Interleukin-2, autotolerance, and autoimmunity

The triggering of post-COVID-19 autoimmunity phenomena could be associated with both transient immunosuppression and an inappropriate form of immune reconstitution in susceptible individuals

With the progression of the COVID-19 pandemic, there have been different reports about the development of autoimmune diseases once the infection is controlled. After entering the respiratory epithelial cells, SARS-CoV-2—the virus that causes the disease—triggers a severe inflammatory state in some patients known as “cytokine storm” and the development of thrombotic phenomena—both conditions being associated with high mortality. Patients additionally present severe lymphopenia and, in some cases, complement consumption and autoantibody development. There is a normalization of lymphocytes once the infection is controlled. After this, autoimmune conditions of unknown etiology may occur. A hypothesis for the development of post-COVID-19 autoimmunity is proposed based on the consequences of both a transient immunosuppression (both of innate and acquired immunity) in which self-tolerance is lost and an inappropriate form of immune reconstitution that amplifies the process.

Nivolumab in Renal Cell Carcinoma: Current Trends and Future Perspectives

Targeted agents form the backbone of most therapeutic strategies in advanced renal cell carcinoma (aRCC) but ultimately resistance develops and toxicity often leads to discontinuation of treatment, limiting the clinical benefits of these treatments. Nivolumab, a fully human IgG4 anti-PD-1 antibody, selectively blocks the interaction between PD-1 and its ligands PD-L1 and PD-L2 and provides a novel therapy option for patients with aRCC. In 2015, the pivotal phase III study CheckMate 025 led to the Food and Drug Administration approval of nivolumab in patients with aRCC who had received prior anti-angiogenic therapy, and in 2017, the phase III study CheckMate 214 showed that combined immunotherapy with nivolumab plus ipilimumab resulted in greater objective response rate and prolonged progression-free survival when compared with sunitinib in intermediate- and poor-risk patients with previously untreated aRCC. Early studies of nivolumab in association with anti-angiogenic therapy have generated enthusiasm and multiple combination trials are ongoing.

Are soluble IL-2 receptor and IL-12p40 levels useful markers for diagnosis of tuberculous pleurisy?

BACKGROUND

The differential diagnostic utilities of the levels of soluble interleukin (IL)-12p40 and the IL-2 receptor in sera and pleural effusions were evaluated in patients with exudative pleural effusions.

METHODS

We enrolled a total of 120 patients with exudative pleural effusions. The clinical, radiological, and histopathological diagnoses were tuberculous pleurisy in 52, malignant pleurisy in 39, and parapneumonic effusions in 29 patients.

RESULTS

We measured serum IL-12p40 and adenosine deaminase (ADA) levels in patients with tuberculous pleurisy and in a control group treated for pleural effusion to determine if such levels were useful in the diagnosis of pleural effusion (p < 0.005). Definite microbiological or histopathological diagnoses of tuberculous pleurisy or pleural effusion were recorded, and we found that ADA and serum soluble IL-2 receptor levels aided in diagnosis (p < 0.001). The levels of ADA and soluble IL-2 in pleural effusions afforded sensitivities and specificities of 84.62% and 82.69% and of 70.59% and 80.88%, respectively. The soluble IL-2 receptor level afforded a sensitivity and specificity of 82.69% and 52.9%. IL-12p40 levels in pleural effusions and sera afforded sensitivities and specificities of 80.77% and 80.77% and of 60.29% and 39.71%, respectively.

CONCLUSION

Soluble IL-2 receptor levels in patients with tuberculous pleurisy serve as markers of disease in non-endemic countries, similarly to ADA levels.

Biological significance of soluble IL-2 receptor

A NUMBER of receptors for growth factors and differentiation antigens have been found to be secreted or released by cells. Following mononuclear cell (MNC) activation and interleukin-2 receptor (IL-2R) expression, a soluble form of the Alpha;-chain of IL-2R (sIL-2R) is released. The sIL-2R has been shown to be present in the culture supernatants of activated MNCs as well as in normal sera and, in higher amounts, in sera from subjects affected by several diseases including neoplastic, infectious and autoimmune ones, and in sera from transplanted patients suffering allograft rejection. The blood sIL-2R levels depend on the number of producing cells and the number of molecules per cell, so that sIL-2R blood values may represent an index of the number and the functional state of producing cells, both normal and neoplastic. Thus, monitoring of the immune system, mostly T-cells and haematological malignancies might be targets for the measurement of sIL-2R. Since many conditions may influence sIL-2R production, little diagnostic use may result from these measurements. However, since blood sIL-2R levels may correlate with disease progression and/or response to therapy, their measurement may be a useful index of activity and extent of disease. The precise biological role of the soluble form of the IL-2R is still a matter of debate. However, we know that increased sIL-2R levels may be observed in association with several immunological abnormalities and that sIL-2R is able to bind IL-2. It is conceivable then that in these conditions the excess sIL-2R released in vivo by activated lymphoid cells or by neoplastic cells may somehow regulate IL-2-dependent processes. On the other hand, it cannot exclude that sIL-2R is a by-product without biological significance. Finally, it is puzzling that in many conditions in which an increase of blood sIL-2R values has been observed, MNCs display a decreased in vitro capacity to produce sIL-2R. These seemingly contrasting findings are discussed in the light of the data showing that sIL-2R production correlates with IL-2 production.

Intracytoplasmic cytokine levels and neutrophil functions in early clinical stage of type 1 diabetes

Studies indicate that both CD4(+) and CD8(+) T lymphocytes and their cytokines play a critical role in different clinical stages of type 1 diabetes (T1D). Disturbances of oxidative burst and phagocytic activities in neutrophils of diabetic patients compared to uncontrolled disease support the importance of neutrophil functions in the treatment and follow up of diabetic patients. This study is designed in order to investigate Th1 and Th2 cytokine profiles and neutrophil functions in early clinical stage of T1D. Patients diagnosed as T1D but not yet under insulin therapy (Group 1; n=15) and T1D patients with disease duration of <3 months (Group 2; n=20) were compared to healthy subjects (Group 3; n=15). All subjects with T1D were positive for islet cell antibody (ICA) and glutamic acid decarboxylase antibody (GADA), their fasting glucose levels were >126 mg/dl and A1(c) levels were >8. Intracytoplasmic interleukin (IL)-2, IL-10, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha levels of isolated CD4(+) and CD8(+) T cells, and neutrophil functions were determined by flow cytometry. Intracellular TNF-alpha level of CD4(+) T lymphocytes was significantly decreased in Group 1 compared to Group 2 and healthy subjects. In contrast, TNF-alpha in CD8(+) T lymphocytes was higher in Group 1 compared to Group 2. Increased TNF-alpha content of CD8(+) T lymphocytes was also obtained in Groups 1 and 2 compared to healthy subjects. Increased TNF-alpha secretion of CD8(+) T cells might reflect the role of CD8(+) T cells in beta cell destruction. Similar to cytokine content, phagocytic and oxidative burst activities in Group 1 were significantly lower compared to Group 2 and healthy subjects. Impaired neutrophil functions could be recovered by the treatment of the disease.

A medical oncologist's approach to immunotherapy for advanced renal tumors: is nephrectomy indicated?

Metastatic renal cell carcinoma is highly resistant to systemic therapy. Although interleukin-2 and interferon remain the most active agents for this disease, long-term survival rates remain poor. Two phase 3 trials, European Organization Research and Treatment of Cancer 30947 and Southwest Oncology Group 8949, have demonstrated a survival benefit of nephrectomy followed by interferon versus interferon alone in patients having an excellent performance status (PS 0 and 1). Removal of the primary tumor followed by interferon is not recommended for patients with a moderate or poor PS (PS 2-4). Even with this aggressive approach, most patients eventually will die from their kidney cancer; therefore, every patient with metastatic disease should be considered for enrollment into clinical trials.

Review article: immunopathogenetic and therapeutic aspects of autoimmune hepatitis

Autoimmune hepatitis is a chronic, progressive liver disease that responds well to immunosuppressive therapy, but has a poor prognosis if untreated. Possible triggering factors include viruses, other autoimmune disorders and drugs. The molecular mechanisms contributing to the pathogenesis include: reactions of autoantibodies against their corresponding autoantigens; aberrant expression of histocompatibility antigen class I and II molecules, cell adhesion molecules and cytokines; increased oxidative stress; and the occurrence of angiogenesis. The prevalence of the disease is highest in Caucasians, Europeans and women. The natural history of autoimmune hepatitis shows a poor prognosis, with frequent progression to cirrhosis and hepatic insufficiency in untreated patients. The occurrence of hepatocellular carcinoma is rare and is found only in long-standing cirrhosis. Corticosteroids as monotherapy or in combination with azathioprine are the treatments of choice; different therapeutic schedules and particularities of treatment for pregnant women and children have been established. To avoid treatment-associated adverse effects, alternative therapies have been proposed, including ciclosporin, budesonide, tacrolimus, mycophenolate mofetil, ursodeoxycholic acid, methotrexate, cyclophosphamide, mercaptopurine and free radical scavengers. Liver transplantation is indicated for patients refractory to or intolerant of immunosuppressive therapy.

Elevated interleukin-2, interleukin-6 and interleukin-8 serum levels in neuroleptic-free schizophrenia: association with psychopathology

Cytokines have been one of the recent focal points of immunological research in schizophrenia. The present study was to assess the serum levels of some of interleukins in schizophrenia and their relationships with the psychopathological parameters. Seventy physically healthy Chinese patients, who met DSM-III-R criteria for schizophrenia and who were drug-free for at least 2 weeks, were compared with 30 age- and sex-matched Chinese normal controls. The psychopathology of schizophrenia was assessed by the Positive and Negative Syndrome Scale (PANSS). Serum levels of IL-6 and IL-8 were measured by sandwich enzyme-linked immunosorbent assay (ELISA), and serum IL-2 level was assayed by radioimmunometric assay (RIA). Serum levels of IL-2, IL-6 and IL-8 were significantly elevated in patients with a chronic form of schizophrenia (all p<0.05). There was a significant inverse relationship between IL-2 level and the PANSS positive subscale P (r=-0.31, p=0.006) and a significant positive correlation between IL-8 level and PANSS negative subscale N (r=0.25, p=0.036) in schizophrenic patients. In control subjects, a significant and positive relationship between serum IL-2 and IL-6 (r=0.513, p=0.004) was noted, whereas, there was a significant and negative relationship between IL-2 and IL-8 in schizophrenic patients (r=-0.28, p=0.02). Our data confirms and supports the view that immune disturbance is involved in schizophrenia, which is compatible with the possibility that Chinese schizophrenic patients have an ongoing autoimmune process. This immune disturbance is related to the subgroup of schizophrenic patients with characteristic clinical variables. The dysfunction of interaction or inter-adjustment between different cytokines may exist in schizophrenic patients.

Cytokine serum levels, autologous mixed lymphocyte reaction and surface marker analysis in never medicated and chronically medicated schizophrenic patients

A number of immunological parameters were studied in 82 DSM-III-R diagnosed schizophrenic patients (53 first drug-naive and 29 medicated chronic patients) as well as 62 healthy blood donors. The serum levels of interleukin-2 (IL-2), interleukin-1 beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) were measured and correlated with cellular immunity, as assessed by the autologous mixed lymphocyte reaction (AMLR). T lymphocyte subsets were also examined. The above immune parameters were reassessed in a subgroup of 11 first-episode, drug-naive patients 1month after neuroleptic medication. IL-2 serum levels were significantly lower, and IL-1beta and TNF-alpha were significantly higher in schizophrenic patients compared with healthy donors (P<0.001); no significant difference was observed between the two patient groups (medicated and not medicated). Abnormal cytokine serum levels were associated with decreased AMLR responses in vitro. Increased percentages of activated CD4+ and CD16+ natural killer cells, as well as cells expressing ICAM-1 adhesion molecules and IL-2 specific receptors, were detected in the patients. Immunophenotype studies revealed a higher percentage of cells expressing IL-2 receptors in medicated chronic schizophrenic patients compared with drug-naive patients. The abnormal cytokine production in vivo, along with the low AMLR responses in vitro, and the high percentage of activated CD4+ lymphocytes presented in this study suggest alterations in the immune system of schizophrenic patients (medicated or not medicated) consistent with immune activation.

Cytotoxic T lymphocytes versus streptococcal colonization in periapical granulomas

Seventeen dental periapical lesions were investigated to study bacterial colonization. Periapical lesions, obtained after apicotomy, were also enzymatically desegregated to quantitatively analyze lymphocyte subpopulations by flow cytometry. Fourteen samples yielded a positive bacterial growth when homogenized and cultured. We isolated enough lymphocytes to make flow cytometric analysis from 12 samples. A significant increase in interleukin-2 receptor and ICAM-1 molecule expression on T cells was found, compared with peripheral blood lymphocytes. Furthermore, a decreased expression of interleukin-2 receptors and HLA DR molecules on CD8+ T cells was found in granulomas predominantly colonized by Streptococcus spp., compared with lesions predominantly colonized by strict anaerobes.

Impaired Alloantigen-Mediated T Cell Apoptosis and Failure To Induce Long-Term Allograft Survival in IL-2-Deficient Mice

We examined whether IL-2 regulates alloimmune responses by studying allograft survival in wild-type (IL-2+/+) and IL-2 gene-knockout (IL-2−/−) mice. The acute rejection of vascularized, cardiac allografts and the generation of allospecific CTLs were not impaired in the absence of IL-2. In contrast, blocking the B7-CD28 T cell costimulation pathway with CTLA4Ig induced long-term allograft survival (&gt;100 days) in IL-2+/+ recipients but failed to do so in IL-2−/− mice or in wild-type mice that had been treated with IL-2-neutralizing Ab around the time of transplantation. Allografts rejected by IL-2−/− recipients exhibited extensive mononuclear cell infiltrates despite CTLA4Ig administration. In vivo allostimulation in the absence of IL-2 led to exaggerated T lymphocyte proliferation and impaired apoptosis of activated T cells in untreated and CTLA4Ig-treated mice. These findings indicate that endogenous IL-2 is required for the induction of long-term allograft survival, and that IL-2 regulates alloimmune responses by preparing activated T lymphocytes for alloantigen-induced apoptosis.

Interleukin-2 and systemic lupus erythematosus--fifteen years later

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.

Decreased interleukin-2 production in Korean schizophrenic patients

BACKGROUND

It has been postulated that autoimmune process may play a role in the pathogenesis of symptoms in some schizophrenic patients. Findings of altered interleukin (IL) regulation have been regarded as additional proof that schizophrenia has an autoimmunological background.

METHODS

Sixteen patients who fulfilled DSM-IV criteria for schizophrenia and who were drug free for at least six months and the same number of age- and sex-matched controls were recruited. The severity of symptoms in schizophrenia was assessed by BPRS. Phytohemagglutinin (PHA)-stimulated production and serum level of IL-1 beta, IL-2, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

There was a significant decrease of IL-2 production (p < .01) in schizophrenic patients and a significant increase of IL-2 serum level (p < .01). No significant difference of IL-1 beta and IL-6 was found. Some patients and controls had measurable serum level of IL-1 beta and IL-6. No significant correlation between production and serum level of IL-1 beta, -2, -6 and age, duration of illness, and BPRS score in schizophrenics was found.

CONCLUSIONS

This is the first study to describe a decrease of IL-2 production and increase of IL-2 serum level in non-Caucasian schizophrenic patients. These findings are further evidence that autoimmune process is present, regardless of ethnic origin, in some schizophrenic patients.

Natural history and therapy of metastatic renal cell carcinoma: the role of interleukin-2

BACKGROUND

Despite significant advances in understanding the biology of renal cell carcinoma (RCC) during the past decade, metastatic disease remains nearly incurable and a major medical challenge. Because RCC is known to be immunogenic, immunotherapeutic agents such as recombinant human interleukin-2 (rIL-2) and interferon-alpha (IFN-alpha) have represented encouraging treatment modalities.

METHODS

A review of the natural history of and therapeutic approaches to RCC was examined. Studies involving rIL-2 alone and in combination with other adjuvant therapies were critically evaluated.

RESULTS

Overall response rates for metastatic RCC patients treated with rIL-2 were similar (i.e., in the range of 15-20%), regardless of whether rIL-2 was administered as monotherapy or in combination with IFN-alpha. Recombinant IL-2 monotherapy response rates were similar to those of IFN-alpha, but with an increased frequency of complete responses and enhanced response duration. Subcutaneous administration generally resulted in lower toxicity than intravenous administration. The roles of chemotherapy or adoptive immunotherapy in combination with rIL-2 and IFN-alpha therapy remain unclear and require further study. The importance of patient performance status as a predictor of response and survival in rIL-2 therapy was demonstrated.

CONCLUSIONS

The use of rIL-2 with or without IFN-alpha may represent the most useful therapeutic approach currently available for patients with good performance status. In patients with borderline performance status or severe comorbid disease, therapeutic approaches depend on patient factors and outcome expectation and may involve cytokine therapy. However, regardless of performance status, palliative measures and/or observation are important choices, because the majority of patients with metastatic RCC are incurable.

Neurotoxicity induced by interleukin-2: involvement of infiltrating immune cells

Interleukin-2 (IL-2), a key regulator of immune functions, also has potent effects on neurons and glia. IL-2 modulates neural cell growth and survival and transmitter and hormone releases and is thought to mediate neuroimmune interactions. Investigating the neuroendocrine consequences of chronically elevated central nervous system (CNS) levels of IL-2, we recently observed marked neurotoxicity [Hanisch et al. (1994) Endocrinology 135:2465-2472]. In the present study, we characterize in detail the modifications in brain tissue architecture as they result in Sprague-Dawley rats from intracerebroventricular (i.c.v.) administration of low amounts of IL-2 (5 and 15 U/h, respectively, delivered by means of osmotic minipumps for up to 14 days). Histological inspection of the brains revealed massive cellular infiltrates in the ipsilateral hemisphere. The infiltrates were associated with pronounced angiogenesis and changes in the composition of the extracellular matrix. These anatomical changes apparently developed between day 7 and 14. They were specific for IL-2 and were not seen in animals treated, for example, with heat-inactivated IL-2 (controls). We further show that chronic central administration of IL-2 let to T and B lymphocyte invasion of the brain and an intracranial agglomeration of large numbers of MHC class II-positive cells. Immunocytochemistry revealed a widespread inundation of CNS tissue and a decoration of glial cells and neurons by endogenous antibodies. Tissue regions around the IL-2-induced infiltrates showed myelin destruction and neuronal cell loss. Chronically elevated CNS levels of IL-2 may, thus, not only interfere with neurotransmission and endocrine functions but also severely disturb tissue homeostasis. Therefore, the present findings could be relevant to brain injuries, CNS disorders, and clinical treatments associated with increased IL-2 levels or involving an immune component.

Aod2, the locus controlling development of atrophy in neonatal thymectomy-induced autoimmune ovarian dysgenesis, co-localizes with Il2, Fgfb, and Idd3

In genetically susceptible strains of mice, such as A/J and (C57BL/6J x A/J)F1 hybrids, neonatal thymectomy-induced autoimmune ovarian dysgenesis (AOD) is characterized by the development of antiovarian autoantibodies, oophoritis, and atrophy. Temporally, atrophy may be observed during and after the regression of inflammatory infiltrates from the ovary. Histologically, lesions appear as areas devoid of ovarian follicles in all stages of development that have been replaced by luteinized interstitial cells. We report here the mapping of Aod2, the locus that controls this phenotype, to mouse chromosomes 3 within a region encoding Il2 and Fgfb. Most significant, however, is the co-localization of Aod2 to Idd3, a susceptibility gene that plays a role in autoimmune insulin-dependent type 1 diabetes mellitus in the nonobese diabetic mouse.

Expression of CD45-restricted form B in (NZW x BXSB) F1 and MRL/Mp-lpr/lpr mice

Expression of CD45RB on CD4+ or CD8+ cells in combination with TCRV beta usages (V beta 6, V beta 8.1, V beta 8.2, V beta 11 and V beta 17a) in normal mouse strains (BALD/c and C57BL/6) was compared with autoimmune-prone strains (NZW x BXSB) F1 and MRL/lpr) at young and old ages. The frequencies, and also the numbers of CD45RB- cells in CD4+ T cells with various TcR repertoires was significantly less in the autoimmune-prone stains at old ages, while, in normal control strains, they remained unchanged. Furthermore, CD4+/CD45RB- cells are CD44high and CD62L (L- selectin).low These findings suggest that most T cells, especially CD4+ T cells, in old W/BF1 and old MRL/lpr mice, were activated and this may reflect the elevation of autoantibodies and the progress of autoimmune status in aged autoimmune-prone mice. This will be discussed in relation to the progress of the autoimmune diseases.

Differential involvement of Th1 and Th2 cytokines in autoimmune diseases

By virtue of their functional antagonism, Th1 cells or cells producing the same cytokines as Th1 cells may behave as "suppressor cells' with respect to Th2 cells and vice versa. An excessive Th1- or Th2-like response may favor the development of different autoimmune diseases. As can be expected from their physiological role, Th-1 cytokines participate in autoimmune diseases with a preferential delayed type hypersensitivity component, i.e. in those diseases in which cytotoxic T cells attack organ-specific target cells. Autoimmune diseases with a predominant Th1 component include experimental autoimmune encephalitis and insulin-dependent diabetes mellitus. In contrast, Th2-type responses participate in systemic autoimmune diseases with a strong humoral component. Such diseases probably include certain drug-induced states of autoaggression, namely mercury-induced autoimmune disease and chlorpromazine-induced autoimmunity. It is tempting to speculate that therapeutic interventions designed to recover a normal Th1/Th2 balance will provide a useful etiological strategy for the re-establishment of self-tolerance.

Transgenic/knockout mice--tools to study autoimmunity

Transgenic and knockout mice have been valuable tools for clarifying the roles of individual cell types and effector molecules in the pathogenesis of autoimmunity. During the past year, new strains have been added to the large array of transgenic mice, with broad or tissue-specific expression of transgene products. These laboratory models, as well as knockout mice lacking genes for a particular molecule, have greatly enhanced our understanding of autoimmune disease.

Interleukin-2 as a neuroregulatory cytokine

Interleukin-2 (IL-2), the cytokine also known as T-cell growth factor, has multiple immunoregulatory functions and biological properties not only related to T-cells. In the past decade, substantial evidence accumulated to suggest that IL-2 is also a modulator of neural and neuroendocrine functions. First, extremely potent effects of IL-2 on neural cells were discovered, including activities related to cell growth and survival, transmitter and hormone release and the modulation of bioelectric activities. IL-2 may be involved in the regulation of sleep and arousal, memory function, locomotion and the modulation of the neuroendocrine axis. Second, the concept that IL-2 could act as a neuroregulatory cytokine has been supported by reports on the presence in rodent and human brain tissues of IL-2-like bioactivity, IL-2-like immunoreactivity, IL-2-like mRNA, IL-2 binding sites, IL-2 receptor (IL-2R alpha) and beta chain mRNA and IL-2R immunoreactivity. IL-2 and/or IL-2R molecules mainly localize to the frontal cortex, septum, striatum, hippocampal formation, hypothalamus, locus coeruleus, cerebellum, the pituitary and fiber tracts, such as the corpus callosum, where they are likely expressed by both neuronal and glial cells. Although the molecular biology of the brain IL-2/IL-2R system (including its relation to IL-15/IL-15R alpha) is not yet fully established by cloning and complete sequencing of all respective components, similarities (and to some extent differences) to peripheral counterparts are now apparent. The ability of IL-2 to readily penetrate the blood-brain barrier further suggests that this cytokine could regulate interactions between peripheral tissues and the central nervous system. Taken together, these data suggest that IL-2 of either immune and CNS origin can have access to functional IL-2R molecules on neurons and glia under normal conditions. Additionally, dysregulation of the IL-2/IL-2 receptor system could lead or contribute to functional and pathological alterations in the brain as in the immune system. Understanding the neurobiology of the IL-2/IL-2 receptor system should also help to explain neurologic, neuropsychiatric and neuroendocrine side effects occurring during IL-2 treatment of peripheral and brain tumors. Immunopharmacological manipulation either aiming at the activation or suppression of IL-2 signaling should consider functional interference with constitutive and inducible IL-2 receptors on brain cells in order to fulfil the high expectations associated with the use of this cytokine as a promising agent in immunotherapies, especially of brain tumors.

Pertussis toxin-sensitive GTP-binding proteins regulate activation-induced apoptotic cell death of human natural killer cells

Apoptosis of natural killer (NK) cells can be induced by non-specific physical damage (UV irradiation, heat shock) or by simultaneous ligation of the CD16 and the interleukin-2 receptor (IL-2R) molecules, but not with either anti-CD16 or IL-2 alone. Whereas blockade of GTP-binding protein (G protein)-mediated signal transduction using ADP-ribosylating bacterial toxins or the GTPase-resistant GTP analog guanosine 5'-0-(3-thiotriphosphate (GTP gamma S) does not affect non-specific induction of NK cell apoptosis, such interventions do inhibit induction of apoptosis by anti-CD16/IL-2. The G proteins involved in the regulation of activation-induced NK apoptosis are sensitive to pertussis toxin (PTX) and to the non-specific GTP analog GTP gamma S but not to cholera toxin, Pseudomonas exotoxin A or diphtheria toxin. A pertussis toxin mutant that lacks ADP-ribosylating activity, but conserves the membrane translocating and T cell-mitogenic effects of the native molecule, fails to inhibit NK apoptosis. To exert their apoptosis-inhibitory effect, PTX and GTP gamma S must be employed before cells are activated. Later addition has no effect, suggesting the implication of G proteins in the transmission of apoptosis-inducing signals, but not in the effector stage of apoptosis. Pre-incubation with PTX or GTP gamma S does not affect the activation of NK cells by CD16 cross-linking, IL-2 stimulation- or both, as assessed by the induction of CD69 expression, protein tyrosine phosphorylation and calcium mobilization. Moreover, neither PTX nor GTP gamma S compromise the effector function of NK cells or the susceptibility of target cells to NK-mediated lysis. These data suggest apoptosis as a novel mechanism by which NK responses may be controlled in vivo, as well as an experimental and therapeutical strategy to counteract endogenous down-regulation of NK responses.

Defective production of interleukin-2 in patients with idiopathic Parkinson's disease

The pathogenesis of Parkinson's disease (PD) is largely unknown. Recently, several studies have presented evidence of an immunological dysfunction in patients suffering from PD. We studied the immune responsiveness of patients with idiopathic PD (n = 20) by investigation of the ability of peripheral blood mononuclear cells to produce cytokines after mitogenic stimulation in a whole blood assay. A group of age-related healthy blood donors served as control (n = 19). Additionally, white blood count, leukocyte differentiation and lymphocyte subtyping were performed. PD patients had a significantly higher neutrophil count, but analysis of T-cell subsets showed no difference between the two groups. In peripheral blood, secretion of interleukin-2 (IL-2) after mitogenic stimulation was significantly diminished in the patients' group (p < 0.01), whereas values of IFN-alpha 2, IL-6, IFN-gamma and sIL-2R were comparable in both groups. IL-2 production correlated negatively with the mean annual dose of levodopa treatment and correlated significantly (p < 0.002) with amantadine uptake. Analysis of sex, age, duration of illness and other drug intake revealed no correlation with cytokine release. Our findings support the view that there is a selective abnormality in the immune repertoire of peripheral blood lymphocytes in patients suffering from PD, the reasons for which need to be explored.

Dysregulation of T helper cell cytokines in autoimmune prone NZB x NZW F1 mice

Multifactorial involvement in the pathogenesis of autoimmune NZB/W F1 mice has been well documented. To further elucidate the role of cytokines in the disease development of murine lupus, single spleen cells isolated from NZB/W F1 and non-autoimmune C57BL/6 mice were stimulated with T cell mitogens or anti-CD3 antibody at pre-determined optimal concentration. Supernatants were collected and assayed for production of cytokines including IL-2, gamma-IFN, IL-3, IL-4, IL-5 and IL-10. In both young and old mice, cytokine profiles by mitogen-stimulated T cells showed higher TH2 (type 2 T helper) cell-related cytokine production in NZB/W F1 mice compared to those in non-autoimmune C57BL/6 mice. In contrast, cytokines produced by TH1 (type 1 T helper) cells, such as gamma-IFN and IL-2, were lower in NZB/W F1 mice by stimulation with either mitogen or anti-CD3 antibody. In addition, cytokine production at different time points also demonstrated decreased gamma-IFN and increased IL-4 levels by anti-CD3 stimulated splenic cells in autoimmune NZB/W F1 mice. Furthermore, the IL-10 levels produced by lipopolysaccharide (LPS)-stimulated splenic and peritoneal exudate cells were higher in young NZB/W F1 mice compared to those in C57BL/6 mice. Our data suggest that dysregulation between TH1 and TH2 cells may play an important role in the pathogenesis of autoimmunity in NZB/W F1 mice.

T-cell activation in HLA-B8, DR3-positive individuals. Early antigen expression defect in vitro

The HLA-B8, DR3 haplotype is overrepresented in several autoimmune diseases, implying that genes predisposing to these disorders are linked to this haplotype. In the patients affected by these diseases, as well as in healthy HLA-B8, DR3 individuals, various dysfunctions reflecting an impairment of T-cell activation have been found. To better characterize T-cell impairment of HLA-B8, DR3-positive healthy individuals, we analyzed the surface expression of early (CD69) and late (CD71) activation phenotypes. MNC cultures were stimulated with PHA and used for T-cell phenotyping by flow cytometry analysis. The results showed that the percentage of CD69+ T cells was significantly decreased in MNC from HLA-B8, DR3+ subjects. This defect was detected in cell cultures from all subjects studied, but it attained significance only in females in the early hours after stimulation. The difference in CD69 expression between HLA-B8, DR3-positive individuals and -negative ones was not due to differences in CD4 and CD8 ratios in the HLA-B8, DR3 cells that underwent activation, as following activation the pattern of CD4 and CD8 antigen expression was the same in both groups of subjects. Concerning the late antigen CD71, no significant difference in percentage was observed between T lymphocytes from HLA-B8, DR3+ and HLA-B8, DR3- subjects at all the times studied. The analysis of the requirements for CD69 expression has suggested that sustained PKC activation and an increase of intracellular CA2+ could be responsible for TCR/CD3-mediated CD69 induction. Thus, present data suggest a defect in the signal transduction pathway of the TCR/CD3 complex.(ABSTRACT TRUNCATED AT 250 WORDS)

The isolation and sequence of canine interleukin-2

A cDNA corresponding to canine IL-2 has been isolated and sequenced. The cDNA was synthesised using RT-PCR, with oligonucleotide primers designed from conserved regions of published IL-2 sequences. The cDNA encodes a predicted full length IL-2 protein of 155 amino-acids. At the nucleic acid level, the canine cDNA shows 92, 88, 88, 82 and 74% homology to published sequences of feline, human, equine, bovine and murine IL-2, respectively. The derived protein shows 90, 86, 85, 76 and 75% similarity to feline, human, equine, murine and bovine IL-2 homologs.

Apoptosis, Fas and systemic autoimmunity: the MRL-lpr/lpr model

Proteins encoded by the fas and fas ligand (fasL) genes are involved in apoptotic cell death in lymphocytes. In this article we review the recent elucidation of the role of the Fas-FasL interactions in the maintenance of tolerance to self antigens and in the homeostatic regulation of lymphocyte clonal expansion, and discuss the mechanisms of autoimmunity in Fas- and FasL-deficient mutant mouse strains.

Drugs recently associated with lupus syndromes

A number of drugs have recently been implicated in a syndrome that resembles systemic lupus erythematosus. One of the difficulties in many of these patients is that the signs, symptoms and serological abnormalities reported in these patients may be a natural consequence of the primary diseases rather than the incriminated drug. A second problem with the studies is a lack of uniform reporting of the techniques used to detect autoantibodies. For example, a patient that has a highly positive ANA with a homogeneous pattern of staining or a positive LE cell test usually has antibodies directed against chromatin components (DNA, histones, high mobility group (HMG) proteins). The discrepancies in clinical criteria and the serological techniques in many of these reports, emphasize the importance of using guidelines for the diagnosis of drug-induced or drug-related lupus. In the future, it appears that the increased use of biological response modifiers such as interferon-alpha and other cytokines may prompt more reports of lupus syndromes associated with their use.

Interleukin-10 inhibits apoptotic cell death in infectious mononucleosis T cells

T lymphocytes from patients with acute EBV-induced infectious mononucleosis rapidly die by apoptosis in vitro. Because human and viral IL-10 are likely to be induced during acute EBV infection and display a variety of functions on human T cells, we examined IL-10 effects on infectious mononucleosis T cell death. After 12 h of incubation in medium alone, only 35.6 (+/- 8.2%) of the originally seeded infectious mononucleosis T cells were viable. Addition of human IL-10 (100 U/ml) to T cell cultures significantly improved recovery of viable cells (71.3 +/- 6.2%, P = 0.0156). Viral IL-10 had comparable effects to human IL-10 in this system. Protection from death by human and viral IL-10 (100 U/ml) was dose dependent and continued over a 6-d culture period. The human IL-10 effect was neutralized by the anti-human IL-10 mAb 19F1. Morphology and analysis of DNA after separation on agarose gels showed that IL-10 inhibits loss of cell volume, chromatin condensation, and DNA fragmentation, characteristics of death by apoptosis. As assessed by [3H]thymidine incorporation, the T cells were not induced to proliferate by IL-10 above the level exhibited when first removed from blood. T cells protected from death by IL-10 proliferated to IL-2 and spontaneously killed sensitive targets as effectively as medium-precultured T cells. Thus, IL-10 promotes the survival of infectious mononucleosis T cells otherwise destined to die by apoptosis and may be critical for the establishment of immunologic memory after resolution of the illness.

Costimulator B7-1 confers antigen-presenting-cell function to parenchymal tissue and in conjunction with tumor necrosis factor alpha leads to autoimmunity in transgenic mice

Tolerance to peripheral antigens is thought to result from the inability of parenchymal tissue to stimulate T cells--an inability that is believed to relate to the lack of expression of the costimulatory signal(s) required for T-cell activation. To test this model, we generated transgenic mice expressing costimulatory molecule B7-1 on the B cells of the pancreas. We find that islets from these transgenic mice are immunogenic for naive T cells in vitro and in vivo. Nonetheless, mice expressing the costimulator B7-1 specifically on beta cells do not develop diabetes, suggesting that expression of the B7-1 costimulator is not sufficient to abrogate the tolerance to peripheral antigens. We have reported that tumor necrosis factor alpha subunit (TNF-alpha) expressed by beta cells leads to a local inflammation but no islet destruction. Strikingly, however, the combination of a local inflammation due to the expression of the cytokine TNF-alpha and the expression of B7-1 results in tissue destruction and diabetes.

Defective T cell receptor/CD3 complex signaling in human type I diabetes

The autoimmune process leading to the destruction of pancreatic beta-cells is mediated by T lymphocytes. Peripheral T cells from subjects with preclinical and clinical type I diabetes respond weakly in vitro to lectin stimulation. We, therefore, investigated in a group of newly diagnosed diabetic patients the presence of a defect in the signal transduction pathway of the T cell receptor (TcR)/CD3 complex. Following stimulation with anti-CD3-coupled beads, the proliferative response in diabetic T cells was significantly decreased in comparison with that from normal T cells. Interestingly, addition of either recombinant interleukin (IL)-2 or phorbol 12-myristate 13-acetate to the cell culture was able to completely restore impaired anti-CD3-induced proliferation in diabetic T cells, suggesting the presence of a defect through the TcR/CD3 pathway, located upstream of protein kinase C (PKC) activation and resulting in low IL-2 production and proliferation. Intracellular Ca2+ measurements by Fluo-3 labeling and flow cytometry analysis on diabetic and control T cells after anti-CD3 stimulation gave comparable results, indicating that this defect does not involve events leading to intracellular Ca2+ mobilization. In contrast, anti-CD3 stimulation of diabetic T cells resulted in a marked impairment of PKC translocation and CD69 antigen expression, as assessed by peptide substrate phosphorylation and by flow cytometry analysis, respectively. Taken together, our data clearly show the presence in individuals at the onset of the disease of an in vitro defect in the signal transduction pathway of the TcR/CD3 complex, resulting in ineffective PKC activation which is not able to induce normal IL-2 production and proliferation of diabetic T cells.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

In vivo administration of azithromycin affects lymphocyte activity in vitro

A therapeutic dose of azithromycin was administered to test subjects and then the following lymphocyte functions were examined in vitro: proliferative lymphocyte response to stimulation with pokeweed mitogen, levels of immunoglobulins G, A, and M in serum, and the amount of the soluble interleukin 2 receptors in supernatants of mononuclear cell cultures stimulated with phytohemagglutinin and phorbol myristate acetate. The study was performed as a controlled clinical trial comparing an azithromycin-treated group (n = 21) and a placebo-treated control group (n = 10). Healthy female volunteers were placed into one of the two groups, and the study was performed as a double-blind trial. Although the findings of the present study showed that azithromycin significantly increased the proliferative lymphocyte response to pokeweed mitogen, the results could have been due to experimental variation. However, impairment of the lymphocyte function was not observed, which could represent valuable information. Likewise, no effect of azithromycin on levels of the immunoglobulins in serum was observed. The most marked effect of azithromycin on the lymphocyte function was demonstrated by an elevation in the amount of soluble interleukin 2 receptor production in mononuclear cell cultures. The lack of impairment or, perhaps, even a beneficial influence on the immunodefense system may be an important property of azithromycin, especially in immunocompromised individuals.

Polygenic control of autoimmune diabetes in nonobese diabetic mice

Partial exclusion mapping of the nonobese (NOD) diabetic mouse genome has shown linkage of diabetes to at least five different chromosomes. We have now excluded almost all of the genome for the presence of susceptibility genes with fully recessive effects and have obtained evidence of linkage of ten distinct loci to diabetes or the prediabetic lesion, insulitis, indicative of a polygenic mode of inheritance. The relative importance of these loci and their interactions have been assessed using a new application of multiple polychotomous regression methods. A candidate disease gene, interleukin-2 (Il-2), which is closely linked to insulitis and diabetes, is shown to have a different sequence in NOD, including an insertion and a deletion of tandem repeat sequences which encode amino acid repeats in the mature protein.

Elevated serum soluble interleukin-2 receptor levels in subacute cutaneous lupus erythematosus

Subacute cutaneous lupus erythematosus (SCLE) is a subset of lupus erythematosus which is characterized by unique cutaneous manifestations and immunological abnormalities. Soluble IL-2 receptor (sIL-2 R) is the shed product of membrane Il-2 R, a product of T cell activation. It is measured by enzyme-linked immunosorbent assay (ELISA) and has been found to correlate well with disease activity in systemic lupus erythematosus (SLE) patients. The objective of the present work was to determine whether there is a correlation between sIL-2 R levels and disease activity in SCLE. Serum samples were obtained from 25 SCLE patients and then measured for sIL-2 R levels of ELISA. Fifteen of 25 SCLE patients tested had normal levels of sIL-2 R, while 10 of 25 SCLE patients had elevated sIL-2 R levels. The serum sIL-2 R level in SCLE patients correlated well with disease activity and the number of American College of Rheumatology criteria for SLE. These findings indicate that sIL-2 R levels can be used as a valuable laboratory parameter in managing SCLE patients.

Compartmentalization of the peripheral immune system

The periphery of the immune system--as opposed to the central lymphoid organs--contains inhomogeneously distributed B and T cells whose phenotype, repertoire, developmental origin, and function are highly divergent. Nonconventional lymphocytes bearing a phenotype that is rare in the blood, spleen, or lymph nodes of undiseased individuals are encountered at high frequency in different localizations, e.g., alpha/beta TCR+CD4-CD8- cells in the bone marrow and gut epithelium, particular invariant gamma/delta TCR+CD4-CD8 alpha+CD8 beta- and gamma/delta TCR+CD4-CD8 alpha-CD8 beta- T cells in various epithelia, or CD5+ B cells in the peritoneum. The antigen receptor repertoire is different in each localization. Thus, different gamma/delta TCR gene products dominant in each site, and the proportion of cells expressing transgenic and endogenous alpha/beta TCR and immunoglobulin gene products follows a gradient, with a maximum of endogenous gene expression in the peritoneum, intermediate values in other peripheral lymphoid organs (spleen, lymph nodes), and minimum values in thymus and bone marrow. Forbidden T cells that bear self-superantigen-reactive V beta gene products are physiologically detected among alpha/beta TCR+CD4-CD8- lymphocytes of the bone marrow, as well as in the gut. Violating previous ideas on self-tolerance preservation, self-peptide-specific gamma/delta T cells are present among intestinal intraepithelial lymphocytes, and CD5+ B cells produce low-affinity crossreactive autoantibodies in a physiological fashion. It appears that, in contrast to the bulk of T and B lymphocytes, certain gamma/delta and alpha/beta T cells found in the periphery, as well as most CD5+ B cells, do not depend on the thymus or bone marrow for their development, respectively, but arise from different, nonconventional lineages. In addition to divergent lineages that are targeted to different organs guided by a spatiotemporal sequence of tissue-specific homing receptors, local induction or selection processes may be important in the diversification of peripheral lymphocyte compartments. Selection may be exerted by local antigens, antigen-presenting cells whose function varies in each anatomical localization, cytokines, and cell-matrix interactions, thus leading to the expansion and maintenance of some clones, whereas others are diluted out or deleted. The spatial compartmentalization of lymphocytes in different microenvironments has major functional consequences and leads to a partial fragmentation of immunoregulatory circuits at the local level. Lymphocytes residing in certain antigen-exposed compartments are likely to combat tissue-specific pathogens or self-proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

gamma-Interferon, interleukin-4 and interleukin-6 in vitro production in old subjects

It is well known that ageing is associated with various alterations of the lymphoid cell functions. Although both B and T cell are affected, the last appear to be more sensitive to ageing process. During the past years, to gain insight into thé mechanism(s) of this impairment, effort has been centered on the helper T cells specifically engaged in the production of interleukin-2 (IL-2) because of the pivotal role played by this cytokine in the activation of several immune functions. The results have demonstrated that the ability to produce IL-2 declines with age. In this paper we report the results of a study performed to determine the influence of age on the capacity to produce gamma-interferon (gamma-IFN), interleukin-4 (IL-4) and interleukin-6 (IL-6). Mononuclear cells from young and old subjects were assessed for cytokine producing capacity in response to phytohaemagglutinin stimulation. A significant decrease of gamma-IFN production by old subjects has been observed. No significant difference was instead observed between the old subjects and the young ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in elderly, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.

Dissociation of autoaggression and self-superantigen reactivity

Self-superantigens have been described as products of endogenous retroviruses of the mouse ('minor lymphocyte stimulating loci') that are capable of interacting without prior processing with conserved domains of TCR V beta chains, causing the activation and deletion of most T cells expressing products of determined V beta gene families [1-4]. The fact that superantigens activate a far higher percentage of T cells (1-20%) than conventional, peptidic antigens (< 0.1%) provides the methodological advantage that the degree of clonal deletion may be measured by the analysis of the TCR repertoire using appropriate anti-V beta antibodies. Although much information on the spatio-temporal organization of repertoire-purging has been gathered by virtue of self-superantigens, serious doubts exist as to the possibility that such structures serve as pathogenetically relevant autoantigens. Thus, certain inbred mice spontaneously develop autoimmune diseases, although they bear T-cell repertoires that appear to be purged from self-superantigen-reactive V beta products. In addition, therapeutic interventions targeted to V beta gene products that are not specific for self-superantigens are successful in preventing disease development. The lack of correlation between superantigen-related V beta deletions and autoimmune disease development is substantiated in further models of murine autoimmunity. Based on these observations, we formulate the hypothesis that self-superantigen-reactive T cells are not involved in the development of autoimmune diseases.

Possible role for cytotoxic lymphocytes in the pathogenesis of acute interstitial nephritis after recombinant interleukin-2 treatment for renal cell cancer

A patient with renal cell cancer developed acute renal failure due to biopsy-proven acute tubulo-interstitial nephritis (AIN) in the 6th week of continuous infusion of 9 x 10(6) IU m-2 day-1 recombinant interleukin-2 (rIL-2). We investigated whether the AIN was the result of a cellular cytotoxic reaction induced by the rIL-2 treatment. The cytolytic activity of cryopreserved peripheral blood lymphocytes (PBL), isolated before and at the end of the rIL-2 treatment (at the time of AIN), was studied after 5 days of culture with or without rIL-2 or anti-CD28 and immobilized anti-CD3 antibodies. The PBL isolated before and at the end of the rIL-2 treatment showed cytolytic activity towards a number of allogeneic targets. However, only the PBL isolated at the end of the rIL-2 treatment showed, when stimulated with rIL-2 in vitro, significant cytolytic activity against an autologous renal cell line cultured from the AIN biopsy specimen and against an allogeneic renal cell cancer cell line. These PBL displayed no enhanced killing capacity towards autologous PBL and the melanoma cell line M14. These observations suggest that the AIN may be the result of a cytotoxic lymphocyte-mediated reaction induced by the rIL-2 treatment.