Enhanced endothelial cell adhesion of human cerebrospinal fluid lymphocytes

Micrometer-sized thread-like and/or spherical particles in the first fraction of cerebrospinal fluid in patients with bipolar disorder

OBJECTIVES

Scanning electron microscopy (SEM) is a powerful tool to identify pathogenic factors for which sensitive tests are lacking. The technique has been used to recognize structures in the cerebrospinal fluid (CSF) of patients with schizophrenia. The aim of this study was to use SEM to screen for potential particles in CSF in bipolar disorder.

METHODS

Fresh CSF samples from 56 euthymic bipolar patients, 31 bipolar I disorder and 25 bipolar II disorder, were compared to CSF samples from 20 controls. SEM of two portions of 200 microL filtered CSF was performed; the first 0.6 mL of CSF and the following 12 mL. The microscopic structures were identified and the quantity and patterns were rated by two independent researchers.

RESULTS

Quantitative SEM examinations showed that of the 56 patients, 11 were free of any SEM structures in CSF, while 45 patients displayed morphological structures in the first 0.6 mL of CSF. By contrast, only 2 patients showed structures in the second CSF fraction drawn from the following mixed 12 mL of CSF. In total, 45 of the 56 patients had either thread-like, spherical, or both structures in the CSF, compared to none of the 20 controls.

CONCLUSIONS

The identified particles in the first fraction of CSF have previously not been described in patients with bipolar disorder. Hypothetically, the amount of SEM structures in CSF, from none to many, might correlate to the degree of the alleged underlying disease processes in the central nervous system in patients with bipolar disease.

Importance of IFN-γ-Mediated Expression of Endothelial VCAM-1 on Recruitment of CD8+T Cells into the Brain During Chronic Infection withToxoplasma gondii

Interferon-gamma (IFNgamma) is essential for preventing reactivation of chronic infection with Toxoplasma gondii in the brain. We examined the role of IFNgamma on lymphocyte and endothelial adhesion molecule expression and T cell recruitment into the brain during chronic infection with T. gondii in IFNgamma knockout (IFNgamma(-/-)) and wild-type (WT) mice. Although the number of cerebral vessels expressing intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) increased in both WT and IFNgamma(-/-) mice following infection, there were more VCAM-1(+) vessels in brains of infected WT than of infected IFNgamma(-/-) mice; in contrast, numbers of ICAM-1(+) vessels did not differ between strains. We did not detect endothelial E-selectin, P-selectin, MAdCAM-1, or PNAd in any of the brains. Significantly fewer CD8(+) T cells were recruited into brains of infected IFNgamma(-/-) than WT mice. Treatment of infected IFNgamma(-/-) mice with recombinant IFN-gamma restored the expression of VCAM-1 on their cerebral vessels and recruitment of CD8(+) T cells into their brains, confirming an importance of this cytokine for upregulation of VCAM-1 expression and CD8(+) T cell trafficking. In infected WT and IFNgamma(-/-) animals, almost all cerebral CD8(+) T cells were lymphocyte function-associated antigen-1 (LFA-1)(high), CD44(high), and CD62L(neg), and approximately 38% were alpha4beta1 integrin(+). In adoptive transfer of immune spleen cells, pretreatment of the cells with a monoclonal antibody (mAb) against alpha4 integrin markedly inhibited recruitment of CD8(+) T cells into the brain of chronically infected WT mice. These results indicate that IFN-gamma-induced expression of endothelial VCAM-1 and its binding to alpha4beta1 integrin on CD8(+) T cells is important for recruitment of the T cells into the brain during the chronic stage of T. gondii infection, although LFA-1/ICAM-1 interaction may also be involved in this process.

Chemokines and matrix metalloproteinase-9 in leukocyte recruitment to the central nervous system

Chemokines and matrix metalloproteinases (MMPs) play key roles in leukocyte migration across the blood-brain barrier (BBB) in infectious and inflammatory diseases, including multiple sclerosis (MS). In MS some chemokine receptors are expressed by an increased percentage of T cells in blood, the CSF concentration of chemokine ligands for these receptors is increased, and there is accumulation of T cells expressing relevant chemokine receptors in CSF and in the CNS parenchyma. Chemokine receptor expression patterns appear to reflect disease activity and disease stage in MS. MMPs are constitutively expressed or induced by proinflammatory cytokines and chemokines in leukocytes and CNS-resident cells. Several MMPs are expressed in MS plaques, and the CSF concentration of MMP-9 is increased in MS. The CSF concentration of MMP-9 may reflect disease activity in MS, and the CSF concentration of MMP-9 is higher in patients carrying the MS-associated HLA type DRB1 1501. We review how chemokines and MMP-9 may be involved in the pathogenesis of MS by controlling leukocyte migration between different functional compartments. Measuring expression of these molecules may find use as surrogate markers of disease activity in MS, and interfering with their function holds promise as a novel therapeutic strategy in MS.

Requirement of non-T cells that produce gamma interferon for prevention of reactivation of Toxoplasma gondii infection in the brain

We examined the mechanism of resistance against reactivation of infection with Toxoplasma gondii in the brain. BALB/c-background gamma interferon (IFN-gamma)-knockout (IFN-gamma(-/-)) and control mice were infected and treated with sulfadiazine beginning 4 days after infection for 3 weeks. After discontinuation of treatment, IFN-gamma(-/-) mice succumbed to toxoplasmic encephalitis (TE) and died, whereas control animals did not develop TE and survived. Adoptive transfer of immune spleen cells from infected control mice did not prevent development of TE or mortality in the IFN-gamma(-/-) mice. To examine whether the failure of the cell transfer to protect against TE is unique to IFN-gamma(-/-) mice, athymic nude and SCID mice that lack T cells were infected and injected with the immune spleen or T cells in the same manner as IFN-gamma(-/-) mice. Whereas control nude and SCID mice that had not received the immune cells developed severe TE and died after discontinuation of sulfadiazine, those that had received the cells did not develop TE and survived. Before cell transfer, IFN-gamma mRNA was detected in brains of infected nude and SCID but not in brains of IFN-gamma(-/-) mice. IFN-gamma mRNA was also detected in brains of infected SCID mice depleted of NK cells by treatment with anti-asialo GM1 antibody, and such animals did not develop TE after receiving immune T cells. Thus, IFN-gamma production by non-T cells, in addition to T cells, is required for prevention of reactivation of T. gondii infection in the brain. The IFN-gamma-producing non-T cells do not appear to be NK cells.

Proinflammatory cytokines in cerebrospinal fluid in repair of thoracoabdominal aorta

BACKGROUND

Little is known about alterations of cytokine levels in cerebrospinal fluid (CSF) during thoracoabdominal aortic surgery. We measured perioperative CSF cytokine levels to determine their clinical significances.

METHODS

Perioperative serum and CSF levels of cytokine were measured in 15 adult patients undergoing repair of the descending thoracic aorta (n = 4) or thoracoabdominal aorta (n = 11). All patients underwent prosthetic replacement and perioperative CSF drainage. Serum and CSF levels of tumor necrosis factor-alpha, Interleukin- (IL-) 1beta, IL-6, IL-8, IL-10, and IL-12 were measured before operation and at 0, 6, 12, 18, 24, 48, and 72 hours postoperatively using enzyme-linked immunosorbent assays.

RESULTS

There were no hospital deaths, but 1 patient suffered paraplegia. Cerebrospinal fluid IL-8 levels peaked at immediately after operation (751.7 +/- 42.1 pg/mL versus preoperative levels, 54.9 +/- 24.6 pg/mL; p < 0.001), and the higher levels persisted for 72 hours. In contrast, serum IL-8 levels did not change and remained lower than CSF levels. The patient with paraplegia had the highest CSF IL-8 levels throughout the study period. Serum and CSF levels of tumor necrosis factor-alpha, IL-1beta, IL-6, and IL-12 did not significantly change. Serum and CSF levels of IL-10 were significantly elevated after operation compared with preoperative levels. In contrast to IL-8, serum IL-10 levels surpassed CSF levels.

CONCLUSIONS

Cerebrospinal fluid IL-8 levels are significantly elevated in thoracoabdominal aortic operation, and may be the most sensitive to the inflammatory response in the ischemic spinal cord injury. Persistent elevation of CSF IL-8 levels may be predictive of further development of neurologic deficits, and a reduction of proinflammatory cytokine levels may be a beneficial effect of CSF drainage, but this requires further investigation.

Genes, cells and cytokines in resistance against development of toxoplasmic encephalitis

Toxplasma gondii is an intracellular protozoan parasite which invades various organs including the central nervous system. Immunity is crucial for preventing development of toxoplasmic encephalitis (TE) following infection. IFN-gamma-mediated immune response plays a central role in the resistance. The activation of microglia and astrocytes by IFN-gamma or a combination of this cytokine with TNF-alpha appears to be an important effector mechanism in the host immunity. GM-CSF, IL-1 beta and IL-6 may participate in this activation. iNOS is a molecule which mediates the protective activity of the activated murine microglia and human astrocytes; however, another unknown mechanism(s) not mediated by iNOS is involved in the activity of activated murine astrocytes and human microglia. IL-6 plays a protective role, at least in part, by up-regulating IFN-gamma production during the chronic stage of infection in mice. IL-6 also plays a role in regulating the infiltration of T cell subsets into the brain. IL-4 appears to play a protective role, but its role may differ depending on the strains of mice. In contrast to these protective cytokines, IL-10 may play a pathogenic role by down-regulating IFN-gamma production. The resistance against development of TE is under genetic control in both mice and humans. The Ld gene within the D region of the H-2 complex confers resistance in mice. In AIDS patients, HLA-DQ3 appears to be a genetic marker of susceptibility, and HLA-DQ1 appears to be a resistance marker. Strains (genetic variation) of T. gondii is another factor which affects the susceptibility of the host to the development of TE. The genotypes of the parasite may be important for determining the susceptibility. It is possible that the genes of the host and genetic variation of T. gondii affect immune response of the host to the parasite, and thereby contribute to determining the resistance against the development of TE.

Cytokine profile suggesting that murine cerebral malaria is an encephalitis

Cerebral malaria (CM) remains a poorly understood and life-threatening complication of malaria caused by the parasite Plasmodium falciparum. The discovery that murine CM caused by Plasmodium berghei ANKA and human CM are both characterized by production of inflammatory cytokines, especially tumor necrosis factor alpha (TNF-alpha), led to a revival of the suggestion that P. berghei CM may have value as a model of the human disease. In this study, quantitative reverse transcription-PCR was used to measure levels of message for 18S rRNA of P. berghei and 10 cytokines in the brains, livers, and spleens of mice during the induction and course of CM. A coordinated increase in RNA of parasite and proinflammatory cytokines was observed in the brains of mice in parallel with onset of CM. Levels of message for parasite, TNF-alpha, and gamma interferon increased in the brains of mice from day 5 to death on day 7. These changes were observed only in the brain, and message for other cytokines remained near baseline levels. This demonstrated that parasite sequestration does take place in the brains of mice with CM. Histologically, CM was characterized by widespread damage to the microvasculature in the brain with focal infiltration of inflammatory cells. The pattern of cytokine production in the brain is characteristic of other murine encephalitides.

Impaired resistance to the development of toxoplasmic encephalitis in interleukin-6-deficient mice

The role of interleukin-6 (IL-6) in the pathogenesis of toxoplasmic encephalitis (TE) was examined by using IL-6-targeted mutant (IL-6(-/-)) mice. At 4 and 8 weeks after infection with the ME49 strain of Toxoplasma gondii, significantly greater numbers of T. gondii cysts and areas of inflammation associated with tachyzoites were observed in brains of IL-6(-/-) mice than in those of control mice. Large areas of necrosis were observed only in brains of IL-6(-/-) mice. Tachyzoites were frequently detected in the areas of necrosis, suggesting that necrosis was caused by proliferation of the parasite. These results indicate that IL-6 is protective against development of TE by preventing formation of T. gondii cysts and proliferation of tachyzoites in brains of infected mice. Whereas in brains of control mice, large numbers of inflammatory cells were always observed in areas where tachyzoites were detected, in brains of IL-6(-/-) mice, only small numbers of inflammatory cells were observed in many areas with tachyzoites. Lymphocyte preparations isolated from brains of infected control mice had significantly higher ratios of gamma/delta T cells and CD4+ alpha/beta T cells but lower ratios of CD8+ alpha/beta T cells compared to those of infected IL-6(-/-) mice. There were no differences in the ratios of these T-cell subsets in spleens between these mice. The amounts of mRNA for gamma interferon (IFN-gamma) detected by reverse transcriptase PCR were significantly smaller in brains of IL-6(-/-) mice than in those of control mice, whereas amounts of IL-10 mRNA were greater in the former than in the latter. IL-6 mRNA was detected only in infected control mice. The protective activity of IL-6 against development of TE appears to be through its ability to stimulate IFN-gamma production and induce infiltration and accumulation of different T-cell subsets in brains of infected mice.