates with cellular cyclin-dependent kinase 6 (CDK6). v-Cyclin promotes S-phase entry of quiescent cells and has been suggested to execute functions of both D- and E-type cyclins. In this study, expression of v-cyclin in cells with elevated levels of CDK6 led to apoptotic cell death after the cells entered S phase. The cell death required the kinase activity of CDK6 because cells expressing a kinase-deficient form of CDK6 did not undergo apoptosis upon v-cyclin expression. Studies on the mechanisms involved in this caspase-3-mediated apoptosis indicated that it was independent of cellular p53 or pRb status, and it was not suppressed by Bcl-2. In contrast, the KSHV-encoded v-Bcl-2 efficiently suppressed v-cyclin-/CDK6-induced apoptosis, demonstrating a marked difference in the antiapoptotic properties of c-Bcl-2 and v-Bcl-2. In KS lesions, high CDK6 expression was confined to a subset of cells, some of which displayed signs of apoptosis. These results suggest that v-cyclin may exert both growth-promoting and apoptotic functions in KS, depending on factors regulating CDK6 and v-Bcl-2 levels.

A cytotoxic, apoptotic, low-molecular weight factor from pineal gland

Previous studies suggest that the pineal gland may play a role in tumour growth inhibition. In this respect, melatonin, as the major hormone of this gland, has been extensively studied. However, there is growing evidence for the existence of other yet unknown pineal factors that may have tumour growth inhibiting properties. Here we describe the partial purification of a highly cytotoxic low molecular weight (<400 Da) hydrophilic fraction (designated F2M3R), starting from a porcine pineal extract (PE), via methanol precipitation followed by reverse-phase HPLC. F2M3R is cytotoxic for a highly apoptosis-resistant human erythroleukemia cell line (K562) at a concentration as low as 30 microg/ml. The viability of the cells was not influenced by an identical prepared porcine pituitary extract or by melatonin. PE induces apoptosis in K562 cells as indicated by three different criteria: morphology, in situ TUNEL assay and bi-parametric FACS analysis with annexin V and propidium iodide, but does not influence the viability of stimulated peripheral blood mononuclear cells. These observations warrant further purification and validation of the cytotoxicity in a panel of different human tumour and non-malignant cells.

Lymphoid disorders associated with HHV-8/KSHV infection: facts and contentions

Following the demonstration in 1994, that Kaposi's sarcoma (KS) was associated with a novel virus (KSHV or HHV-8) belonging to the lymphotropic herpes family, this virus was also found in certain lymphoid neoplasias of immunodeficient (HIV+) and immune competent hosts. The association of HHV-8/KSHV infection is now well established with primary effusion lymphoma (PEL) or body cavity based lymphoma (BCBL) and multicentric Castleman's disease (MCD) of the plasma cell type. A possible pathogenic role of HHV-8/KSHV in other lymphoid tumours including primary central nervous system lymphoma (PCNSL) and multiple myeloma (MM) as well as some atypical lymphoproliferations and sarcoidosis has also been suggested, but this is at present a controversial matter, or not confirmed. Several HHV-8/KSHV genes, including potential oncogenes, genes homologous to various cellular genes and growth factors have been incriminated in the pathogenesis of KS and PEL/BCBL, but a common pathogenic mechanism for the clearly diverse proliferations represented by PEL, MCD and KS is at present not evident.

Fetal porcine islet-like cell clusters transplanted to cynomolgus monkeys: an immunohistochemical study

BACKGROUND

The mechanism(s) involved in acute cellular xenograft rejection have hitherto been generated in vitro or in different experimental models, with pig tissue being transplanted to rodents. There is an urgent need to validate these results in a clinically more relevant combination of species.

METHODS

Fetal porcine islet-like cell clusters (ICC) were transplanted under the kidney capsule in cynomolgus monkeys, either untreated or given immunosuppression with cyclosporine (CsA; 10 mg/kg body weight, intramuscularly) and 15-deoxyspergualin (DSG; 5 mg/kg body weight, intramuscularly). ICC xenografts were examined at 1, 3, 6, or 10-12 days after transplantation, using immunohistochemical techniques. Serum levels of xenoreactive antibodies were measured with ELISA.

RESULTS

No deposits of IgM, IgG, Clq, or C3 were detected within the ICC xenograft in any of the monkeys. Likewise, no significant increase in the levels of xenoreactive antibodies were found after transplantation. In untreated animals, a few N-Elastase-positive cells (neutrophil granulocytes) were seen in the xenograft at day 1. A few mononuclear cells were present in the adjacent renal parenchyma, but they did not infiltrate the xenograft. At this time (day 1), early signs of necrosis were observed in the central parts of the graft. On day 3, the graft had a large, central necrotic area that contained polymorphonuclear cells; the remaining parts of the xenograft showed severe infiltration with CD8+ T cells. Occasional CD68+ cells (macrophages) were seen on days 1 and 3. On day 6, large numbers of macrophages were found infiltrating the entire graft. A few CD20+ B cells, accumulated as small clusters, were also found. Only a few natural killer cells (CD56+) were detected. The CsA/DSG-treated monkeys showed markedly fewer CD2+/CD8+ T cells on day 6 than the untreated monkeys, and the ICC graft was clearly better preserved. However, the number of CD8+ and CD68+ cells had increased considerably at 12 days after transplantation and diffusely infiltrated the whole ICC xenograft.

CONCLUSION

Porcine ICC transplanted under the kidney capsule in cynomolgus monkeys were rejected by an acute cell-mediated rejection progressing during the first 6 days after transplantation. The process was not dependent on host Ig or C3 binding to the graft. Although the rejection of porcine ICC was significantly delayed in CsA/DSG-treated monkeys, the ICC xenografts were almost completely destroyed 12 days after transplantation.

Proliferation and apoptosis-related gene expression in experimental acquired immunodeficiency syndrome-related simian lymphoma

Lymphomas in 10 cynomolgus monkeys infected with a simian immunodeficiency virus (SIVsm) were studied with regard to proliferative activity and apoptosis-related gene expression. All were diffuse large-cell lymphomas, showed mono or oligoclonality and a 9/10 diploid cellular DNA content. Expression of a simian homologue to Epstein-Barr virus (HVMF-1) was shown in nine cases. The lymphomas showed moderate to high proliferative activity by Ki67 immunostaining and DNA flow cytometry, and a low number of apoptotic cells detected by TdT-mediated dUTP nick-end labeling (TUNEL). Immunohistochemistry showed abundant tumor infiltrating TIA-1(+) cytotoxic lymphocytes (CTL) and macrophages. Bcl-2, Mcl-1, and also Bax and Bak, but not p53 were demonstrable in the tumor cells by immunostaining. Our findings suggest a causal relationship between HVMF-1 infection and a low apoptotic index of the lymphomas due to the expression of Bcl-2. The apparent inefficient function of tumor-infiltrating CTL could be due to inactivation of CTL and/or resistance of the lymphoma cells to CTL effects. The tumors showed immunoreactivity for CD18, CD29, and CD49d, but not for CD11a, mimicking the phenotype of human Epstein-Barr virus (EBV)-related lymphomas. In summary, our observations indicate a high similarity between this simian model of acquired immunodeficiency syndrome (AIDS)-related lymphomas (ARL) and human ARL and other immunosuppression-related lymphomas.

Immunopathology of metastases in patients of colorectal carcinoma treated with monoclonal antibody 17-1A and granulocyte macrophage colony-stimulating factor

Twenty patients with metastatic colorectal carcinoma were treated with a single infusion (400 mg) of a mouse monoclonal antibody (IgG2a) against the tumor-associated antigen CO 17-1A and with a daily injection of granulocyte macrophage colony-stimulating factor (GM-CSF) for 10 days. The cycle was repeated every month. Metastases from 5 of the 20 patients biopsied on days 1 and 10 of the first two treatment cycles were studied by immunohistochemistry. During treatment, neutrophils, monocytes, and T lymphocytes increased concordantly in the tumor as in the blood of the individual patient. Macrophages (CD68) and CD8+ T cells infiltrated the tumor glands and displayed TIA-1-reactive cytotoxic granules. Neutrophils were seen mainly in areas of necrosis. Activated (HLA-DR+) CD4+ T cells were usually abundant in the stroma. During treatment, few natural killer cells were found in the tumor, contrary to the marked increase seen in blood. Our observations indicate that GM-CSF markedly recruited activated, tumor-infiltrating leukocytes, possibly representing antibody-dependent cellular cytotoxicity and cytotoxic T effector cells. The notion that combined antibody and GM-CSF therapy may also promote a T-cell antitumor response is further supported and advocated by our findings. The study lends further support to combining GM-CSF with monoclonal antibody-based therapy.

Blood dendritic cells from myeloma patients are not infected with Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8)

In recent studies, the sequence of Kaposi's sarcoma-associated herpes virus (KSHV) or human herpes virus-8 (HHV-8) was detected in dendritic cells (DC) of patients with multiple myeloma (MM). A concern was raised whether there is an causal association between the viral infection and development of these tumors. In the present study, we have examined DC generated from blood adherent cells from 8 Swedish MM patients at different clinical stages and 2 patients with monoclonal gammopathy of undetermined significance. In addition, 6 myeloma cell lines and bone marrow cells from 2 MM patients were also studied. By polymerase chain reaction (PCR), including nested PCR, no virus DNA was demonstrable in the patients' DC or in myeloma cell lines or fresh bone marrow cells. Moreover, no antibody against KSHV was found in the serum of these 10 patients. Thus, our results indicate that blood-derived DC of MM patients in Sweden usually are not infected with KSHV/HHV-8. This study also suggests that KSHV/HHV-8 is not regularly associated with MM and consequently does not play a primary role in the pathogenesis of these tumors.

Immunological profile of endemic and epidemic Kaposi's sarcoma patients in Dar-es-Salaam, Tanzania

Kaposi's sarcoma (KS) presents in four clinicopathological types namely classical/sporadic (CKS), endemic African (EKS), iatrogenic (IKS) and that associated with AIDS (AKS). Recently a putative herpes virus (HHV-8) was described and shown to be present in all four types of KS. The immunological status of patients with EKS has been conflicting. In this study total leucocyte counts, total lymphocyte counts and lymphocyte subsets of patients with EKS and AKS were determined by flow cytometry and compared to those of healthy HIV-1 seronegative controls. Results show that 50% of EKS lesions were of nodular type. Patients with EKS had significantly lower levels of CD4+ T- lymphocytes and CD4:CD8 ratio but significantly higher CD8+ T-lymphocytes compared to controls. Patients with AKS had significantly lower levels of CD4+ T-lymphocytes and also CD4:CD8 ratios but significantly higher percentage of CD8+ T-lymphocytes when compared with EKS patients. These findings indicate that in both forms of KS there is a certain degree of immunological disturbance which is more conspicuous in AKS because of HIV infection and suggests that HIV-1 acts synergistically with the aetiological agent (HHV-8) to cause a more aggressive type of KS.

Trypanosoma cruzi infection in tumor necrosis factor receptor p55-deficient mice

Tumor necrosis factor receptor p55 (TNFRp55) mediates host resistance to several pathogens by allowing microbicidal activities of phagocytes. In the studies reported here, TNFRp55-/- mice infected with the intracellular parasite Trypanosoma cruzi showed clearly higher parasitemia and cumulative mortality than wild-type (WT) controls did. However, gamma interferon (IFN-gamma)-activated macrophages from TNFRp55-/- mice produced control levels of nitric oxide and killed the parasite efficiently in vitro. Trypanocidal mechanisms of nonphagocytic cells (myocardial fibroblasts) from both TNFRp55-/- and WT mice were also activated by IFN-gamma in a dose-dependent way. However, IFN-gamma-activated TNFRp55-/- nonphagocytes showed less effective killing of T. cruzi than WT control nonphagocytes, even when interleukin 1beta (IL-1beta) was added as a costimulator. In vivo, T. cruzi-infected TNFRp55-/- mice and WT mice released similar levels of NO and showed similar levels of IFN-gamma mRNA and inducible nitric oxide synthase mRNA in their tissues. Instead, increased susceptibility to T. cruzi of TNFRp55-/- mice was associated with reduced levels of parasite-specific immunoglobulin G (IgG) (but not IgM) antibodies during infection, which is probably linked to abnormal B-cell differentiation in secondary lymphoid tissues of the mutant mice. Surprisingly, T. cruzi-infected TNFRp55-/- mice showed increased inflammatory and necrotic lesions in several tissues, especially in skeletal muscles, indicating that TNFRp55 plays an important role in controlling the inflammatory process. Accordingly, levels of Mn2+ superoxide dismutase mRNA, a TNF-induced enzyme which protects the cell from the toxic effects of superoxide, were lower in mutant than in WT infected mice.

Measles virus antigen in macrophage/microglial cells and astrocytes of subacute sclerosing panencephalitis

In two patients with subacute sclerosing panencephalitis (SSPE) of 10 and 25 months duration we demonstrated by immunohistochemistry the presence of measles-virus nucleocapsid antigen (MVNA) in CD68+ cells and astrocytes of brain tissues. In both cases, CD68+ hematogenous monocyte/ macrophages and perivascular microglial cells (Mphi) were found infiltrating the brain parenchyma, and often partially or completely invested by perivascular reactive astrocytes expressing glial fibrillary acidic protein (GFAP). Mphi with cytoplasmic MVNA were often seen in the Virchow-Robin spaces and in close association with perivascular astrocytes, which often also contained MVNA+ intracytoplasmic inclusions. Reactive astrocytosis was more severe in the patient with long-standing illness, and a correspondingly elevated number of strongly GFAP+ MVNA+ or MVNA- perivascular binucleated astrocytes was observed. An uptake of MVNA+ cell debris by reactive astrocytes was evident in areas of white matter displaying extensive demyelination and necrosis. Taken together, these observations seem to indicate that the brain infiltration by Mphi carrying measles virus could represent one pathway of virus entry and dissemination in the central nervous system. Virus transfer to perivascular astrocytes via cell-to-cell contacts with infected macrophages is also suggested.

Intracerebral inflammation after human brain contusion

OBJECTIVE

This study was undertaken to analyze the inflammatory components in contused human brain tissue to compare the findings with previous experimental data regarding the pathogenesis of brain contusions.

METHODS

Contused brain tissue biopsies were obtained from 12 consecutive patients undergoing surgery for brain contusions 3 hours to 5 days after trauma. Inflammatory and immunological components were analyzed by immunohistochemistry.

RESULTS

In patients undergoing surgery less than 24 hours after trauma, the inflammatory response was limited to vascular margination of polymorphonuclear cells. In patients undergoing surgery 3 to 5 days after trauma, however, a massive inflammatory response consisting of monocytes/macrophages, reactive microglia, polymorphonuclear cells, and CD4- and CD8-positive T lymphocytes was detected. Human lymphocyte antigen-DQ was expressed on reactive microglia and infiltrating leukocytes in the late patient group. In addition, CD1a, which is a marker for antigen-presenting dendritic cells, was detected in a subgroup of microglial cells.

CONCLUSION

The results corroborated hypotheses derived from experimental data. In the early phase after contusional trauma, inflammation is mainly intravascular and dominated by polymorphonuclear cells. The inflammation was parenchymal in patients undergoing surgery 3 to 5 days after trauma. The brain swelling seemed to be biphasic, the delayed phase correlating with a parenchymal inflammation. The inflammatory cells may produce several potentially harmful effects, such as acute cellular degeneration; they may also lead to degenerative long-term effects.

Kaposi's sarcoma before and during the HIV epidemic in Tanzania

The Tanzania cancer registry recorded 39,920 cancer cases from 1968 to 1995. Kaposi's sarcoma (KS) constituted 4% of the cases of which 79.9% were males. During the AIDS period changes in the demographics of KS were noted showing an increase in the diagnosis of KS (p=0.0001). There was an overall decrease in the mean age from 41.7 years before to 37.3 years during the AIDS epidemic (p=0.002). In males this decreased from 42.7 to 38.8 years (p=0.01) but was not statistically significant in females (p=0.06). In both periods the cases were observed in the sexually active age groups. The narrowing of the male/female ratio during the AIDS period (p=0.0004), and an increase in extra-limb lesions from 19.7% before to 48.7% during the AIDS epidemic indicates the emergence of an aggressive form of KS in Tanzania, suggesting a co-factor role of HIV in KS pathogenesis.

Positive and negative thymic selection in T cell receptor-transgenic mice correlate with Nur77 mRNA expression

The orphan nuclear receptor Nur77 has been implicated in thymic negative selection. We studied the effect of two T cell receptor (TCR) transgenes on positive selection and Nur77 mRNA expression in thymus. DO11.10 mice, expressing a transgenic TCR specific for an ovalbumin (OVA) 323-339 peptide presented by I-Ad, were found to have an enlarged thymus with a reduced apoptotic activity, measured by flow cytometry, reduced mitochondrial membrane potential and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) techniques. In contrast, in F5 mice expressing a transgenic TCR recognizing the influenza virus nucleoprotein (NP) 366-374 peptide restricted by Db, this positive selection effect was much less pronounced. Positive thymic selection in DO11.10 TCR+ mice correlated with a reduced level of Nur77 mRNA expression shown by Northern blot. F5 mice expressed levels close to those expressed by the wild type. Both transgenic mouse strains responded with extensive cortical apoptosis, and with up-regulation of Nur77 mRNA, to injection of cognate peptides. As 9-cis-Retinoic acid (9-cis-RA) inhibits Nur77-dependent apoptosis in T cell hybridomas in vitro, mice were pretreated with the drug to investigate a similar effect in vivo. However, the drug itself, at saturating concentrations, caused extensive apoptosis in immature CD4+/CD8+ thymocytes. The result demonstrates a correlation between Nur77 expression and thymic apoptotic activity, both during positive and negative selection events.

Expression of HHV-8 latency-associated T0.7 RNA in spindle cells and endothelial cells of AIDS-associated, classical and African Kaposi's sarcoma

Analysis by polymerase chain reaction (PCR) and serological studies have demonstrated a close association between the novel human herpes virus, Kaposi's sarcoma-associated herpes virus (KSHV) or human herpes virus-8 (HHV-8) and the development of Kaposi's sarcoma (KS). To clarify the role of HHV-8 in KS pathogenesis, we investigated at the cellular level by in situ hybridization the expression of a recently described 0.7-kb HHV-8-encoded mRNA (T0.7 mRNA) in KS tissues of different epidemiological origin (AIDS-KS, African endemic KS and classical KS). The T0.7 mRNA likely encodes a small membrane protein, supposedly expressed in latently HHV-8-infected cells. Indeed, we detected T0.7 mRNA in virtually all cells of the cell line BCBL-1 established from a body cavity-based lymphoma (BCBL) and latently infected with HHV-8. In all KS biopsies examined, independent of their epidemiological type, the late-stage (nodular) KS tissues showed a high level of T0.7 mRNA expression in typical KS spindle cells but also in endothelial cells lining blood vessels, indicating latent HHV-8 infection of these cells. The presence of T0.7-expressing cells was restricted to KS tumor tissue and therefore appears to indicate an important role of latent HHV-8 infection in KS pathogenesis.

Endogenous fibronectin of blood polymorphonuclear leukocytes: immunochemical characterization and subcellular localization

Fibronectin, a large dimeric glycoprotein synthesized and secreted by several cell types, mediates cell adherence to surfaces. In infections and inflammatory responses, blood polymorphonuclear leukocytes (PMNs) adhere to cells and matrix proteins during extravasation and accumulation at inflammatory sites. The presence of fibronectin in blood PMNs has been poorly studied, and the characteristics and subcellular localization of this endogenous adhesive molecule are practically unknown. By immunofluorescence flow cytometry, purified rabbit antibodies and a monoclonal antibody to plasma fibronectin reacted with isolated blood PMNs, only after permeabilization of the cells. By Western blot analysis, the antibodies recognized, under reducing conditions, a protein with an apparent molecular mass of 230 kDa in the cell lysate. Eleven monoclonal antibodies to common frame fibronectin epitopes, including the RGD-containing cell-binding domain, also reacted with PMN fibronectin by Western blotting. In contrast, two antibodies to ED-A, the alternatively spliced region characteristic of "cellular" fibronectin, were unreactive, but recognized platelet fibronectin. On average, 1 million PMNs contained 6.8 ng +/- 1.4 (SD) of fibronectin, as measured by sandwich ELISA. Immunogold labeling and electron microscopy studies indicated localization of most fibronectin in PMN granules. Moreover, double-immunofluorescence and digital image analysis demonstrated colocalization of fibronectin with lactoferrin, a marker of specific (secondary) granules. The results indicate that blood PMNs contain approximately 8000 molecules per cell of intact ED-A-negative fibronectin localized mainly in their specific granules.

Intratumoral infusion of the monoclonal antibody, mAb 425, against the epidermal-growth-factor receptor in patients with advanced malignant glioma

Malignant glioblastoma may over-express the epidermal-growth-factor receptor (EGF-R). Normal brain cells show a low or no expression of EGF-R. A mouse monoclonal antibody (IgG2A) (mAb 425) (EMD55900) (Merck KGaA, Bernstadt, Germany) directed against EGF-R was produced for therapeutic use. Eight patients with primary or recurrent, EGF-R-positive glioblastomas entered the study, which was designed to evaluate the clinical effect of the mAb. In order to achieve a high tumor cell saturation, the mAb was injected intratumorally twice weekly through an implantable catheter. The total administered dose varied between 4 mg and 120 mg. In 3 patients with solid tumors, a massive tumor necrosis was noted, with infiltration of macrophages, granulocytes and T cells. A further 3 patients developed clinical and radiological signs of an intense, local, inflammatory reaction. There may be a relation between the mAb dosage and the antitumor effect, insofar as higher doses seemed to cause a more pronounced, inflammatory reaction. Of the 8 patients, 6 developed human, anti-(mouse Ig) antibodies. This anti-EGF-R mAb may induce an intense, inflammatory reaction and a considerable necrosis in glioblastoma. However, the planned schedule could not be completed, even after the dose level was re-adjusted, owing to inflammatory reactions, which were severe without prior tumor debulking.

European contribution to the science, prevention and management of HIV infection

The objectives of the European Commission Biomed AIDS Programme are to enable Europe to pool its intellectual and financial resources in the control, treatment and prevention of HIV infection and AIDS. In order to facilitate this aim the Commission has allocated 40 to 50 million ECU over the past 6 years for concerted action of the Biomed projects on AIDS by the countries of the European Union. This is only a small proportion of the real cost spent by the member countries on this epidemic.

Differentiation of human dendritic cells from monocytes in vitro

Since either macrophages (Mphi) or dendritic cells (DC) differentiate from monocytes (MO) depending on culture conditions, we investigated the relationship of the DC and Mphi differentiation pathways. Culturing MO-enriched blood mononuclear cells with Mphi colony-stimulating factor (M-CSF) or with granulocyte/Mphi (GM)-CSF induced Mphi with a different morphology and CD14/CD1a expression. In contrast, in cultures with GM-CSF and interleukin (IL)-4, cells rapidly became nonadherent and acquired DC morphology, ultrastructure, CD1a expression, and most DC markers; they lost membrane CD14 and CD64 and capacity of phagocytosis, displayed less CD68 than Mphi, but retained nonspecific esterase activity. These DC directly developed from MO without proliferation inasmuch as only day 0 FACS-sorted MO, but not small CD14- cells, differentiated into DC when cultured with GM-CSF and IL-4, or to Mphi with M-CSF While overall cell numbers declined, DC numbers plateaued from culture day 2 onwards, indicating that most had differentiasted by then. This differentiation was radioresistant and occurred without [3H]thymidine incorporation. Commitment to differentiate into DC with GM-CSF and IL-4 was irreversible by day 2, since discontinuing IL-4 at this point did not revert cells to Mphi. Alternatively, cells rapidly converted to DC when IL-4 was added from day 2 to cultures initiated with GM-CSF only. If cultures were initiated with M-CSF and switched to GM-CSF and IL-4 after 2 or 5 days, about half of the cells still converted to DC. Thus, the capacity of MO and even of Mphi to differentiate into DC was conserved for at least this period. The increased capacity to stimulate the mixed leukocyte reaction correlated with the relative number of CD1a+ cells at any time and under each condition tested, a confirmation that these cells functionally qualify as DC. Thus, MO and even Mphi can be directed to differentiate into DC depending on the cytokine microenvironment.

Intracellular co-localization of Trypanosoma cruzi and inducible nitric oxide synthase (iNOS): evidence for dual pathway of iNOS induction

Evidence is presented from studies in vitro and in vivo for a dual pathway of inducible nitric oxide synthase (iNOS) induction during Trypanosoma cruzi infection, one of which is interferon (IFN)-gamma dependent and the other not. In vitro, the IFN-gamma-dependent iNOS induction decreases parasite multiplication, and is in vivo associated with protection. iNOS induced by this pathway mediated a high NO output and showed a diffuse, cytoplasmic immunostaining in IFN-gamma-activated macrophages in vitro as well as in cell infiltrates or infected tissues. Surprisingly, in such tissues, iNOS co-localized with parasite nests, and by immunoelectromicroscopy, iNOS was demonstrated on the parasite surface. iNOS co-localization with parasites was also seen in tissues from T. cruzi-infected IFN-gamma receptor (R) knockout mice suggesting an IFN-gamma-independent pathway of induction. However, no cytoplasmic iNOS was seen in inflammatory infiltrates of these tissues. IFN-gammaR(-/-) mice displayed a dramatically enhanced susceptibility to infection with T. cruzi, diminished accumulation of iNOS mRNA in skeletal muscle and spleen cells, and reduced release of NO and peroxynitrite. Expression of iNOS around intracellular parasites was also observed after infection of peritoneal macrophages or L-929 fibroblasts in vitro in the absence of other exogenous stimuli. A time-dependent NO release and enhanced accumulation of iNOS mRNA also was observed in infected peritoneal cells and fibroblasts. Cultured T. cruzi amastigotes, trypomastigotes, and epimastigotes were not labeled by the anti-iNOS antibodies and contained no iNOS mRNA, indicating that the iNOS detected actually originated from the mammalian cell. A pathogenic effect of low NO levels is suggested by the arresting effect of NOS inhibitors and the enhancing consequences of low concentrations of NO donors on intracellular parasite multiplication.

Expression of adhesion molecules in endemic and epidemic Kaposi's sarcoma

Spindle cells and vascular endothelium in nodular lesions of AIDS associated (epidemic) and endemic Kaposi's sarcoma showed similar immunohistochemical patterns of expression for cell adhesion molecules and extracellular matrix proteins. Spindle cells as well as endothelium also expressed both alpha 5 and alpha V integrin subunits and ICAM-1 suggesting a possible role for inflammatory cytokines in spindle cell formation. The spindle cell compartment was rich in collagen, laminin, fibronectin and tenascin suggesting an important reactive component in the evolution of Kaposi's sarcoma. The lack of thrombospondin expression in the spindle cells favours the contention that they could be transitional, proliferating cells of endothelial origin. Specific expression of tat protein was not seen suggesting minimal if any HIV replication in these lesions. Our findings suggest similar histopathogenetic mechanisms for endemic and epidemic Kaposi's sarcoma. The clinically more malignant features of most AIDS related cases may reflect an important effect of systemic and focal cytokines in HIV patients and possibly other cofactor(s), i.e. tat protein in the induction and growth of the lesions.

Oncogenesis in HIV-infection

The presence of human Kaposi's sarcoma associated herpesvirus-like sequences (KSHV) was examined in different epidemiological variants of Kaposi's sarcoma (KS) and in KS-derived cell cultures by polymerase chain reaction (PCR). KSHV DNA was present in all tumor biopsies of AIDS-associated KS (59 biopsies), endemic KS (26 biopsies; 21 African endemic KS, 5 Greek endemic KS), sporadic/classical KS (28 biopsies) and post-transplant/iatrogenic KS (6 of 7 biopsies). On the contrary, these sequences were only detected rarely in non-involved skin of KS patients (3 positive specimens of 12), in the peripheral blood mononuclear cells of HIV-infected patients (3 positive specimens of 54) and in lymphoma-biopsies (3 positive specimens of 47). Cell cultures derived from KS skin lesions were positive for KSHV DNA only in the first two passages. However, two longer-term positive cultures from a biopsy of a patient affected with sporadic KS and a biopsy of a patient affected with epidemic KS was identified. A strong association of KSHV with KS tissue was observed in all the different epidemiological variants of KS. Long-term positive KS-derived cell cultures will be an important tool to study the herpesvirus-like agent and to investigate its functional role in the initiation and progression of KS.

Retrieval of leukocyte antigens in paraffin-embedded rat tissues

We compared the immunohistochemical reactivity of various rat leukocyte antigens in frozen and paraffin-embedded thymus, spleen, abdominal lymph node, liver, and brain tissues of healthy Sprague-Dawley rats, fixed in various fixatives. Immune reactivity after fixation in Methacarn was superior to that of 4% neutral buffered formalin, a mercury-based fixative (B-5), or Carnoy. Microwave (MW) antigen retrieval (AR) enhanced antigen reactivity. Ten of the 11 leukocyte antigens studied could be retrieved in Methacarn-fixed, paraffin-embedded sections with a reactivity comparable to that obtained on frozen sections.