Immune-derived cytokines in the nervous system: epigenetic instructive signals or neuropathogenic mediators?

The investigation of the effects of inflammatory cytokines (IC) on the growth and differentiation of neural cells has provided new insights on the role of such soluble mediators in nervous system development and/or plastic remodeling as well as in the pathogenesis of inflammatory neurodegenerative disorders, which are characterized by chronic IC dysregulation in the central nervous system (CNS). Thus, the study of the interaction between CNS and immune-derived soluble signals in physiological or pathological conditions is of increasing interest. This review first discusses experimental evidence supporting the instructive/permissive role of immune-derived cytokines on CNS development and plasticity. Next, we focus on human neurological disease states such as multiple sclerosis and the neurodegeneration associated to the acquired immune deficiency syndrome in which different inflammatory cytokines have been proposed as potential neuropathogenic mediators.

Biology of Kaposi's sarcoma.

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in several different clinical-epidemiological forms that, however, share the same histological traits and are all associated with infection by the human herpesvirus 8 (HHV8). KS initiates in a context of immune dysregulation characterised by CD8+ T cell activation and the production of Th1-type cytokines that induce a generalised activation of endothelial cells leading to adhesion and tissue extravasation of lympho-monocytes, spindle cell formation and angiogenesis. These phenomena are triggered or enhanced by infection with HHV8 that, in turn, is reactivated by the same cytokines. Productively-infected circulating cells are recruited into 'activated' tissue sites where HHV8 finds an optimal environment for establishing a persistent, latent infection of KS spindle cells (KSC). HHV8 dissemination is favoured by virus escape mechanisms and immune dysregulation, and leads to immune responses that are not effective against the virus but, paradoxically, exacerbates the reactive process. Although early KS is a reactive process of polyclonal nature that can regress, in time it can progress in to a true sarcoma. The progression of KS appears to be due to the deregulated expression of oncogenes and oncosuppressor genes, to the long-lasting expression of the HHV8 latency genes and, for AIDS-KS, is promoted by the proliferative and angiogenic effects of the HIV-1 Tat protein.

Distribution of the natural killer-related receptor for HLA-C during highly active antiretroviral therapy for human immunodeficiency virus infection.

Receptors interacting with Major Histocompatibility Complex class I molecules have been initially found on the surface of human natural killer (NK) cells, where they deliver inhibitory signals to the lysis, being thus defined killer inhibitory receptors (KIR). Subsequently, they were detected also on the surface of T-CD8(+) lymphocytes and are particularly expanded during human immunodeficiency virus (HIV) infection, where they downregulate HIV-specific cytolysis. The expression of KIR recognizing human leukocyte antigen-C alleles was assessed in HIV-infected patients, undergoing highly active antiretroviral therapy (HAART). To this end, the combined expression of CD16/CD56, of CD3 and CD8 as well as of KIR (CD158a and CD158b) surface molecules was analyzed on peripheral blood mononuclear cells by monoclonal antibodies, and flow cytometry. An increase of CD3(+)CD8(+)CD158b(+) cells was found after 6 months of HAART. This finding may have implications for the regulation of T-cell mediated cytolysis during HAART.

Activity of azelaic acid on cultures of lymphoma- and leukemia-derived cell lines, normal resting and stimulated lymphocytes and 3T3 fibroblasts.

Azelaic acid (C9- -dicarboxylic acid) is a competitive inhibitor of tyrosinase and some oxidoreductase in vitro, and in vivo has a beneficial effect on lentigo maligna and malignant melanoma. A definite cytotoxic effect in cultures of malignant melanocytes was also reported. In order to establish if the cytotoxic effect of the diacid is exerted equally in the absence of tyrosinase, lymphoma- and leukemia-derived cell lines were cultured for 72 hr with 10(-3) M, 10(-2) M and 5 X 10(-2) M C9 disodium salt. Normal resting lymphocytes, lymphocytes activated by phytohemoagglutinin, and mouse Balb/c 3T3 fibroblasts were also tested to study a possible effect of azelaic acid on DNA synthesis and cell duplication. At 10(-3) M C9 had no effect on the viability of all the cells tested; at 10(-2) M and 5 X 10(-2) M, C9 2Na had a 50-80% cytotoxic effect on lymphoma- and leukemia-derived cell lines, while at the same concentrations it was not toxic to normal lymphocytes, either resting or stimulated, or to 3T3 fibroblasts. The experiments on cellular incorporation of (1-9 14C) azelaic acid showed that the radiocarbon uptake was two to three times higher for lymphoma- and leukemia-derived cell lines than for lymphocytes, either resting or stimulated, or 3T3 fibroblasts. Biochemical analysis revealed that the diacid underwent beta-oxidation in all the cell cultures. Fractionated centrifugations of 3T3 fibroblasts cultured in the presence of radiolabelled azelaic acid (2 X 10(-4) M) plus cold C9 2Na (10(-2) M), showed that the radioactivity was mainly concentrated in the cytoplasm. The results, being similar to those obtained by adding azelaic acid to cultures of melanoma cells, suggest that the cytotoxic effect of azelaic acid may be due to interference with mitochondrial oxido-reductase enzymes, rather than with tyrosinase. The difference in reaction between lymphoma- and leukemia-derived cell lines and normal or stimulated lymphocytes, and 3T3 fibroblasts, could be explained on the basis of a different degree of permeability of the cell membrane, and/or to a possible different sensitivity of reaction of mitochondrial functions. A similar argument could be used to explain the absence of an effect of dicarboxylic acids upon normal as compared with hyperactive or malignant melanocytes in vivo.

Deficiency of natural killer activity, but not of natural killer binding, in patients with lymphoadenopathy syndrome positive for antibodies to HTLV-III.

Blood lymphocytes (BL) of eleven patients with lymphoadenopathy syndrome (LAS) were studied for natural killer (NK) activity against the K562 cell line (using both the standard 51Cr release assay and the single-cell cytotoxicity assay on poly-L-lysine-coated coverslips) and for surface phenotype (employing OKT4, OKT8 and Leu7 monoclonal antibodies). A significant reduction in NK activity and in NK active cells was detected, while the percentage of target binding cells was not affected. Furthermore, the OKT4/OKT8 ratio was found to be inverted, and the Leu7+ subpopulation expanded. The patients had high titers of anti-HTLV-III antibodies. This study indicates that defective NK activity in LAS is secondary to an abnormality in the lytic event itself and not in target binding.

Inhibitory effect of somatostatin-14 and some analogues on human natural killer cell activity.

The effect of somatostatin-14 (SST) and the SST analogues SMS and RC160 on human natural killer (NK) activity mediated by large granular lymphocytes (LGL), as well as on IL-2- and/or anti-CD16 monoclonal antibody (mAb)-induced activation of these cells, was investigated. The NK activity of LGL was studied by the release of 51Cr by the erythroleukemia-derived cell line K562, whereas 51Cr release by the P815 murine mastocytoma-derived cell line, for which lysis was redirected by the use of an anti-CD16 mAb, was used to study the cytolytic potential of these cells. IL-2 was used at the final concentration of 100 IU and was incubated overnight with LGL. SST and the analogues, added to these systems at final doses ranging from 10(-12) to 10(-5) M, were inhibitory of the NK cell activity to K562, with a dose-response curve starting from 10(-8) M and reaching a significant level at 10(-6) M. On the contrary, no effect was observed on the redirected killing assay to P815 and on the IL-2-induced activation of NK cells. These results provide additional evidence for the immunomodulatory action of somatostatin.

Modulation of human natural killer activity by vasoactive intestinal peptide (VIP) family. VIP, glucagon and GHRF specifically inhibit NK activity.

Vasoactive intestinal polypeptide (VIP) is a neuropeptide, which also modulates some immune functions. Natural killer (NK) cell activity was already found to be diminished by VIP. In the present paper we report that VIP is able to decrease NK cell activity of human large granular lymphocytes (LGL), showing maximal inhibition at doses ranging from 10(-8) to 10(-6) M. Some neuropeptides, belonging to the VIP family (secretin, glucagon, peptide histidine isoleucine, PHI and human growth hormone releasing factor, GHRF), were also tested. Among these peptides, secretin and PHI were shown to be uneffective on NK cell activity whereas glucagon and GHRF were inhibitory. The D50 of GHRF was similar to that of VIP (10(-9) M), the D50 of glucagon was 10(-8) M. A recently synthesized VIP-antagonist (4Cl-D-Phe6-Leu17) was then used to assess its ability to reverse the VIP-mediated inhibition of NK activity. The antagonist was able to completely reverse the inhibitory effect of VIP on NK activity. The VIP-antagonist was also able to reverse the inhibitory effect of glucagon and GHRF, even though to a lesser extent than for VIP. Our data provide a new physiological observation regarding the functional activity of LGL, supporting the presence of a receptor for VIP on human LGL with NK activity.

Herpes simplex virus vaccine in recurrent herpetic ocular infection.

PURPOSE: To evaluate the efficacy of an antiherpetic vaccine in recurrent herpetic ocular infections. METHODS: Twenty patients with herpes simplex virus 1-related recurrent keratitis/keratouveitis were prospectively enrolled and randomly assigned to receive either a specific vaccination with heat shock-inactivated herpes simplex virus type 1 (10 patients) or to be observed as controls (10 patients). The number, duration, and anatomic localization of relapses were recorded in all the patients for 12 months before inclusion in the study and for a similar period after the assignment of each subject to vaccine or control group. RESULTS: In the vaccine group, we observed a reduction both in the number (p = 0.016) and average duration (p = 0.050) of recurrences, whereas in the control group, no significant change was found comparing a 12-month period before and after inclusion in the study. The comparison between the two groups highlighted a significant reduction in the number (p = 0.013) and average duration (p = 0.051) of relapses in treated subjects, who did not show any significant vaccine-induced side effects. CONCLUSION: The use of a vaccination with heat shock-inactivated herpes simplex virus 1 seems to be able to reduce the number and duration of relapses in herpes simplex virus 1-related keratitis/keratouveitis.

Imbalance of the Epstein-Barr virus-host relationship in AIDS-related complex patients.

Patients affected by AIDS related-complex (ARC) showed several immunological abnormalities that could lead to a disregulation of immunosurveillance against viral latent infections. We report Epstein-Barr virus (EBV) reactivation was found in seven of eight ARC patients and in two of seven affected by persistent generalized lymphoadenopathy. These patients showed either elevated levels of circulating EBV-positive transformed cells and/or depressed EBV-specific T cell cytotoxicity as assessed by the regression assay. Natural killer cell activity was found to be decreased and correlated with evidence of circulating EBV-infected cells and with impaired EBV-specific immune control. Our data demonstrate that loss of control of EBV latency in the infected host by specific immune mechanisms increases the risk for EBV reactivation and emergence of clones with unlimited growth potential. A role of EBV as a cofactor in the development of ARC is suggested.

Kaposi's sarcoma pathogenesis: a link between immunology and tumor biology.

Kaposi's sarcoma (KS) was a rare disease in Europe and North America until a decade ago, when it became the most common neoplasm complicating the acquired immunodeficiency syndrome (AIDS), where it acquires an aggressive course. Clinical and experimental data suggest that, at least in early stage, KS may not be a true sarcoma, but an hyperplastic-proliferative lesion that may regress. At least three components characterize KS lesions: (1) neoangiogenesis and proliferation of spindle-shaped cells of endothelial and macrophage cell origin, some of which may originate from a circulating precursor; (2) a cellular infiltrate represented by macrophages, lymphoid cells, mast cells, and neutrophils; and (3) the infection of spindle cells and mononuclear cells with a new virus of the Herpesvirinae family defined KS-associated herpesvirus or human herpesvirus-8 (HHV-8). KS lesions are highly responsive, in terms of growth, to inflammatory cytokines (IC) and many lesional cell components are able to secrete cytokines and chemokines, which induce paracrine-autocrine mechanisms of growth, angiogenesis, and promote further cellular recruitment. The association between HHV-8 and KS is close; however, the role of the virus in KS development is yet unknown. Nevertheless, the virus has the potential to encode for homologs of cellular cytokines and some chemokines and its reactivation is sensitive to stimuli provided by IC. This review focuses on these aspects of KS pathogenesis, trying to reconcile many of the clinical and experimental observations. Finally, the role of the HIV-1 Tat protein as a factor of progression in AIDS-KS as well as the role of cellular and HHV-8 encoded proto-oncogenes as factors and markers of progression of KS to a true malignancy is reviewed.

Pathogenesis of the natural killer cell deficiency in AIDS.

Deficiency in natural killer (NK) cell activity is a common feature of acquired immune deficiency syndrome (AIDS). This is part of a general immune dysfunction in AIDS and may lead to progression of the disease, since NK cells are known to be involved in protection against tumors and against viral infections. The lack of immunological surveillance by NK cells of the growth of pathogens that activate the HIV-1 tat infectivity gene may also favor progression to AIDS. The pathogenesis of NK cell deficiency in AIDS is not known. Previous studies have shown that NK cells from AIDS patients are able to bind but not to lyse the target cell line K562. This results from an inability to rearrange the cytoskeleton microtubular (MT) system and to release the natural killer cytotoxic factor (NKCF). This report by Maria Caterina Sirianni and colleagues evaluates the possible mechanisms leading to this NK cell deficiency.

Protein A-positive staphylococci serve as a selective B cell mitogen for lymphocytes from primary immunodeficiency patients.

Staphylococcus aureus protein A-positive bacteria have recently been proposed as selective B lymphocyte mitogens. We have studied the lymphocyte response to such mitogens in bacteria in normal subjects and in patients with primary immunodeficiencies. Patients with primary T cell defects show a normal response to protein A-positive bacteria and impaired responses to PHA and Con A. In contrast, patients with Bruton agammaglobulinaemia respond normally to these T cell mitogens but not to the bacteria. Thus, protein A-positive bacteria fulfil the criteria for being a T cell-independent B cell mitogen for human peripheral blood cells.

House mite dust bronchial asthma: clinical and epidemiological observations.

The incidence of respiratory allergy in an adult population from Lazio is reported. A high prevalence rate of bronchial asthma was found, whereas the evolution of allergic rhinitis into bronchial asthma was less pronounced than that reported for childhood allergy. The mean age of onset of the symptoms was 15 +/- 5 years. A remarkable number of patients suffered from oculorhinitis, which resulted in bronchial asthma in a mean time of 5 +/- 3 years. Most of the patients came from Rome and were low-middle class. Previous history of possible co-factors in the development of respiratory allergies showed a high percentage of family atopy and of asthmatiform bronchitis. Studies of allergens responsible for disease revealed that house mite dust and Dermatophagoides are the major allergens responsible for the symptoms. An analysis of the most common therapy used for treating patients demonstrated a prevalence of anti-histamine, DSCG and chetotifen whereas cortisone treatment and hospitalization were less overspread. The present epidemiological survey shows a prevalence of adult onset bronchial asthma due to house mite dust. The importance of this observation in preventive medicine programmes is discussed.

Recurrent herpes genitalis, severe impairment of specific cell-mediated immune response and bilateral femoral head necrosis: report of a case.

The case of a 56 years old patient, affected by recurrent herpes genitalis (RHG) is reported. The patient came to our observation on March 1983 and he was suffering from RHG for 20 years, before our study. Episodes of RHG were severe, due to local and general symptomatology. Characterization of immune response showed decrease of NK activity to the K562 cell line, impairment of specific cell mediated immunity to Herpes simplex virus (HSV) as well as a decrease of T cells with helper phenotype. HSV type 2 was stained from active lesions. Immunological alterations were present irrespective of phase of activity of the disease during all the follow up period (March 1983-March 1985). At the first visit the patient was found to be suffering from a femoral head necrosis (FHN) of the right leg. One year later the same disease appeared at the contralateral leg. The possible relationship between RHG, accompanied by the described immunodeficiency, and the FHN is described.