T lymphocytes promote the development of bone marrow-derived APC in the central nervous system

A "Drug-Dependent" Immune System Can Compromise Protection against Infection: The Relationships between Psychostimulants and HIV

Psychostimulant use is a major comorbidity in people living with HIV, which was initially explained by them adopting risky behaviors that facilitate HIV transmission. However, the effects of drug use on the immune system might also influence this phenomenon. Psychostimulants act on peripheral immune cells even before they reach the central nervous system (CNS) and their effects on immunity are likely to influence HIV infection. Beyond their canonical activities, classic neurotransmitters and neuromodulators are expressed by peripheral immune cells (e.g., dopamine and enkephalins), which display immunomodulatory properties and could be influenced by psychostimulants. Immune receptors, like Toll-like receptors (TLRs) on microglia, are modulated by cocaine and amphetamine exposure. Since peripheral immunocytes also express TLRs, they may be similarly affected by psychostimulants. In this review, we will summarize how psychostimulants are currently thought to influence peripheral immunity, mainly focusing on catecholamines, enkephalins and TLR4, and shed light on how these drugs might affect HIV infection. We will try to shift from the classic CNS perspective and adopt a more holistic view, addressing the potential impact of psychostimulants on the peripheral immune system and how their systemic effects could influence HIV infection.

Transplantation with Lewis bone marrow induces the reinstatement of cocaine-seeking behavior in male F344 resistant rats

One of the main challenges to understand drug addiction is defining the biological mechanisms that underlie individual differences in recidivism. Studies of these mechanisms have mainly focused on the brain, yet we demonstrate here a significant influence of the peripheral immune system on this phenomenon. Lewis (LEW) and Fischer 344 (F344) rats have different immunological profiles and they display a distinct vulnerability to the reinforcing effects of cocaine, with F344 more resistant to reinstate cocaine-seeking behavior. Bone marrow from male LEW and F344 rats was transferred to male F344 rats (F344/LEW-BM and F344/F344-BM, respectively), and these rats were trained to self-administer cocaine over 21 days. Following extinction, these animals received a sub-threshold primer dose of cocaine to evaluate reinstatement. F344/LEW-BM but not F344/F344-BM rats reinstated cocaine-seeking behavior, in conjunction with changes in their peripheral immune cell populations to a profile that corresponded to that of the LEW donors. After cocaine exposure, higher CD4⁺ T-cells and lower CD4⁺CD25⁺ T-cells levels were observed in F344/LEW-BM rats referred to control, and the splenic expression of Il-17a, Tgf-β, Tlr-2, Tlr-4 and Il-1β was altered in both groups. We propose that peripheral T-cells respond to cocaine, with CD4⁺ T-cells in particular undergoing Th17 polarization and generating long-term memory, these cells releasing mediators that trigger central mechanisms to induce reinstatement after a second encounter. This immune response may explain the high rates of recidivism observed despite long periods of detoxification, shedding light on the mechanisms underlying the vulnerability and resilience of specific individuals, and opening new perspectives for personalized medicine in the treatment of relapse.

Pediatric spontaneous pneumothorax

Spontaneous pneumothorax (SP) occurs when air enters the pleural space in the absence of a traumatic or iatrogenic etiology and is an uncommon phenomenon in the pediatric population. Although the typical presentation has been well described in the literature, much debate still surrounds the epidemiology, pathophysiology, diagnosis, and management of this condition in the pediatric population. To date, much of the emphasis in the pediatric literature has been on surgical options. Questions still remain regarding the true incidence of this disease in children, appropriate diagnostic imaging, and treatment recommendations for practitioners in the emergency department setting. This review of the evidence seeks to elaborate on current knowledge and clinical practice, as well as the applicability of adult recommendations to the pediatric population.

Cell-specific temporal infection of the brain in a simian immunodeficiency virus model of human immunodeficiency virus encephalitis

Increasing evidence supports early brain infection by human immunodeficiency virus (HIV). Definitive temporal studies determining when and within which brain cells viral DNA is present are lacking. This study utilized simian immunodeficiency virus (SIV)-infected macaques sacrificed at days 10, 21, 56, and 84 post inoculation. Laser-microdissection isolated pure perivascular macrophage, parenchymal microglia, and astrocyte populations. Nested polymerase chain reaction (PCR) and sequencing determined the presence and characteristics of SIV V3 and V1 env DNA from each population. At day 10, SIV DNA was detected in perivascular macrophage and astrocytes but not parenchymal microglia. gp41 expression was restricted to perivascular macrophage. At day 21, SIV DNA was not detected in any cell type. At day 56, SIV DNA was detectable in perivascular macrophage from one of two macaques, with no gp41 expression detected. At day 84 (morphologic and clinical encephalitis), SIV DNA was detected in all cell types, gp41 was only detected in perivascular macrophage and parenchymal microglia. The neurovirulent molecular clone, SIV/17E-Fr, was the only genotype identified in the brain cell populations. Early, productive brain SIV infection was transient and restricted to trafficking perivascular macrophage. During the nonencephalitic stage, there was a period of time when no SIV DNA could be detected in the brain cell populations. SIV was then seen to reenter the brain via infected perivascular macrophage, leading to productive infection of brain parenchymal macrophage/microglia with a terminal phase of encephalitis. These data challenge current notions of a HIV reservoir within latently infected, semipermanent brain cells and has significant implications for the timing and design of therapies to prevent HIV encephalitis (HIVE).

Magnetic brain stimulation upregulates adhesion and prevents Eae: MMP-2, ICAM-1, and VCAM-1 in the choroid plexus as a target

Clinical signs appearance and significant increases of ICAM-1 and MMP-2 expressions with the clusters of VCAM-1(+) immunoreactivity in the choroids plexus epithelium to transferred anti-myelin oligodendroglial antibodies into the third brain ventricle, indicate important role of choroids plexus in the induction of acute experimental autoimmune encephalomyelitis (EAE). Magnetic brain stimulation with AKMA micro-magnet flux density of 60 miliTesla, 5 mm in diameter, implanted upon the pineal gland (PG), immediately after antibody injection, significantly decreases the expression of MMP-2 and ICAM-1 in the choroids plexus of the rat brain and abruptly suppresses the induction of acute EAE.

Fatalities in natalizumab treatment--a 'no go' for leukocyte recirculation approaches?

Natalizumab (Tysabri), Biogen Idec/Elan) is a humanised neutralising antibody directed against alpha4 integrin expressed by leukocytes. Although it is an effective therapy for multiple sclerosis (MS), the serious adverse effect of progressive multifocal leukoencephalopathy (PML) resulted in its voluntary withdrawal from the market by Biogen Idec/Elan in February 2005. This has raised debates on whether PML was caused by blocking leukocyte trafficking-mediated immune suppression or by other effects through targeting alpha4 integrin per se. The authors propose that natalizumab-associated PML is a target-specific side effect predominantly due to the combination of: i) blocking leukocyte trafficking to peripheral organs resulting in reduced immune surveillance; ii) mobilisation of PML-causative JC virus-carrying bone marrow precursor cells and splenic marginal zone B cells; and iii) migration of these cells to sites of inflammation such as the brain. Therefore, combination of these effects is, so far, specific for the target alpha4 integrin and should not occur in general when interfering with other targets involved in leukocyte trafficking.

Brain microglia and blood-derived macrophages: molecular profiles and functional roles in multiple sclerosis and animal models of autoimmune demyelinating disease

Microglia and macrophages, one a brain-resident, the other a mostly hematogenous cell type, represent two related cell types involved in the brain pathology in multiple sclerosis and its autoimmune animal model, the experimental allergic encephalomyelitis. Together, they perform a variety of different functions: they are the primary sensors of brain pathology, they are rapidly recruited to sites of infection, trauma or autoimmune inflammation in experimental allergic encephalomyelitis and multiple sclerosis and they are competent presenters of antigen and interact with T cells recruited to the inflamed CNS. They also synthesise a variety of molecules, such as cytokines (TNF, interleukins), chemokines, accessory molecules (B7, CD40), complement, cell adhesion glycoproteins (integrins, selectins), reactive oxygen radicals and neurotrophins, that could exert a damaging or a protective effect on adjacent axons, myelin and oligodendrocytes. The current review will give a detailed summary on their cellular response, describe the different classes of molecules expressed and their attribution to the blood derived or brain-resident macrophages and then discuss how these molecules contribute to the neuropathology. Recent advances using chimaeric and genetically modified mice have been particularly telling about the specific, overlapping and nonoverlapping roles of macrophages and microglia in the demyelinating disease. Interestingly, they point to a crucial role of hematogenous macrophages in initiating inflammation and myelin removal, and that of microglia in checking excessive response and in the induction and maintenance of remission.

Role of Microglia and Macrophages in Eae

Microglia and macrophages are related cell types that play an important role in the pathogenesis of MS and EAE. This chapters reviews the role of these cells in the normal brain and their contribution to inflammatory demyelinating disease, including their role in antigen presentation, co-stimulation, and production of cytokines and other inflammatory mediators

Correlation between accelerated presbycusis and decreased immune functions

The aim of the current study is to analyze the relationship between presbycusis and the immune system, which is affected by pathogenic environments, and to devise a strategy for the prevention of presbycusis using the SAMP1 mouse, an animal model for accelerated senescence that shows both immunological dysfunction and hearing loss caused by the impairment of spiral ganglion cells in the cochlea. When these mice were bred in different pathogenic environments, we found that the development of age-related diseases such as presbycusis was delayed in the mice bred under clean conditions. Prednisolone administration showed no significant prevention of the development of presbycusis in the mice, suggesting that autoimmune mechanisms are not involved in the acceleration of presbycusis. It is conceivable that pathogen-induced infections impose a severe stress on the host, impairing the host's immune functions. A reduction in the number of pathogens may therefore prevent the acceleration of the aging process. These findings suggest that not only the gene backgrounds but also immune functions affect the development of presbycusis in SAMP1 mice. Further studies into the relationship between systemic immune functions and the neuro-generation system may provide additional information about the treatment for age-related diseases.

Nonmyelin-specific T cells accelerate development of central nervous system APC and increase susceptibility to experimental autoimmune encephalomyelitis

Previously we demonstrated that both myelin-specific and nonmyelin-specific rat T cells were capable of accelerating the development of transplanted rat BM-derived APC in the CNS of SCID C.B-17/scid (SCID) mice. This suggested that nonmyelin-specific T cells might be capable of increasing susceptibility to EAE by increasing the number and function of APC in the CNS before disease induction. To assess this possibility, we evaluated disease incidence, day of onset, duration, mean peak severity, cumulative disease index, and histopathology in the presence or absence of nonmyelin-specific T cells. The results demonstrate an association between T cell responses to nonmyelin Ags, accelerated development of BM-derived CNS APC before disease induction, and heightened susceptibility to CNS inflammation mediated by myelin-specific T cells. This suggests that T cell responses to nonmyelin Ags can potentiate CNS inflammation by elevating the functional presence of CNS APC.

Intrathecal Fas ligand infusion strengthens immunoprivilege of central nervous system and suppresses experimental autoimmune encephalomyelitis

Fas ligand (FasL) is an essential molecule strongly expressed in some immunoprivileged sites, but is expressed at very low levels in normal CNS. In this study, acute experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats with guinea pig myelin basic protein. Intrathecal infusion of recombinant FasL before EAE onset dose dependently suppressed acute EAE and alleviated pathological inflammation in lumbosacral spinal cord. This treatment greatly increased apoptosis in CNS inflammatory cells, but did not inhibit systemic immune response to myelin basic protein. Systemic administration of a similar dose of rFasL was ineffective. In vitro, encephalitogenic T cells were highly sensitive to rFasL-induced cell death, and activated macrophages were also susceptible. In addition, in vitro rFasL treatment potentiated the immunosuppressive property of rat cerebrospinal fluid. We conclude that intrathecal infusion of rFasL eliminated the initial wave of infiltrating T cells and macrophages, and therefore blocked the later recruitment of inflammatory cells into CNS. Although Fas receptor expression was observed on spinal cord neurons, astrocytes, and oligodendrocytes, no damage to these cells or to the myelin structure was detected after rFasL infusion.

Prevention of accelerated presbycusis by bone marrow transplantation in senescence-accelerated mice

A substrain of the senescence-accelerated mouse (SAM), the SAMP1 mouse, is an animal model for accelerated senescence including the age-related acceleration of both immunological dysfunction and hearing loss caused by the impairment of spiral ganglion cells. In the present study, we examine whether the accelerated presbycusis can be prevented by allogeneic BMT. Young SAMP1 (H-2(k)) mice were irradiated with 9 Gy and then reconstituted with bone marrow cells from normal BALB/c (H-2(d)) mice. Allogeneic BMT was found to prevent the development of immunological dysfunction, hearing loss, and apoptosis of spinal ganglion cells in SAMP1 mice. These findings indicate that some types of accelerated presbycusis do not result from defects in the cochlea, but do from defects in the hematopoietic stem cells (HSC) and immunocompetent cells derived from the HSC. If this is the case, either allogeneic BMT, which replaces abnormal HSC with normal HSC and reconstructs a normal immune system in the recipients, or autologous BMT using genetically modified bone marrow cells, could become a new strategy for the treatment of presbycusis.