CD4+ suppressor cells of autoimmune encephalomyelitis respond to T cell receptor-associated determinants on effector cells by interleukin-4 secretion.

We have previously demonstrated that CD4+ suppressor T cells (Ts) inhibit the secretion of interferon (IFN)-gamma, but not interleukin (IL)-2, by effector cells of experimental autoimmune encephalomyelitis (EAE). Moreover, CD4+ Ts appear to regulate IFN-gamma by secretion of transforming growth factor-beta. We now show that CD4+ Ts produce a lymphokine with IL-4 activity in response to a determinant associated with EAE effector cells. CD4+ Ts do not proliferate or secrete IFN-gamma, IL-2, or IL-4 in response to myelin basic protein, nor do CD4+ Ts proliferate or secrete IL-2 when co-cultured with irradiated EAE effector cells. Rather, CD4+ Ts secrete IL-4 when co-cultured with either irradiated effector spleen cells or irradiated encephalitogenic line cells. CD4+ Ts do not secrete IL-4 in response to OVA-primed spleen cells, suggesting that the suppressor cells recognize a determinant specific to encephalitogenic T cells. Furthermore, CD4+ Ts secrete IL-4 when cultured with synthetic T cell receptor (TcR) V beta 8, but not TcR V beta 14 peptide, in the presence of antigen-presenting cells. This response is major histocompatibility complex class II restricted as demonstrated by inhibition of the response with anti-class II monoclonal antibody. These results suggest that CD4+ Ts recognize a determinant associated with TcR on the surface of EAE effector cells and respond by secreting IL-4, in a manner analogous to the Th2 lymphocyte subtype.     

Central catecholamine neurotoxin administration. 1. Immunological changes associated with the suppression of experimental autoimmune encephalomyelitis

Central nervous system (CNS) depletion of norepinephrine (NE) using 6-hydroxydopamine (6-OHDA) prior to disease induction suppressed the clinical signs of experimental autoimmune encephalomyelitis (EAE). This treatment did not have an effect on the degree of mononuclear cell infiltration when spinal cord sections were examined and stained with hematoxylin and eosin, nor on serum levels of anti-myelin basic protein antibodies. However, investigation of the subpopulations of lymphoid cells within the perivascular lesions showed an increase in cells bearing the T suppressor cell phenotype, OX8+, in the 6-OHDA-treated EAE rats when compared to saline-control-treated EAE rats. Examination of other cellular subsets showed no differences in the numbers of T helper cells, macrophages, or B cells within the lesions of the two groups. Furthermore, histofluorescent estimation of catecholamines in spinal cord sections from 6-OHDA- and saline-control-treated EAE rats demonstrated that catecholamines were indeed depleted in the rats with suppressed clinical EAE. These findings suggest that 6-OHDA depletion of CNS NE may remove an effector amplification mechanism, or trigger a T suppressor cell mechanism, or both, leading to suppression of the effector phase of EAE, clinical paralysis.     

Nudging to donate organs: do what you like or like what we do?

An effective method to increase the number of potential cadaveric organ donors is to make people donors by default with the option to opt out. This non-coercive public policy tool to influence people’s choices is often justified on the basis of the as-judged-by-themselves principle: people are nudged into choosing what they themselves truly want. We review three often hypothesized reasons for why defaults work and argue that the as-judged-by-themselves principle may hold only in two of these cases. We specify further conditions for when the principle can hold in these cases and show that whether those conditions are met is often unclear. We recommend ways to expand nationwide surveys to identify the actual reasons for why defaults work and discuss mandated choice policy as a viable solution to many arising conundrums.

     

Chemokines and central nervous system disorders

Chemokines and their receptors are large families of inflammatory molecules responsible for a number of biologic functions including the accumulation of leukocytes at tissue sites. Over the past 8 years, a number of studies have indicated a role for chemokines in the pathogenesis of CNS inflammatory diseases. This minireview provides a brief summary of our current knowledge of chemokines and CNS inflammatory diseases including experimental autoimmune encephalomyelitis, multiple sclerosis, virus-induced demyelinating diseases, Alzheimer's disease, and central nervous system bacterial-induced diseases.     

CCR2 regulates development of Theiler's murine encephalomyelitis virus-induced demyelinating disease

Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, a murine model for multiple sclerosis, involves recruitment of T cells and macrophages to the CNS after infection. We hypothesized that CCR2, the only known receptor for CCL2, would be required for TMEV-induced demyelinating disease development because of its role in macrophage recruitment. TMEV-infected SJL CCR2 knockout (KO) mice showed decreased long-term clinical disease severity and less demyelination compared with controls. Flow cytometric data indicated that macrophages (CD45(high) CD11b(+) ) in the CNS of TMEV-infected CCR2 KO mice were decreased compared with control mice throughout disease. CD4(+) and CD8(+) T cell percentages in the CNS of TMEV-infected control and CCR2 KO mice were similar over the course of disease. There were no apparent differences between CCR2 KO and control peripheral immune responses. The frequency of interferon-gamma-producing T cells in response to proteolipid protein 139-151 in the CNS was also similar during the autoimmunity stage of TMEV-induced demyelinating disease. These data suggest that CCR2 is important for development of clinical disease by regulating macrophage accumulation after TMEV infection.     

Role of Chemokines in the Regulation of Th1/Th2 and Autoimmune Encephalomyelitis

Chemokines are low molecular weight chemotactic peptides that bind seven transmembrane-spanning, G protein-coupled receptors and deliver signals leading to T cell costimulation, hematopoeisis, cytokine expression, T cell differentiation, and integrin activation. Experimental autoimmune encephalomyelitis (EAE) is a CD4⁺ Th1-mediated demyelinating disease of the central nervous system (CNS) that serves as a model for multiple sclerosis (MS). A hallmark in the pathogenesis of this CNS demyelinating disease is the emigration of T cells and monocytes from the blood to the CNS. There are several considerations that suggest a role for chemokines in the influx of inflammatory cells and the resulting disease process including a tight temporal expression pattern with relationship to disease activity and prevention of disease development by in vivo neutralization. We review the evidence that temporal and spatial expressions of chemokines are crucial factors, complementing adhesion molecule upregulation, that regulate EAE and potentially MS disease activity as well as the functions of chemokines in Th1 and Th2 biology.     

Selective CC chemokine receptor expression by central nervous system-infiltrating encephalitogenic T cells during experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a CD4(+) T cell disease of the central nervous system (CNS) characterized by mononuclear cell infiltration, demyelination, and paralysis. Recent studies describing the relationship of chemokine expression with development of clinical disease have led to the hypothesis that distinct chemokine receptors corresponding to specific ligands are expressed by CNS-infiltrating antigen-specific encephalitogenic T cells as well as host-derived bystander T cells and monocytes. In an effort to study encephalitogenic T cell chemokine receptor expression, we examined CC chemokine receptor expression from resting, activated, and CNS-isolated CD4(+) T cells. CCR1, CCR2, CCR3, CCR5, CCR6, CCR7, and CCR8 mRNA is expressed by normal CD4(+) T cells. In vitro activated T cells expressed CCR1, CCR2, CCR3, CCR5, CCR6, CCR7, and CCR8 mRNA as well as CCR4. After EAE induction, CCR1 mRNA was expressed by donor-derived encephalitogenic and host-derived CD4(+) T cells isolated only from CNS and not from spleen. In vivo neutralization of the CCR1 ligand, macrophage inflammatory protein-1alpha (CCL3), resulted in less encephalitogenic CD4(+) T cell CNS infiltration. These results demonstrate the importance of CC chemokine receptor expression by CD4(+) encephalitogenic T cells for CNS infiltration and subsequent disease development.     

Suppression of clinical weakness in experimental autoimmune encephalomyelitis associated with weight changes, and post-decapitation convulsions after intracisternal-ventricular administration of 6-hydroxydopamine

Selective depletion of central nervous system norepinephrine (NE) by the neurotoxin 6-hydroxydopamine (6-OHDA) in rats subsequently inoculated with myelin basic protein (MBP) and complete Freund's adjuvant (CFA) produced experimental autoimmune encephalomyelitis (EAE) without the usual expected degree of weakness. The preservation of strength occurred in spite of continued weight loss. Post-decapitation myoclonic convulsive kick latency and kick number, which are known to depend on spinal cord NE, agreed well with the degree of weakness through the clinical disease course. The only difference between EAE groups was that the stronger 6-OHDA pretreated EAE animals did not have an elevated pons-medulla NE compared to saline intracisternal-ventricular (i.c.v.) pretreated controls. We conclude that 6-OHDA can influence the clinical course of weakness by interfering with central noradrenergic activity independent of other features associated with disease in EAE. This effect of 6-OHDA may be exerted through alteration of the blood-spinal cord barrier function and/or central nervous system blood flow.     

Down-regulation of TGF-beta1 production restores immunogenicity in prostate cancer cells

The objective of this study is to determine if a non-immunogenic Dunning's rat prostate cancer cell line, MATLyLu, can become immunogenic by reducing the endogenous production of TGF-beta1. An expression construct containing a DNA sequence in an antisense orientation to TGF-beta1 (TGF-beta1 antisense) was stably transfected into MATLyLu cells. Following transfection, cellular content of TGF-beta1 reduced from 70 to 10 pg per 2x10(4) cells and the rate of in vitro 3H-thymidine incorporation increased 3-5-fold. After subcutaneous injection of tumour cells into syngeneic male hosts (Copenhagen rats), the tumour incidence was 100% (15/15) for the wild type MATLyLu cells and cells transfected with the control construct, but only 43% (9/21, P< or =0.05) for cells transfected with TGF-beta1 antisense. However, when cells were injected into immunodeficient hosts (athymic nude rats), the incidence of tumour development was 100% (10/10) for both the wild type MATLyLu cells and cells transfected with the control construct and 90% (9/10) for cells transfected with TGF-beta1 antisense. These observations support the concept that MATLyLu cells are immunogenic, when the endogenous production of TGF-beta1 is down-regulated.     

Differential activation of astrocytes by innate and adaptive immune stimuli

The immunologic privilege of the central nervous system (CNS) makes it crucial that CNS resident cells be capable of responding rapidly to infection. Astrocytes have been reported to express Toll-like receptors (TLRs), hallmark pattern recognition receptors of the innate immune system, and respond to their ligation with cytokine production. Astrocytes have also been reported to respond to cytokines of the adaptive immune system with the induction of antigen presentation functions. Here we have compared the ability of TLR stimuli and the adaptive immune cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) to induce a variety of immunologic functions of astrocytes. We show that innate signals LPS- and poly I:C lead to stronger upregulation of TLRs and production of the cytokines IL-6 and TNF-alpha as well as innate immune effector molecules IFN-alpha4, IFN-beta, and iNOS compared with cytokine-stimulated astrocytes. Both innate stimulation and adaptive stimulation induce similar expression of the chemokines CCL2, CCL3, and CCL5, as well as similar enhancement of adhesion molecule ICAM-1 and VCAM-1 expression by astrocytes. Stimulation with adaptive immune cytokines, however, was unique in its ability to induce upregulation of MHC II and the functional ability of astrocytes to activate CD4(+) T cells. These results indicate potentially important and changing roles for astrocytes during the progression of CNS infection.