Interleukin 16: implications for CD4 functions and HIV-1 progression

Involvement of CD4+ and CD8+ T-lymphocytes in the modulation of nociceptive processing evoked by CCL4 in mice

AIMS

To explore the mechanisms involved in the transformation of analgesia produced by low doses of CCL4 (pg/kg) to hyperalgesia when higher doses (ng/kg) are administered to mice.

MAIN METHODS

The unilateral hot plate test was used to assess thermal nociception. CD3⁺, CD4⁺ or CD8⁺ blood cells were depleted with selective antibodies. Expression of CCR5 and IL-16 in lymphocytes was studied by flow cytometry and IL-16 blood levels were measured by ELISA. IL-16 and CD8 were detected by immunofluorescence.

KEY FINDINGS

IL-16 and CCR5 expression were demonstrated in CD4⁺ and CD8⁺ T-lymphocytes by flow cytometry. Furthermore, CCL4-induced hyperalgesia was abolished by reducing circulating T-lymphocyte levels or by selectively depleting CD4⁺ lymphocytes. In contrast, when the anti-CD4 antibody was acutely administered, CCL4 induced analgesia instead of hyperalgesia. A similar response was obtained when administering A-770041, that prevents CD4-mediated CCR5 desensitization by inhibiting p56^lck kinase. As occurred with the analgesic effect evoked by low doses of CCL4, analgesia evoked by combining CCL4 and A-770041 was reverted by naloxone, naltrindole or an anti-met-enk antibody. Interestingly, flow cytometry assays showed that the number of CD8⁺, but not CD4⁺, T-cells expressing IL-16 is reduced after the acute administration of CCL4, a result compatible with the description that CD8⁺-lymphocytes can rapidly release preformed IL-16. Accordingly, the rise in IL-16 blood concentration evoked by CCL4 was prevented after CD8⁺ lymphocyte depletion.

SIGNIFICANCE

CCL4-evoked hyperalgesia is related to the desensitization of CCR5 in CD4⁺ T-cells and to the release of IL-16 from CD8⁺ lymphocytes.

Association of IL16 polymorphisms with periodontitis in Brazilians: A case- control study

Periodontitis (PD) is a chronic inflammatory process resulting from the relationship of the immune response with the components in dental plaque. Cytokines and their genetic polymorphisms seem to be involved in the immunopathogenesis of this disease. This study aimed to evaluate the correlation of IL16 polymorphism with PD. A case-control study was conducted in a sample of individuals from southern Brazil. The genotyping of IL16, rs11556218 T>G, rs4072111 C>T e rs4778889 T>C, was performed using the PCR-RFLP methodology. The serum level of IL-16 was determined using an IL-16 ELISA kit for humans. SNPStats and OpenEpi software and Wilcoxon's U test were used to perform statistical analysis. IL16 rs11556218 polymorphism was significantly associated to PD in nonsmoking patients: individuals with G/G genotype were less likely to develop PD compared to the T/T genotype (OR = 0.10; Pc = 0.019, codominant model). In addition, the TTT haplotype was associated with a high risk for PD (OR = 2.45; P = 0.01). A low IL-16 serum level was observed among individuals with PD when compared to controls (P = 0.027). Thus, the IL16 rs16556218 polymorphism and the serum levels of IL-16 were associated with periodontitis in a Brazilian sample, and this was influenced by environmental factors such as smoking.

Association of functional IL16 polymorphisms with cancer and cardiovascular disease: a meta-analysis

INTRODUCTION

Interleukin-16 (IL-16) is a chemotactic cytokine that is found to increase in Cancer and cardiovascular diseases (CVD). Single nucleotide polymorphisms (SNPs) in IL16 were associated with diseases. Thus, we conducted a systematic review and meta-analysis to evaluate possible associations between IL16 rs4778889, rs11556218, rs4072111, and rs1131445 SNPs and the risk for cancer or CVD.

MATERIALS AND METHODS

This study was performed according to the PRISMA statement. Medline, Web of Science, and Scopus databases were systematically reviewed, and a meta-analysis was conducted.

RESULTS

The analysis comprised 6386 individuals with cancer and 2415 with CVD. The SNP rs11556218 was significantly associated with an increased risk for cancer in Chinese in different genetic inheritance models. Also, to the best of our knowledge, this is the first meta-analysis to show an association of rs4778889 with an increased risk of gastric cancer and rs11556218 with an increased risk of CVD in Chinese.

CONCLUSIONS

Our meta-analysis suggested that the SNPs rs11556218 and rs4778889 of IL16 were associated with an increased risk for cancer in Chinese and rs11556218 with increased risk for CVD in Chinese, highlighting the need for further studies on the impact of these polymorphisms on cancer treatment and surveillance.

Diagnostic Potential of Novel Salivary Host Biomarkers as Candidates for the Immunological Diagnosis of Tuberculosis Disease and Monitoring of Tuberculosis Treatment Response

Background

There is an urgent need for new tools for the early diagnosis of TB disease and monitoring of the response to treatment, especially in resource-constrained settings. We investigated the usefulness of host markers detected in saliva as candidate biomarkers for the immunological diagnosis of TB disease and monitoring of treatment response.

Methods

We prospectively collected saliva samples from 51 individuals that presented with signs and symptoms suggestive of TB disease at a health centre in Cape Town, South Africa, prior to the establishment of a clinical diagnosis. Patients were later classified as having TB disease or other respiratory disease (ORD), using a combination of clinical, radiological and laboratory findings. We evaluated the concentrations of 69 host markers in saliva samples using a multiplex cytokine platform, and assessed the diagnostic potentials of these markers by receiver operator characteristics (ROC) curve analysis, and general discriminant analysis.

Results

Out of the 51 study participants, 18 (35.4%) were diagnosed with TB disease and 12 (23.5%) were HIV infected. Only two of the 69 host markers that were evaluated (IL-16 and IL-23) diagnosed TB disease individually with area under the ROC curve ≥0.70. A five-marker biosignature comprising of IL-1β, IL-23, ECM-1, HCC1 and fibrinogen diagnosed TB disease with a sensitivity of 88.9% (95% CI,76.7–99.9%) and specificity of 89.7% (95% CI, 60.4–96.6%) after leave-one-out cross validation, regardless of HIV infection status. Eight-marker biosignatures performed with a sensitivity of 100% (95% CI, 83.2–100%) and specificity of 95% (95% CI, 68.1–99.9%) in the absence of HIV infection. Furthermore, the concentrations of 11 of the markers changed during treatment, indicating that they may be useful in monitoring of TB treatment response.

Conclusion

We have identified novel salivary biosignatures which may be useful in the diagnosis of TB disease and monitoring of the response to TB treatment. Our findings require further validation in larger studies before these biosignatures could be considered for point-of-care screening test development.

Allo-antigen stimulated CD8+ T-cells suppress NF-κB and Ets-1 DNA binding activity, and inhibit phosphorylated NF-κB p65 nuclear localization in CD4+ T-cells

CD8+ T-cells of asymptomatic HIV-1 carriers (AC) suppress human immunodeficiency virus type 1 (HIV-1) replication in a class I major histocompatibility complex (MHC-I)-restricted and -unrestricted manner. In order to investigate the mechanism of MHC-I-unrestricted CD8+ T-cell-mediated HIV-1 suppression, we previously established allo-antigen stimulated CD8+T-cells from HIV-1-uninfected donors. These allo-antigen stimulated CD8+ T-cells suppressed HIV-1 replication in acutely infected autologous CD4+ T-cells when directly co-cultured. To elucidate the mechanism of HIV-1 replication suppression, we analyzed DNA-binding activity and phosphorylation of transcriptional factors associated with HIV-1 replication by electrophoresis mobility shift assay and Western blotting. When CD4+ T-cells were cultured with allo-antigen stimulated CD8+ T-cells, the reduction of NF-κB and Ets-1 DNA-binding activity was observed. Nuclear localization of NF-κB p65 and Ets-1 was suppressed in CD4+ T-cells. Although NF-κB p65 and Ets-1 are known to be regulated by protein kinase A (PKA), no difference was observed in the expression and phosphorylation of the PKA catalytic subunit in CD4+ T-cells cultured with PHA-treated CD8+ T-cells or allo-antigen stimulated CD8+ T-cells. Cyclic AMP is also known to enter through gap junctions, but the suppression of HIV-1 replication mediated by allo-antigen stimulated CD8+ T-cells was not affected by the gap junction inhibitor. The nuclear transport of phosphorylated NF-κB p65 (Ser276) was inhibited only in CD4+ T-cells cultured with allo-antigen stimulated CD8+ T-cells. Our results indicate that allo-antigen stimulated CD8+ T-cells suppress the transcriptional activity of NF-κB p65 or Ets-1 in an antigen-nonspecific manner, and inhibit the nuclear transport of phosphorylated NF-κB p65 (Ser276).

Changes in serum cytokines in response to musculoskeletal surgical trauma

Background

Trauma induces local and subsequent systemic inflammatory reactions, and when the cytokine production is deregulated, a systemic inflammatory response syndrome with a potentially lethal outcome can occur. The understanding of the physiological mechanism of the cytokine network would be useful to better comprehend pathological conditions.

Methods

We analysed a panel of 30 cytokines in the serum of 20 patients operated with total hip replacement. Cytokine release was assessed postoperatively up to 6 days by a multiplex antibody bead kit and compared to pre-operative values.

Results

Surgery induced significant increments in serum levels of IL-2R at 6 days after surgery, in levels of IL-6 at 6 hours after surgery and at 1 day after surgery, in levels of IL-8 at 6 hours after surgery, in levels of IL-16 at 6 hours and at 1 day after surgery. Significant decreases in serum levels of IL-1Rα were found at the end of surgery, in levels of IL-12 at the end of surgery and at 6 hours after, and in levels of Eotaxin during all phases of the postoperative course.

Conclusions

The major findings were significant increases in systemic levels of the pro-inflammatory cytokines IL-6, IL-8, IL-16, while IL-12 was significantly decreased. Otherwise there were modest changes in the systemic cytokine kinetics and no significant expression of anti-inflammatory cytokines.

The leech nervous system: a valuable model to study the microglia involvement in regenerative processes

Microglia are intrinsic components of the central nervous system (CNS). During pathologies in mammals, inflammatory processes implicate the resident microglia and the infiltration of blood cells including macrophages. Functions of microglia appear to be complex as they exhibit both neuroprotective and neurotoxic effects during neuropathological conditions in vivo and in vitro. The medicinal leech Hirudo medicinalis is a well-known model in neurobiology due to its ability to naturally repair its CNS following injury. Considering the low infiltration of blood cells in this process, the leech CNS is studied to specify the activation mechanisms of only resident microglial cells. The microglia recruitment is known to be essential for the usual sprouting of injured axons and does not require any other glial cells. The present review will describe the questions which are addressed to understand the nerve repair. They will discuss the implication of leech factors in the microglial accumulation, the identification of nerve cells producing these molecules, and the study of different microglial subsets. Those questions aim to better understand the mechanisms of microglial cell recruitment and their crosstalk with damaged neurons. The study of this dialog is necessary to elucidate the balance of the inflammation leading to the leech CNS repair.

A homologous form of human interleukin 16 is implicated in microglia recruitment following nervous system injury in leech Hirudo medicinalis

In contrast to mammals, the medicinal leech Hirudo medicinalis can completely repair its central nervous system (CNS) after injury. This invertebrate model offers unique opportunities to study the molecular and cellular basis of the CNS repair processes. When the leech CNS is injured, microglial cells migrate and accumulate at the site of lesion, a phenomenon known to be essential for the usual sprouting of injured axons. In the present study, we demonstrate that a new molecule, designated HmIL-16, having functional homologies with human interleukin-16 (IL-16), has chemotactic activity on leech microglial cells as observed using a gradient of human IL-16. Preincubation of microglial cells either with an anti-human IL-16 antibody or with anti-HmIL-16 antibody significantly reduced microglia migration induced by leech-conditioned medium. Functional homology was demonstrated further by the ability of HmIL-16 to promote human CD4+ T cell migration which was inhibited by antibody against human IL-16, an IL-16 antagonist peptide or soluble CD4. Immunohistochemistry of leech CNS indicates that HmIL-16 protein present in the neurons is rapidly transported and stored along the axonal processes to promote the recruitment of microglial cells to the injured axons. To our knowledge, this is the first identification of a functional interleukin-16 homologue in invertebrate CNS. The ability of HmIL-16 to recruit microglial cells to sites of CNS injury suggests a role for HmIL-16 in the crosstalk between neurons and microglia in the leech CNS repair.

The myosin phosphatase targeting protein (MYPT) family: a regulated mechanism for achieving substrate specificity of the catalytic subunit of protein phosphatase type 1δ

The mammalian MYPT family consists of the products of five genes, denoted MYPT1, MYPT2, MBS85, MYPT3 and TIMAP, which function as targeting and regulatory subunits to confer substrate specificity and subcellular localization on the catalytic subunit of type 1δ protein serine/threonine phosphatase (PP1cδ). Family members share several conserved domains, including an RVxF motif for PP1c binding and several ankyrin repeats that mediate protein-protein interactions. MYPT1, MYPT2 and MBS85 contain C-terminal leucine zipper domains involved in dimerization and protein-protein interaction, whereas MYPT3 and TIMAP are targeted to membranes via a C-terminal prenylation site. All family members are regulated by phosphorylation at multiple sites by various protein kinases; for example, Rho-associated kinase phosphorylates MYPT1, MYPT2 and MBS85, resulting in inhibition of phosphatase activity and Ca(2+) sensitization of smooth muscle contraction. A great deal is known about MYPT1, the myosin targeting subunit of myosin light chain phosphatase, in terms of its role in the regulation of smooth muscle contraction and, to a lesser extent, non-muscle motile processes. MYPT2 appears to be the key myosin targeting subunit of myosin light chain phosphatase in cardiac and skeletal muscles. MBS85 most closely resembles MYPT2, but little is known about its physiological function. Little is also known about the physiological role of MYPT3, although it is likely to target myosin light chain phosphatase to membranes and thereby achieve specificity for substrates involved in regulation of the actin cytoskeleton. MYPT3 is regulated by phosphorylation by cAMP-dependent protein kinase. TIMAP appears to target PP1cδ to the plasma membrane of endothelial cells where it serves to dephosphorylate proteins involved in regulation of the actin cytoskeleton and thereby control endothelial barrier function. With such a wide range of regulatory targets, MYPT family members have been implicated in diverse pathological events, including hypertension, Parkinson's disease and cancer.

Intranasal vasopressin affects pair bonding and peripheral gene expression in male Callicebus cupreus

Arginine vasopressin (AVP) is a neuropeptide hormone and neurotransmitter that has peripheral functions in water regulation, and central functions in the stress response and social bonding in male rodents. In this study, we investigated the role of AVP in partner preference behavior in a monogamous primate, the coppery titi monkey (Callicebus cupreus). Seven titi males each received three intranasal treatments: saline, low AVP (40 IU) and high AVP (80 IU) in random order, 1 week apart. They experienced a series of stimulus exposures to their female partner, a female stranger and an empty cage. Males were more likely to contact the stimulus and do so faster when either female stimulus was present. When pretreated with saline, males contacted the stranger more frequently than their partner; when pretreated with the high dosage of AVP, males contacted their partner more frequently than the stranger. We used microarray to measure peripheral changes in gene expression associated with intranasal AVP and found reduced expression of several genes coding for proinflammatory cytokines. The data presented here suggest that intranasally administered AVP has both central influences on social behavior and peripheral influences on inflammation in a nonhuman primate.

Low postseroconversion CD4 count and rapid decrease of CD4 density identify HIV+ fast progressors

CD4 expression in HIV replication is paradoxical: HIV entry requires high cell-surface CD4 densities, but replication requires CD4 down-modulation. However, is CD4 density in HIV+ patients affected over time? Do changes in CD4 density correlate with disease progression? Here, we examined the role of CD4 density for HIV disease progression by longitudinally quantifying CD4 densities on CD4+ T cells and monocytes of ART-naive HIV+ patients with different disease progression rates. This was a retrospective study. We defined three groups of HIV+ patients by their rate of CD4+ T cell loss, calculated by the time between infection and reaching a CD4 level of 200 cells/microl: fast (<7.5 years), intermediate (7.5-12 years), and slow progressors (>12 years). Mathematical modeling permitted us to determine the maximum CD4+ T cell count after HIV seroconversion (defined as "postseroconversion CD4 count") and longitudinal profiles of CD4 count and density. CD4 densities were quantified on CD4+ T cells and monocytes from these patients and from healthy individuals by flow cytometry. Fast progressors had significantly lower postseroconversion CD4 counts than other progressors. CD4 density on T cells was lower in HIV+ patients than in healthy individuals and decreased more rapidly in fast than in slow progressors. Antiretroviral therapy (ART) did not normalize CD4 density. Thus, postseroconversion CD4 counts define individual HIV disease progression rates that may help to identify patients who might benefit most from early ART. Early discrimination of slow and fast progressors suggests that critical events during primary infection define long-term outcome. A more rapid CD4 density decrease in fast progressors might contribute to progressive functional impairments of the immune response in advanced HIV infection. The lack of an effect of ART on CD4 density implies a persistent dysfunctional immune response by uncontrolled HIV infection.

Differential microglial regulation in the human spinal cord under normal and pathological conditions

As the primary intrinsic immune effector cells of the central nervous system, microglia are involved in virtually all pathological processes of the brain and spinal cord including inflammatory, neurodegenerative, traumatic, neoplastic and vascular diseases. Despite this important role, there is a lack of data concerning microglial distribution and protein expression in the human spinal cord. In this study, we immunohistochemically investigated 10 normal human spinal cords to establish reference data and compared these results with 15 pathological human spinal cords deriving from distinct pathologies. Each spinal cord was evaluated at eight different levels for three white and two grey matter areas for both constitutive (MHC-II, CD68, IL-16, AIF-1, LCA, CD4) and reactive (MRP-8, MRP-14) microglial antigens. Whereas previous studies revealed significant regional differences in microglial distribution and protein expression in human brain, normal spinal cord displayed a uniform expression pattern, reaching levels of up to 17% MHC-II positive cells of the total cell population. This datum formed the basis for the further evaluation of microglia expression levels in pathological spinal cords, where levels of up to 45% positive cells were observed. Our results represent important reference values for future neuropathological diagnostic and therapeutical approaches in spinal cord pathologies.

Not-so-sweet sixteen: the role of IL-16 in infectious and immune-mediated inflammatory diseases

Over the past two decades, our understanding of interleukin-16 (IL-16) has increased substantially. Initial studies characterizing IL-16 as a chemotactic cytokine (but not a chemokine) just scratched the surface of the unique properties of this cytokine. Since then, scientists have determined that IL-16 has a wide range of effects on cells, including upregulation of CD25, induction of cells to progress to the G(1) phase, inhibition of antigen- specific proliferation yet with retained antigen nonspecific proliferative properties, and discovery of a novel neuronal form with unique properties. Recently, a plethora of studies have implicated IL-16 in exacerbation of infectious, immune-mediated, and autoimmune inflammatory disorders, including atopic dermatitis, irritable bowel syndrome, systemic lupus erythematosus, neurodegenerative disorders, and viral infections. Herein, we review the body of evidence supporting a role for IL-16 in infectious and immune-mediated inflammatory disorders and explore the known and possible mechanism of actions in the numerous diseases.

Spinal cord injury-induced expression of the immune-regulatory chemokine interleukin-16 caused by activated microglia/macrophages and CD8+ cells

OBJECT

Spinal cord injury (SCI) elicits a strong inflammatory response that readily participates in lipid oxygenation, edema formation, apoptotic cell death, and tissue remodeling. Because cytokines determine the postinjury inflammatory milieu, the authors analyzed the expression of the immunomodulatory chemokine interleukin- 16 (IL- 16) after SCI.

METHODS

The authors detected a highly significant, persistent, lesional accumulation of parenchymal IL-16+ microglia/macrophages, which reached a maximal level 3 days postinjury compared with control rats. The majority of cells that demonstrated positive labeling for IL-16 also had positive labeling for ED1 (> 70%) and OX-8/CD8; these cells exhibited the morphological hallmarks of activated microglia/macrophages and pronounced MHC Class II expression. In contrast to IL-16+ED1+ cells, IL-16+ microglia/macrophages that coexpressed OX-8 were exclusively seen in the pannecrotic lesion core. In addition, clustering of IL-16+ cells was observed in perivascular Virchow-Robin-like spaces in areas of the primary injury (lesion core) and in immediately adjacent areas of secondary injury. Furthermore, on Day 3 postinjury, IL-16+ microglia/macrophages were frequently observed in a perineuronal position.

CONCLUSIONS

The early lesional accumulation of IL-16+ microglia/macrophages suggests a role for IL-16 in the early postinjury immune response such as recruitment and activation of immune cells, leading to microvessel clustering and secondary damage progression.

Alterations in mesenteric lymph node T cell phenotype and cytokine secretion are associated with changes in thymocyte phenotype after LP-BM5 retrovirus infection

In this study, mouse MLN cells and thymocytes from advanced stages of LP-BM5 retrovirus infection were studied. A decrease in the percentage of IL-7(+) cells and an increase in the percentage of IL-16(+) cells in the MLN indicated that secretion of these cytokines was also altered after LP-BM5 infection. The percentage of MLN T cells expressing IL-7 receptors was significantly reduced, while the percentage of MLN T cells expressing TNFR-p75 and of B cells expressing TNFR-p55 increased. Simultaneous analysis of surface markers and cytokine secretion was done in an attempt to understand whether the deregulation of IFN-gamma secretion could be ascribed to a defined cell phenotype, concluding that all T cell subsets studied increased IFN-gamma secretion after retrovirus infection. Finally, thymocyte phenotype was further analyzed trying to correlate changes in thymocyte phenotype with MLN cell phenotype. The results indicated that the increase in single positive either CD4(+)CD8(-) or CD4(-)CD8(+) cells was due to accumulation of both immature (CD3(-)) and mature (CD3(+)) single positive thymocytes. Moreover, single positive mature thymocytes presented a phenotype similar to the phenotype previously seen on MLN T cells. In summary, we can conclude that LP-BM5 uses the immune system to reach the thymus where it interferes with the generation of functionally mature T cells, favoring the development of T cells with an abnormal phenotype. These new T cells are activated to secrete several cytokines that in turn will favor retrovirus replication and inhibit any attempt of the immune system to control infection.

The immunocompromised host: HIV infection

The variety of pulmonary infections encountered in HIV-infected individuals indicates that many components of the host defense network are impaired. In addition to depletion of CD4+ T cell numbers, HIV infection results in functional deficits in CD4+ T cells, CD8+ T cells, and natural killer cells. Although some components of macrophage defense are preserved, lack of activation signals from CD4+ T cells contributes to impaired defense by macrophages. There are few data examining the functional capabilities of neutrophils in the lung, but evidence from peripheral blood neutrophils indicates that defense by these cells is also impaired. An improved understanding of these events in the lung during HIV infection could lead to specific interventions aimed at restoration of deficient function.

Interleukin-16 inhibits interleukin-13 production by allergen-stimulated blood mononuclear cells

Expression of interleukin (IL)-16 is increased in bronchial mucosal biopsies of atopic asthmatics compared to normal controls. The functional significance of increased expression of IL-16 at sites of allergic inflammation is not yet clear. We have previously shown that IL-16 inhibits IL-5 secretion by allergen-stimulated peripheral blood mononuclear cells (PBMC). We investigated whether IL-16 inhibits the production of other T helper 2 cytokines, namely IL-13 and IL-4, by allergen-specific T cells. PBMC from ragweed-sensitive atopic subjects were stimulated with allergen extract for cytokine production in the presence or absence of rhIL-16. Production of cytokines was assessed by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction. To evaluate whether the modulatory effect of IL-16 on cytokine synthesis was mediated by interferon-gamma (IFN-gamma), IL-10, IL-12 or IL-18, allergen-stimulated PBMC were cultured in presence of IL-16 and neutralizing concentrations of relevant antibodies. Allergen-stimulated PBMC produced significantly elevated levels of IL-13 (90-740 pg/ml) as compared to unstimulated PBMC (0-375 pg/ml, P < 0.01). Addition of rhIL-16 resulted in down-regulation of IL-13 mRNA expression as well as significantly reduced amounts of IL-13 released by allergen-stimulated PBMC (0-457 pg/ml, P < 0.001), as observed for IL-5. No effect of IL-16 was observed on IL-4 mRNA expression. Treatment with IL-16 resulted in increased levels of IL-10 and IL-18 in allergen-stimulated cell culture. Neutralization of IFN-gamma, IL-12, IL-10 or IL-18 did not alter the inhibitory effects of IL-16 on IL-13 and IL-5 secretion by allergen-stimulated PBMC. IL-16 did not modify IL-13 synthesis by anti-CD3-stimulated CD4(+) T cells, but it significantly reduced the production of IL-5. These data suggest that IL-16 may play an important immunoregulatory role in allergic states in response to allergen.

Interleukin-16 expression in the peripheral blood and CD8 T lymphocytes after traumatic injury

BACKGROUND

Expressed in several pathologic conditions, interleukin (IL-16) can induce chemotaxis and regulate the activation of CD4-positive leukocytes. This study investigated the expression of IL-16 in trauma patient plasma and peripheral blood leukocytes to determine its involvement in the physiologic response to injury.

METHODS

In this study, 25 consecutive patients requiring trauma team activation and 15 noninjured subjects were evaluated for plasma IL-16 by enzyme-linked immunosorbent assay and peripheral blood leukocyte expression of intracellular cytokine by flow cytometry.

RESULTS

Trauma patient plasma IL-16 was transiently increased after injury in comparison with levels in noninjured control subjects. In patients with worse outcome, both peripheral blood T lymphocyte intracellular IL-16 levels and CD4/CD8 lymphocyte ratios were lower than those for less severely injured patients and control subjects.

CONCLUSION

Posttraumatic changes in IL-16 expression were found to be associated with worse patient outcome, suggesting an innate immune mechanism with a role in regulation of the T lymphocyte response to injury.

The CD4 molecule on CD8+ T lymphocytes directly enhances the immune response to viral and cellular antigens

CD8+ T lymphocytes play a major role in cellular-mediated immune responses to foreign antigen. We have previously demonstrated that costimulation of purified human CD8+ T cells induces de novo expression of the CD4 molecule and that ligation of CD4 on this cell type modulates CD8+ T cell activity in vitro. Herein, we investigate how the CD4 molecule expressed on murine CD8+ T cells contributes to CD8+ cell responses in vivo by employing adoptive transfer of CD8 cells from CD4 knockout mice into severe combined immunodeficient (SCID) recipients. Transfer of these cells into syngeneic SCID mice resulted in a decreased immune response to infection by lymphocytic choriomeningitis virus. These decreased responses occurred even in the presence of CD4+ T cells, indicating that this was truly a CD8-cell defect. Similarly, transfer of CD8+ T cells incapable of expressing CD4 into allogeneic SCID mice resulted in a decreased response to alloantigens compared with that of normal CD8+ T cells. Therefore, CD4 expression on CD8 T lymphocytes modulates cytotoxic T lymphocyte function and is critical in vivo for optimal cell-mediated immunity to viral and alloantigens.

IL-16 activates plasminogen-plasmin system and promotes human eosinophil migration into extracellular matrix via CCR3-chemokine-mediated signaling and by modulating CD4 eosinophil expression

Increased eosinophil counts are a major feature of asthmatic airways. Eosinophil recruitment requires migration through epithelium and tissue extracellular matrix by activation of proteases. We assessed the capacity of IL-16, a CD4(+) cell chemotactic factor, to induce migration of eosinophils through a reconstituted basement membrane and evaluated the proteases, mediators, and receptors involved in this migration. IL-16 added to lower chambers of Invasion Chambers elicited eosinophil migration through Matrigel. This effect was decreased by inhibition of the plasminogen-plasmin system (Abs against urokinase plasminogen activator receptor or plasminogen depletion), but not by anti-matrix metalloproteinase-9 Abs. Abs against CD4 also inhibited IL-16-induced eosinophil migration. At the baseline level, few eosinophils (4.6% positive cells with a mean fluorescence of 0.9) expressed surface membrane CD4, while most permeabilized eosinophils (68% positive cells with a mean fluorescence of 18) express the CD4 Ag. TNF-pretreatment increased surface membrane CD4(+) expression by 6-fold as previously described, and increased IL-16-induced cell migration by 2.2-fold. Incubation of eosinophils with IL-16 also increased surface membrane CD4 expression by 5.4-fold, supporting the role of CD4 as receptor for IL-16. Abs against CCR3, eotaxin, or RANTES blocked IL-16-induced migration. In conclusion, IL-16 promotes eosinophil migration in vitro, by activating the plasminogen-plasmin system and increasing the membrane expression of its receptor. This effect is initiated via CD4 and mediated via the release of CCR3 ligand chemokines. Interestingly, most eosinophils express intracellular CD4. Hence, IL-16 may play an important role in the recruitment of blood eosinophils to the bronchial mucosa of asthmatics.

Interleukin-16 expression and release in bullous pemphigoid

Cutaneous infiltration of activated CD4(+) T cells and eosinophils is an early event in blister formation during bullous pemphigoid (BP), suggesting that the trafficking of circulating leucocytes through the sites of inflammation, their activation and cytokine release is crucial in the pathogenesis of the disease. IL-16 is a major chemotactic factor able to recruit CD4(+) cells in the skin during inflammation and to induce the expression of functional high-affinity interleukin (IL)-2 receptors, thus contributing to cellular activation and proliferation. We performed a study in order to evaluate the presence of IL-16 in skin samples and sera and blister fluids of patients affected with BP in active phase of the disease (n = 39), compared with healthy donors studied as control group. Ten patients were also evaluated before and after steroid therapy. Our results demonstrated that IL-16 was expressed strongly by keratinocytes and by dermal infiltrating CD4(+) T lymphocytes in lesional skin of BP patients. High levels of IL-16 were detected in sera and blisters of BP, significantly higher in respect to healthy donors. When patients were investigated for the presence of eosinophil cationic protein (ECP) and soluble CD30 (sCD30) to reveal signs of eosinophils and Th2-cells activation, we found a positive correlation between IL-16 serum levels and both ECP and sCD30, suggesting that IL-16 is involved in Th2 lymphocytes and eosinophils recruitment during BP.

CD4 on CD8(+) T cells directly enhances effector function and is a target for HIV infection

Costimulation of purified CD8(+) T lymphocytes induces de novo expression of CD4, suggesting a previously unrecognized function for this molecule in the immune response. Here, we report that the CD4 molecule plays a direct role in CD8(+) T cell function by modulating expression of IFN-gamma and Fas ligand, two important CD8(+) T cell effector molecules. CD4 expression also allows infection of CD8 cells by HIV, which results in down-regulation of the CD4 molecule and impairs the induction of IFN-gamma, Fas ligand, and the cytotoxic responses of activated CD8(+) T cells. Thus, the CD4 molecule plays a direct role in CD8 T cell function, and infection of these cells by HIV provides an additional reservoir for the virus and also may contribute to the immunodeficiency seen in HIV disease.

PDZ Domain-mediated interaction of interleukin-16 precursor proteins with myosin phosphatase targeting subunits

The cytokine interleukin-16 is generated by posttranscriptional cleavage by caspase-3 of two large precursor isoforms. The smaller protein of 67 kDa (pro-IL-16) is expressed in cells of the immune system and contains three PDZ (postsynaptic density/disc large/zona occludens-1) domains, whereas the larger 141-kDa neuronal variant (npro-IL-16) has two additional PDZ domains in its N-terminal extension that interact with neuronal ion channels. Using the yeast two-hybrid approach we have identified three closely related myosin phosphatase targeting subunits, MYPT1, MYPT2, and MBS85, as binding partners of the IL-16 precursor proteins. These interactions were verified using pull-down assays, coimmunoprecipitations, and plasmon resonance experiments. Binding requires the intact PDZ2 domain of pro-IL-16 and highly related C-terminal regions in the ligands consisting of a short leucine zipper and an indispensable serine at the -1 position, suggesting a novel unconventional PDZ binding mode. Pro-IL-16 and the myosin phosphatase targeting subunits colocalize along actomyosin filaments and stress fibers in transfected COS-7 cells. By modulating and targeting the catalytic phosphatase subunit to its substrates, MYPT1, MYPT2, and MBS85 regulate various contractile processes in muscle and non-muscle cells. Our findings indicate an involvement of the IL-16 precursor molecules in myosin-based contractile processes, most likely in cell motility, providing a functional link to the chemotactic activity of the mature cytokine. Alternatively, an intracellular complex of npro-IL-16, ion channels, and components of myosin motors in neurons suggests a role in protein targeting.

Suppression of HIV-1 Replication by HIV-1-Irrelevant CD8+Cytotoxic T Lymphocytes Resulting in Preservation of Persistently HIV-1-Infected CellsIn Vitro

CD8+ cells of asymptomatic HIV-1 carriers (AC) contain HIV-1-specific cytotoxic T lymphocytes (CTLs) but suppress HIV-1 replication in a class I major histocompatibility complex (MHC-I)-unrestricted manner. In order to selectively investigate the HIV-1-suppressive function of CTLs apart from HIV-1-specific cytotoxicity, HIV-1-irrelevant allo-specific CTLs were established from an HIV-1-uninfected individual and their HIV-1-suppressive activity against autologous CD4+ peripheral blood mononuclear cells (PBMC) was examined. We found that these CTLs significantly suppressed both R5 and X4-HIV-1 replication in either acutely or persistently infected autologous PBMC. Although these CTLs partially killed HIV-1-infected PBMC through Fas ligand, CTLs still suppressed late steps of HIV-1 replication in the presence of neutralizing antibodies to Fas ligand. HIV-1 replication in PBMC that had been suppressed by CTLs was reversible following depletion of CTLs from culture, analogous to the previous observation for CD8+ cell-depleted PBMC of AC. Induction of HIV-1 replication by CTL-depletion was amplified by addition of newly prepared CD4+ cells or activation with staphylococcal enterotoxin B. Our results indicate that CTLs can suppress HIV-1 replication in PBMC in an antigen-nonspecific manner and preserve infected cells in a state capable of restarting HIV-1 replication and transmission.

CD4+ NKT cells, but not conventional CD4+ T cells, are required to generate efferent CD8+ T regulatory cells following antigen inoculation in an immune-privileged site

Following inoculation of Ag into the anterior chamber (a.c.), systemic tolerance develops that is mediated in part by Ag-specific efferent CD8(+) T regulatory (Tr) cells. This model of tolerance is called a.c.-associated immune deviation. The generation of the efferent CD8(+) Tr cell in a.c.-associated immune deviation is dependent on IL-10-producing, CD1d-restricted, invariant Valpha14(+) NKT (iNKT) cells. The iNKT cell subpopulations are either CD4(+) or CD4(-)CD8(-) double negative. This report identifies the subpopulation of iNKT cells that is important for induction of the efferent Tr cell. Because MHC class II(-/-) (class II(-/-)) mice generate efferent Tr cells following a.c. inoculation, we conclude that conventional CD4(+) T cells are not needed for the development of efferent CD8(+) T cells. Furthermore, Ab depletion of CD4(+) cells in both wild-type mice (remove both conventional and CD4(+) NKT cells) and class II(-/-) mice (remove CD4(+) NKT cells) abrogated the generation of Tr cells. We conclude that CD4(+) NKT cells, but not the class II molecule or conventional CD4(+) T cells, are required for generation of efferent CD8(+) Tr cells following Ag introduction into the eye. Understanding the mechanisms that lead to the generation of efferent CD8(+) Tr cells may lead to novel immunotherapy for immune inflammatory diseases.

Inhibition of HIV-1 replication by the combined action of anti-gp41 single chain antibody and IL-16

HIV-1 replication is inhibited in T cells transfected with an anti-gp41 single chain antibody (ScFv) or IL-16. These two molecules target totally different events in the HIV-1 replication cycle. The present study shows that HIV-1 replication is inhibited to a substantially greater extent and for a longer duration in cells transfected with both anti-gp41 and IL-16 than with either molecule alone. It is concluded that anti-gp41 and IL-16 act in a synergistic fashion to inhibit HIV-1 replication.

Circulating interleukin 16 (IL-16) in children with atopic/eczema dermatitis syndrome (AEDS): a novel serological marker of disease activity

BACKGROUND

Chemokines play a central role in atopic eczema/dermatitis syndrome (AEDS). Interleukin 16 (IL-16) has been described as a main cytokine involved in CD4+ cell recruitment during inflammation. Recently the influx of CD4+ lymphocytes has been related to the up-regulation of IL-16 in AEDS skin lesions. Circulating beta-chemokines (Eotaxin and RANTES) and IL-16 were investigated in children with AEDS to correlate their presence with the severity of the disease. We also measured serum levels of soluble CD30 (sCD30), a marker of Th2 immune responses related to AEDS disease activity.

METHODS

Serum levels of eotaxin, RANTES, IL-16 and sCD30 were measured by immunoenzymatic assay in paediatric patients with pure AEDS (pAEDS, n = 39); the severity of the disease was graded by SCORAD. Fifteen children with AEDS in presence of respiratory allergy (AEDS+A), 15 with allergic asthma (A) and 20 age-matched healthy donors were investigated as control groups.

RESULTS

When compared to normals, high amounts of Eotaxin and IL-16 were detected in sera of pAEDS (P = 0.002; P < 0.0001), AEDS+A (P = 0.02; P = 0.01) and A patients (P = 0.004; P = 0.03) with respect to normals. Serum levels of RANTES were also elevated in pAEDS patients, significantly higher than normals (P = 0.009), whereas no statistically significant differences could be detected between pAEDS and AEDS+A or A groups. IL-16 was progressively increased in the different stages of pAEDS, with a positive correlation between IL-16 and both SCORAD and sCD30 (P < 0.0001).

CONCLUSION

We suggest that IL-16 could serve as a useful marker of disease activity in childhood pAEDS.

Transcription from the RAG1 locus marks the earliest lymphocyte progenitors in bone marrow

Viable Lin(-) CD27(+) c-kit(Hi) Sca-1(Hi) GFP(+) cells recovered from heterozygous RAG1/GFP knockin mice progressed through previously defined stages of B, T, and NK cell lineage differentiation. In contrast to the GFP(-) cohort, there was minimal myeloid or erythroid potential in cells with an active RAG1 locus. Partial overlap with TdT(+) cells suggested that distinctive early lymphocyte characteristics are not synchronously acquired. Rearrangement of Ig genes initiates before typical lymphoid lineage patterns of gene expression are established, and activation of the RAG1 locus transiently occurs in a large fraction of cells destined to become NK cells. These early lymphocyte progenitors (ELP) are distinct from stem cells, previously described prolymphocytes, or progenitors corresponding to other blood cell lineages.

Lack of evidence for aggregation-dependent enhancement of p56lck in the signal transduction upon major histocompatibility complex recognition by mature T cells

The kinase activity of lymphocyte-specific tyrosine kinase p56lck (Lck) upon physiological major histocompatibility complex (MHC) recognition by normal mature T cells was examined. Recognition of the target MHC molecules by T cells induced phosphorylation of the zeta-chain without obvious enhancement of the background Lck activity. There was no sign of enhancement of Lck through putative T-cell receptor (TCR)-independent class II MHC/CD4 interactions either. As has been reported, cross-linking of CD4 molecules by antibodies induced a marked enhancement of Lck activity. However, it did not have an immediate relevance to TCR-mediated signal transduction, as judged from the lack of detectable de novo phosphorylation of zeta-chain and the absence of functional responses of T cells. These results strongly favour the model in which TCR-mediated signal transduction does not involve aggregation-dependent enhancement of Lck, suggesting that the signal can be triggered simply by the recruitment of already active Lck with basal kinase activity through the formation of a TCR/MHC/CD4 ternary complex.

Cytokines of birds: conserved functions--a largely different look

Targeted disruptions of the mouse genes for cytokines, cytokine receptors, or components of cytokine signaling cascades convincingly revealed the important roles of these molecules in immunologic processes. Cytokines are used at present as drugs to fight chronic microbial infections and cancer in humans, and they are being evaluated as immune response modifiers to improve vaccines. Until recently, only a few avian cytokines have been characterized, and potential applications thus have remained limited to mammals. Classic approaches to identify cytokine genes in birds proved difficult because sequence conservation is generally low. As new technology and high throughput sequencing became available, this situation changed quickly. We review here recent work that led to the identification of genes for the avian homologs of interferon-alpha/beta (IFN-alpha/beta) and IFN-gamma, various interleukins (IL), and several chemokines. From the initial data on the biochemical properties of these molecules, a picture is emerging that shows that avian and mammalian cytokines may perform similar tasks, although their primary structures in most cases are remarkably different.

Il-9 stimulates release of chemotactic factors from human bronchial epithelial cells

Interleukin (IL)-9 is a T helper 2 cytokine implicated as a candidate gene and contributor to human asthma. We hypothesized that the inflammatory potential of bronchial epithelium is affected by its local environment and explored this hypothesis with respect to the effect of IL-9 on bronchial epithelium. We investigated the response of primary and immortalized human bronchial epithelial cells to IL-9 stimulation with respect to the release of T-cell chemoattractant factors. In response to IL-9, the HBE4-E6/E7 cell line, but not BEAS-2B cells, released the T-cell chemoattractants IL-16 and regulated on activation, normal T cells expressed and secreted (RANTES) in a dose-dependent fashion. We found a similar dose response to IL-9 in primary cells from bronchial brushings of healthy subjects and that nearly all of the T-cell chemoattraction was attributable to IL-16 and RANTES. Reverse transcriptase/polymerase chain reaction of BEAS-2B, HBE4-E6/E7, and primary cells from two subjects revealed messenger RNA for IL-9 receptor (IL-9R) alpha but not in BEAS-2B cells. Fluorescence-activated cell sorter analysis of HBE4-E6/E7 and primary cells confirmed surface expression of the IL-9 receptor. Costimulation of both cell types with IL-9 and antibody to either gamma-common chain or IL-9Ralpha completely blocked the release of T-cell chemoattractant activity, confirming the primary role of a functioning IL-9 receptor for IL-9 signaling in HBE4-E6/E7 and primary bronchial epithelial cells. We conclude that IL-9 is a stimulus for airway epithelial cell release of T-cell chemoattractant factors, which in turn may modulate the immune response in allergic airway inflammation.

Nef triggers a transcriptional program in T cells imitating single-signal T cell activation and inducing HIV virulence mediators

Gene expression profiling was used to explore the role of Nef in HIV. Nef induces a transcriptional program in T cells that is 97% identical to that of anti-CD3 T cell activation. This program is inhibited in the presence of cyclosporin. A requirement for TCR zeta and ZAP-70 is demonstrated for formation of the complete profile. Among eight factors particular to the anti-CD3 activation profile are IL16 and YY1, negative regulators of HIV transcription. In contrast, Nef exclusively upregulates factors positively regulating HIV, including Tat-SF1, U1 SNRNP, and IRF-2. New genes associated with Nef include CDK9, the induction of which enhances Tat function. Thus, Nef acts as a master switch early in the viral life cycle, forcing an environment conducive to dynamic viral production.

Immunopathogenesis of human immunodeficiency virus: implications for immune-based therapies

Human immunodeficiency virus (HIV) infection leads to a state of CD4 lymphopenia and generalized immune activation with subsequent development of opportunistic infections and neoplasms. The use of highly active antiretroviral treatment has dramatically improved the clinical outcome for HIV-infected patients, but the associated cost and toxicity and the eventual development of drug resistance have underscored the need for additional therapeutic strategies. Immune-based therapies, such as treatment with cytokines or immunosuppressants, adoptive immunotherapy, and therapeutic immunizations, are being intensely investigated as potential supplements to antiretroviral therapy. Although much data have been generated as a result of these efforts, to date there has been little evidence of the clinical efficacy of these strategies. Randomized clinical studies remain critical in evaluating the clinical significance and the role of immune-based therapies in the therapeutic armamentarium against HIV.