Memory cells specific for myelin oligodendrocyte glycoprotein govern the transfer of experimental autoimmune encephalomyelitis (101.26)

Multiple sclerosis (MS) is a chronic, inflammatory disease of the central nervous system thought to be initiated by CD4+ T cells specific for myelin antigens. Experimental autoimmune encephalomyelitis (EAE), a model of MS, is induced in susceptible mouse strains by immunization with myelin antigens such as myelin oligodendrocyte glycoprotein (MOG). MOG35-55-specific T cell receptor transgenic (2D2) mice are susceptible to EAE following immunization with MOG peptide. To better understand the role of T cells in EAE initiation, we explored several approaches for effecting adoptive transfer of EAE using 2D2 T cells. Surprisingly, despite robust proliferation and production of IFN-γ and IL-17 following a variety of culture conditions, EAE was not transferred. Only when 2D2 whole splenocyte preparations contained CD44+ T cells and were Th1-differentiated using MOG peptide and IL-12 did they reliably transfer EAE. Further, we found that CD44hiCD62Llo effector/memory CD4+ T cells are likely responsible for disease transfer due to up-regulation of the adhesion molecule CD44 following differentiation. We also observed a sex dimorphism in 2D2 mice with males transferring more severe EAE, associated with a larger population of effector/memory CD4+ T cells in males compared to females. Given the importance of MOG in MS pathogenesis, mechanistic insights into adoptively transferred EAE by MOG-specific Th1 cells could prove valuable in MS research.

Enhanced T cell proliferation, Th17 differentiation and unaltered IL-10 production lead to marginally enhanced development of experimental autoimmune encephalomyelitis in EBI3-deficient mice (114.12)

Epstein-Barr virus-induced gene 3 (EBI3) encoded protein can form heterodimers with IL-27P28 and IL-12P35 to form IL-27 and IL-35. IL-27 and IL-35 may influence autoimmunity through inhibiting Th17 differentiation, and facilitating the inhibitory roles of Foxp3+ Treg cells, repectively. In this study we have evaluated the development of experimental autoimmune encephalomyelitis (EAE) in EBI3-deficient mice that lack both IL-27 and IL-35. We found that MOG peptide immunization resulted in marginally enhanced EAE development in EBI3-deficient C57BL6 and 2D2 TCR transgenic mice. EBI3-deficiency resulted in significantly increased proliferation and Th17 differentiation of MOG-specific CD4 T cells in the peripheral lymphoid organs and in the central nervous system (CNS). However, IL-10 production was not affected or even enhanced in the peripheral lymphoid organs or the CNS of EBI3-deficient mice. Treg cells from EBI3-deficient 2D2 mice had reduced capacity of inhibiting proliferation of 2D2 T cells. Taken together, we have found that EBI3-deficiency results in marginally enhanced EAE severity, which is associated with enhanced T cell proliferation and Th17 differentiation. However, the relatively milder EAE enhancement and lack of impact on IL-10 production by EBI3-deficiency suggest that alternative signaling pathways (presumably IL27P28-related) can partially compensate for EBI3-deficiency in EBI3-/- mice.

miRNA modulation of T cell phenotype in Multiple Sclerosis (167.3)

Pro-inflammatory T cells mediate autoimmune demyelination in Multiple Sclerosis (MS). However, the factors driving their development and MS susceptibility are obscure. We investigated how miRNAs, newly described as post-transcriptional regulators of gene expression, contribute to pathogenic T cell differentiation in MS. We profiled miRNA expression in naïve CD4+ T cells of healthy (n=8) and untreated MS (n=22) donors. miR-128, miR-27a/b and miR-340 were increased in naïve CD4+ T cells from MS patients. miR-128, -27a/b and -340 directly suppressed the pro-Th2 factor Bmi1, resulting in decreased GATA-3 expression. miR-340 additionally suppressed the Th2 cytokine IL-4. Overall, these miRNAs suppressed Th2 and enhanced pro-inflammatory Th1 responses. In addition, transfection of myelin-specific T cells with these miRNAs worsened EAE while treatment of MS patient cells with miRNA inhibitors led to the restoration of Th2 responses. These findings link miR-128, -27ab and -340 overexpression in MS patients’ naïve CD4+ T cells to the pro-inflammatory T cell differentiation observed in MS and illustrate the biological significance and therapeutic potential of these miRNAs.

MicroRNA-29 controls Th1 bias of CD4+ T cells in multiple sclerosis (167.5)

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system initiated by autoreactive CD4+ T cells of a T-helper (Th)1 and Th17 phenotype. Identifying novel factors that control Th differentiation will lead to a better understanding of MS pathogenesis and the development of new therapeutic strategies. MicroRNAs (miRs) are small non-coding RNAs that negatively regulate post-transcriptional gene expression. Dicer-deficient CD4+ T cells that lack miRs produce more of the Th1-associated cytokine IFN-γ; however, the specific miR(s) responsible for controlling Th1 programming have not been defined. Using in silico target prediction algorithms, we identified miR-29 as a factor that could potentially regulate multiple genes in the Th1 pathway. We confirmed that miR-29 directly targets T-bet and IFN-γ, and gain- and loss-of-function experiments demonstrated the ability of miR-29 to modulate Th1 polarization. Importantly, we found that naïve CD4+ T cells from MS patients express lower basal levels of miR-29 than controls. We further established an inverse relationship between basal expression of miR-29 and expression of T-bet/IFN-γ following activation of MS patient T cells. These results identify miR-29 as a novel regulator of Th1 differentiation and function, and implicate low miR-29 as an MS susceptibility factor. Restoring miR-29 may therefore be a powerful therapeutic modality in MS and other Th1-driven autoimmune diseases.

Macrophage migration inhibitory factor promotes central nervous system pathology through local microglial activation and macrophage trafficking (60.3)

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). It is reported that cerebrospinal fluid from MS patients during relapse contains higher levels of MIF than samples collected during remission. While the potent pro-inflammatory properties of MIF are well established, the precise contribution to neuroinflammation is not well defined. We have previously shown that despite their ability to generate pathogenic T cells, MIF-/- mice fail to develop experimental autoimmune encephalomyelitis (EAE), and have reduced CNS pathology. These findings suggest that MIF acts within the CNS to potentiate disease progression. We observed that MIF-treated microglia upregulate inflammatory mediators associated with MS and EAE including IL-1, IL-6, TNF-α, iNOS, and CCL2, and exhibit morphological changes consistent with activation. We extended these findings in vivo, performing stereotactic spinal microinjection of rMIF into naïve mice, which resulted in targeted microglial reactivity and cellular infiltration. To determine the role of MIF in the CNS during EAE, we examined the ability of rMIF spinal microinjection to restore CNS pathology in MIF-/- mice. Notably, rMIF microinjection was sufficient to restore CNS pathology in EAE-resistant MIF-/- mice following induction of EAE. Taken together, these studies implicate MIF as a CNS inflammatory mediator that may contribute to the development and maintenance of MS lesions.

Endothelial IL-1R1 is a critical mediator of EAE pathogenesis

Interleukin-1 (IL-1) has been implicated in the disease progression of multiple sclerosis (MS). In the animal model of MS, experimental autoimmune encephalomyelitis (EAE), the induction of disease is significantly attenuated in mice lacking the type I IL-1 receptor (IL-1R1). In this study, we created a transgenic mouse (eIL-1R1 kd) in which IL-1R1 expression is knocked down specifically in endothelial cells. Induction of EAE in eIL-1R1 kd mice results in a decrease in incidence, severity and delayed onset of EAE. In addition, eIL-1R1 kd mice show significant decrease in VCAM-1 expression and diminished CD45(+) and CD3(+) infiltrating leukocytes in the spinal cord in animals challenged with EAE. Further, IL-1 and IL-23 stimulate IL-17 production by splenocytes from both wild type and the eIL-1R1 kd animals. Similarly, IL-1 and IL-23 synergistically stimulate splenocytes proliferation in these two strains of animals. After immunization with MOG(79-96), although eIL-1R1 kd mice displayed greatly reduced clinical scores, their splenocytes produced IL-17 and proliferated in response to a second MOG challenge, similar to wild type animals. These findings indicate a critical role for endothelial IL-1R1 in mediating the pathogenesis of EAE, and describe a new model that can be used to study endothelial IL-1R1.

Exosomes mediate pregnancy-associated suppression of central nervous system inflammation in a murine model of multiple sclerosis (87.7)

Multiple sclerosis (MS) is thought to be a cell-mediated autoimmune disease that ultimately leads to demyelination and severing of nerve axons within the CNS. It is known that pregnancy suppresses MS relapses, particularly during the third trimester. We have recapitulated this observation in murine experimental autoimmune encephalomyelitis (EAE). A serum factor is implicated as responsible for EAE suppression during pregnancy. We observed that serum exosomes, nano-sized facilitators of intercellular communication, are significantly more concentrated during late pregnancy in mice. To determine which proteins are expressed in pregnancy versus control-derived exosomes, we performed differential gel electrophoresis followed by mass spectrometry. Several identified proteins have important functions in both the immune and CNS compartments. Proteins enriched in pregnancy exosomes facilitate the local action of corticosterone, scavenge oxygen-derived free radicals, inhibit matrix metalloproteases, and provide survival signals to oligodendrocytes, the myelinating cell of the CNS. Thus, we explored the effects of exosomes on EAE and on immune and CNS cells, including analyzing inflammatory cytokine profiles of myelin-specific T cells and the proliferation and maturation of oligodendrocyte precursor cells. Determining the mechanism by which pregnancy exosomes suppress inflammation and examining their neuroprotective properties will aid in the development of novel MS therapies.

MicroRNAs: modulators of T cell phenotype in multiple sclerosis (143.57)

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system mediated by autoreactive CD4+ T cells of a Th1 and Th17 phenotype. Identifying novel factors that control Th differentiation will lead to a better understanding of disease pathogenesis and the development of new therapeutic strategies. MicroRNAs (miRs) are a class of small non-coding RNAs that negatively regulate post-transcriptional gene expression. MiRs have an established role in immune system homeostasis, and profiling studies have found differential expression of miRs in autoimmune diseases, including MS. Dicer-deficient CD4+ T cells that lack miRs produce more cytokine upon stimulation. Together these data indicate the miR(s) are responsible for controlling cytokine expression and act as negative regulators of inflammation. However, the specific miR(s) responsible for modulating inflammatory cytokine production and Th programming have not been defined. Using target prediction algorithms, we identified miRs predicted to target genes that mediate Th1 specification and function. We have validated these miR-target pairs using gain- and loss-of-function experiments in human Th1-polarized cells. We have also profiled the expression of these miRs in specific CD4+ T cell subsets from MS patients. Our results identify miRs that modulate Th developmental programming and effector function and whose expression is altered in MS. These miRs may be useful immunomodulatory treatments or biomarkers in MS.

Developing regulatory dendritic cells with the pregnancy estrogen estriol (98.11)

In addition to inflammatory (immunogenic) capabilities, DCs have a potent role in regulating inflammation and immunity. We have found that DCs from estriol (E3) treated mice are activated regulatory DCs (regDCs). Specifically, these splenic E3 regDCs have elevated CD80, CD86, PD-L1, PD-L2, B7-H3 and B7-H4, hypo-produce IL-12, inhibit T cell proliferation and, upon adoptive transfer, protect mice from EAE through promoting Th2 responses. In these studies, we generated regDCs in vivo and in vitro and developed an in vitro correlate to splenic E3 regDCs. Mice given murine Flt3L (mFL)-secreting cells expanded both CD11b-CD11c+ and CD11b+CD11c+ cells, demonstrated mononuclear hyperplasia within bone marrow, lymph nodes and spleens and E3-exposed DCs were phenotypically similar to human Flt3L (hFL) E3 regDCs. Bone marrow DCs (BM-DCs) were generated with mFL, hFL or GM-CSF with or without E3. E3 inhibited FL BM-DC differentiation while GM-CSF BM-DCs were less affected. Phenotypic evaluation showed elevated CD80, CD86, PD-L1 and PD-L2 and CD4+ T cells proliferated less when cultured with E3 BM-DCs. These results demonstrate that E3 generates regDCs in vitro and in vivo and demonstrate an in vitro correlate to in vivo generated E3 regDCs. Generation of regDCs has important therapeutic applications in autoimmunity and inflammatory diseases.

Macrophage migration inhibitory factor promotes central nervous system pathology in a model of neuroinflammation (35.8)

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Cerebrospinal fluid collected from MS patients during relapse was found to contain greater levels of macrophage migration inhibitory factor (MIF) than samples collected during remission. We have shown that induction of experimental autoimmune encephalomyelitis (EAE) in MIF-deficient mice results in reduced clinical signs and CNS inflammatory infiltrates relative to wild type controls. However, there was no difference in T cell function in the periphery between the two groups. These findings suggest that MIF acts within the CNS to potentiate disease progression. The potent pro-inflammatory properties of MIF are well established; however, the precise contribution of MIF to neuroinflammation is not well defined. MIF is expressed by many cell types in the CNS including infiltrating macrophages and resident microglia, suggesting that MIF may enhance the inflammatory environment of MS lesions. To assess the contribution of MIF to CNS inflammation, primary microglial cultures were treated with increasing doses of rMIF, which upregulated inflammatory mediators associated with MS and EAE: IL-1β, iNOS, and CCL2. We are currently exploring the role of MIF in vivo using an intraspinal model of neuroinflammation. Taken together, these data suggest that inhibition of MIF may serve as a therapeutic strategy for resolving CNS inflammation.

Macrophage migration inhibitory factor is a therapeutic target in treatment of non-insulin-dependent diabetes mellitus

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in the pathogenesis of a variety of autoimmune inflammatory diseases. Here, we investigated the role of MIF in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) using MIF(-/-) mice and a mouse model of streptozotocin (STZ)-induced NIDDM. Following single injection of STZ, MIF(+/+) BALB/c mice showed a significant increase in blood glucose levels, developed polyuria, and succumbed to disease. In contrast, no such increase in blood glucose was observed in MIF(-/-) BALB/c mice treated with STZ. These mice produced significantly less inflammatory cytokines and resistin as compared with MIF(+/+) mice and failed to develop clinical disease. Finally, oral administration of a small-molecule MIF antagonist, CPSI-1306, to outbred ICR mice following induction of NIDDM significantly lowered blood glucose levels in the majority of animals, which was also associated with a significant reduction in the levels of the proinflammatory cytokines IL-6 and TNF-alpha in the sera. Taken together, these results demonstrate that MIF is involved in the pathogenesis of NIDDM and is a therapeutic target to treat this disease.

Physical and observational practice afford unique learning opportunities

In 2 experiments, the authors studied the effectiveness of physical and observational practice on learning and the effect on learning of combining physical practice and observation, as compared with providing physical practice alone. In Experiment 1, retention and transfer performance of 30 university students after physical, observational, or no practice were contrasted. Consistent with findings from other studies, the retention results indicated that observational practice is inferior to physical practice. The transfer data indicated no differences between observation and physical practice groups. In Experiment 2, retention and transfer performance of 30 participants in physical and combined (alternating physical and observational) practice groups were contrasted. The retention results showed no differences between the combined and physical practice groups, but the combined group performed significantly better than the physical practice group on the transfer test. Those findings suggest that a combination of observation and physical practice permits unique opportunities for learning beyond those available via either practice regimen alone.

Pharmacokinetics and pharmacodynamics of the leukotriene B4 receptor antagonist CP-105,696 in man following single oral administration

AIMS

CP-105,696, (+)-1-(3S,4R)-[3-(4-phenylbenzyl)-4-hydroxy-chroman-7-yl] cyclopropane carboxylic acid is a potent, novel LTB4 receptor antagonist advanced to clinical trials to determine its efficacy in inflammatory diseases. The pharmacokinetics and pharmacodynamics of CP-105,696 were investigated in healthy male volunteers following oral administration of single doses of 5 to 640 mg.

METHODS

Forty-eight subjects participated in a randomized, double-blind, parallel group study. Plasma and urine concentrations of CP-105,696 were determined at intervals after drug administration. As an indication of LTB4 receptor antagonism following oral administration of CP-105,696, the inhibiton of LTB4-induced upregulation of the neutrophil cell surface complement receptor (CR3), CD11b/CD18, was monitored at 4 h following drug administration using an ex vivo whole blood flow cytometry assay.

RESULTS

Cmax and AUC(0, infinity) increased in a dose-related manner. Respective mean Cmax values were 0.54 to 30.41 microg ml(-1) following doses of 5 to 640 mg. Respective mean AUC(0, infinity) values were 1337 to 16819 microg ml(-1) h for the 40 to 640 mg dose groups. Plasma concentrations declined in a monoexponential manner, with terminal elimination half-lives ranging from 289 to 495 h. Group mean terminal elimination half-lives were dose-independent. Urinary excretion of unchanged drug accounted for < 1% of the administered dose. A linear relationship was observed between CP-105,696 plasma concentrations and inhibition of LTB4-mediated CD11b upregulation on human neutrophils in whole blood. CP-105,696 plasma concentrations of 5-6 microg ml(-1) were necessary to elicit a two-fold shift to the right of the LTB4 concentration response curve for CD11b upregulation.

CONCLUSIONS

These studies demonstrate pharmacologically significant LTB4-receptor antagonism following a single dose of CP-105,696 and pharmacokinetics consistent with once-daily dosing.

Effects of oral tolerance induction by myelin basic protein on Vbeta8+ Lewis rat T cells

Encephalitogenic T cells from Lewis rats use a restricted T cell receptor (TCR) gene combination, Vbeta8.2 and Valpha2. The oral administration of myelin basic protein (MBP) to Lewis rats prior to encephalitogenic challenge results in a marked inhibition of clinical neurologic signs of encephalitis, reduced central nervous system pathology, suppressed T cell reactivity to MBP, and decreased serum anti-MBP antibody responses. The present study determined the TCR Vbeta8 gene usage in rats rendered orally tolerant to MBP as compared with vehicle-fed or unfed controls. Total RNA was extracted from lymph node cells (LNC), Northern blots run, and hybridizations performed using a rat beta chain V region probe positive for Vbeta8.2. The results indicate that feeding MBP results in a decrease in Vbeta8+ TCR RNA expression in lymph nodes draining the site of encephalitogenic challenge. T cell proliferation was reduced in LNC of tolerized rats relative to control rats. No change in the Vbeta8+ TCR RNA expression or MBP reactivity was observed in the mesenteric lymph nodes (MLN) of vehicle-fed or MBP-fed rats, although an increase in cell number was found in the MLN of both groups. These results suggest that the mechanisms of orally induced tolerance involve local clonal deletion or migration of Vbeta8+ T cells, of which MBP-specific T cells are a part.

Gallium nitrate suppresses lupus in MRL/lpr mice

Gallium (Ga) nitrate, a drug which prevents a variety of experimental autoimmune diseases, was investigated in a murine model of systemic lupus erythematosus (SLE). In one experiment, female MRL/Mp lpr/lpr (MRL/lpr) mice were randomized into 2 groups of 6: 1) vehicle (trisodium citrate) and 2) Ga. Subcutaneous injections began at 3 weeks of age and continued weekly until the mice were euthanized a week after the thirteenth injection. The loading dose of Ga (calculated as elemental Ga) was 45 mg/kg, followed by 15 mg/kg/week. In another experiment (n = 18) with 3 males and 3 females per group, mice received 1) vehicle, 2) Ga x 1 (one 45 mg/kg dose), and 3) Ga x 13. In the experiment with 12 mice, axillary lymph nodes from Ga-treated mice were significantly smaller than those from vehicle-treated mice (91+/-42 and 360+/-358 mg respectively, mean+/-SD), and spleens as well as lymph nodes from the former showed significantly less lymphoid infiltrate. In the experiment with 18 mice, prescapular lymph nodes weighed 312+/-98, 217+/-52, and 42+/-34 mg, and spleens weighed 732+/-492, 409+/-164, and 192+/-93 mg in the groups which received vehicle, Ga x 1, and Ga x 13 respectively. Control mice had significantly more lymphoid infiltrates in the lungs, spleen, and lymph nodes and, unlike Ga x 13 mice, exhibited glomerulitis and renal vasculitis. Within groups, females developed more severe disease than males. The Ga x 13 group had increased percentages of CD4-bearing and CD8-bearing lymphocytes in lymph nodes and increased CD4-bearing lymphocytes in the spleen, with an increased proliferative response to mitogen stimulation in vitro in lymph nodes, although not in the spleen. The Ga x 13 group also gained less weight and developed osteosclerosis. Although preliminary, our findings suggest that clinical trials with Ga in SLE are merited.

Treatment of human immunodeficiency virus infection with saquinavir, zidovudine, and zalcitabine. AIDS Clinical Trials Group

BACKGROUND

In patients with human immunodeficiency virus (HIV) infection, combined treatment with several agents may increase the effectiveness of antiviral therapy. We studied the safety and efficacy of saquinavir, an HIV-protease inhibitor, given with one or two nucleoside antiretroviral agents, as compared with the safety and efficacy of a combination of two nucleosides alone.

METHODS

In this double-blind trial, patients with HIV infection were randomly assigned to receive either saquinavir (1800 mg per day) plus both zidovudine (600 mg per day) and zalcitabine (2.25 mg per day) or zidovudine plus either saquinavir or zalcitabine. The 302 patients enrolled had CD4+ counts of 50 to 300 cells per cubic millimeter and had previously received zidovudine for a median of 27 months. The study lasted 24 weeks, with an optional double-blind extension period of an additional 12 to 32 weeks.

RESULTS

Ninety-six percent of the patients completed the 24-week study. In all three treatment groups, CD4+ cell counts rose at first and then fell gradually. The normalized area under the curve for the CD4+ count was greater with the three-drug combination than with either saquinavir and zidovudine (P=0.017) or zalcitabine and zidovudine (P<0.001). There were significantly greater reductions in plasma HIV with the three-drug combination than with the other regimens when peripheral-blood mononuclear cells were cultured for HIV and HIV RNA was assessed, and there were greater decreases in serum neopterin and beta2-microglobulin levels. There were no major differences in toxic effects among the three treatments.

CONCLUSIONS

Treatment with saquinavir, zalcitabine, and zidovudine was well tolerated. This drug combination reduced HIV-1 replication, increased CD4+ cell counts, and decreased levels of activation markers in serum more than did treatment with zidovudine and either saquinavir or zalcitabine. Studies are warranted to evaluate whether the three-drug combination will reduce morbidity and mortality.

Contextual dependencies during perceptual-motor skill acquisition: gone but not forgotten!

The development and resiliency of contextual dependencies developed during perceptual-motor skill acquisition was assessed. Incidental aspects of the stimulus used to instigate the production of previously practised typing sequences were manipulated during either an immediate or delayed retention test. The findings from the immediate test offered further support for the existence of contextual-dependent performance for perceptual-motor responding. However, the dependency was attenuated by using a delayed retention test. Experiment 2 pursued two alternative explanations for the diminished dependency effect revealed in Experiment 1. In Experiment 2 some subjects were explicitly encouraged to reinstate aspects of the incidental contextual information that was present during training prior to administration of a delayed test. The dependency present only in the immediate test in Experiment 1 reemerged after contextual reinstatement. The present data are discussed with respect to the inclusion of incidental contextual stimuli as part of the long-term sensorimotor memory representation.

Suppression of experimental autoimmune encephalomyelitis by gallium nitrate

We examined the effect of gallium (Ga) nitrate on the development of the development of experimental autoimmune encephalomyelitis (EAE). Weekly subcutaneous injections of 10-30 mg/kg prevented clinical signs as well as histopathological changes of EAE. The optimal timing of a single injection of Ga was 6 days after induction of EAE, with amelioration also apparent following a single injection on day 3 or 9 but not day 12. Ga administered in vivo suppressed myelin basic protein (MBP) and purified protein derivative-specific lymphocyte proliferative responses in vitro. Addition of Ga to MBP-specific T lymphocyte line cultures at various times after initiation of culture revealed that Ga exerts an effect at an early stage of cellular activation.

Magnetic resonance imaging of white matter lesions in HIV infection

Previous studies of the frequency of high-signal lesions in human immunodeficiency virus (HIV) infection have had methodological weaknesses regarding lack of control groups, differing machine strengths, and biased subject selection. To obtain a more accurate estimate of prevalence, MRI scans were performed on 243 HIV-positive and HIV-negative homosexual or bisexual men with no history of intravenous drug use. Axial T2-weighted (long TR/TE, spin-echo) MRI scans were rated blindly for presence of focal white matter high-signal lesions. Incidence of hyperintensities was low in all groups, although slightly higher in patients with AIDS, and was not associated with neuropsychological performance. The lower incidence of hyperintensities appears to relate to elimination of methodological problems in previous studies.

Lymphocyte supernatant-induced human monocyte tumoricidal activity: dependence on the presence of gamma-interferon

Recently, gamma-interferon (IFN-gamma) has been shown to be have the capacity to activate macrophages in several murine and human systems. The studies reported here were undertaken to determine the identity of the lymphokine responsible for activation of human monocytes to a tumoricidal state. Macrophage-activating factor (MAF) activity was assessed using a 24-h 51Cr release assay with human monocytes as effector cells and K-562 targets. Stimulated lymphocyte supernatants were produced by stimulation of peripheral blood mononuclear cells with concanavalin A in serum-free media. Interferon was detected in an antiviral assay. Four lines of evidence lead to the conclusion that MAF and IFN-gamma are identical in this system: (a) fractionation of stimulated lymphocyte supernatants by adsorption chromatography, followed by anion or cation exchange chromatography (Mono-S, Mono-Q columns), resulted in nearly identical elution profiles of MAF and IFN activities. All of the individual fractions containing MAF activity were found to contain IFN in amounts corresponding to MAF activity. (b) Monoclonal antibody specific for IFN-gamma neutralized the ability of stimulated lymphocyte supernatants to induce human monocyte tumoricidal activity. This antibody also neutralized the MAF activity of purified IFN-gamma but not alpha-interferon. (c) The biological MAF activity of activated lymphocyte supernatants and IFN-gamma were similar. Dilution versus MAF activity for IFN-gamma and stimulated lymphocyte supernatants exhibited identical slopes. Lymphocyte supernatants and IFN-gamma demonstrated similar MAF activity on three effector cells: monocytes, in vitro-differentiated macrophages, and dexamethasone-differentiated macrophages. (d) Analysis of supernatants produced by five antigen-stimulated human T-cell clones demonstrated coordinate production of MAF and IFN. These results provide compelling evidence for support of the concept that IFN-gamma is the major human lymphokine capable of inducing monocyte-macrophage tumoricidal activity.

Host immune responses after administration of inactivated Venezuelan equine encephalomyelitis virus vaccines--III. Kinetics for neutralizing antibody immunoglobulin class responses in donors and adoptively-immunized recipients

C57B16 mice were immunized with either live, attenuated TC-83 strain VEE virus vaccine or formalin-inactivated VEE vaccine combined with Bordetella pertussis. The kinetics of specific donor and adoptively-immunized recipient anti-VEE neutralizing antibody responses were studied. Donor mice immunized with either live or inactivated VEE virus vaccine combined with potent adjuvants develop specific anti-VEE IgM and IgG responses as early as 7 days post-immunization. Anti-VEE IgM antibody responses comprise the majority of anti-VEE neutralizing antibody at this early time period. By 14 to 21 days post-immunization, anti-VEE IgG responses predominated. When adoptively-immunized recipients were studied, the anti-VEE IgM to IgG predominance seen in donors early after administration was reversed, and for each time-period studied, recipients' serum anti-VEE antibody class responses consisted principally of IgG rather than IgM antibody. Since T-cells cooperation with B-cells is critical in the IgM-IgG antibody shift, these studies support the critical role T-cells exert in adoptive transfer in a murine model of experimental VEE infection. Furthermore, immunization with either live or inactivated VEE vaccine coupled to a potent adjuvant induce comparable donor and adoptively-immunized recipient anti-VEE antibody class responses.

Characterization of IgG-containing DEAE fractions of canine serum

A high-titered canine antilymphocyte serum was chromatographed on DE-52 cellulose and the fractions were assayed for cytotoxic activity. Although cytotoxicity was associated with the first 63% of the column effluent corresponding to fractions 1 through 7, significant activity (256) was demonstrable only in fractions 2, 3, 4, and 5. An immunoelectrophoretic study of fractions 1 through 5 showed only IgGa in fraction 1, IgGa and IgGb as electrophoretically separate arcs in fraction 2, and as electrophoretically inseparable arcs in fractions 3 through 5. Cytotoxicity is postulated to be associated with the IgGb subclass, since titers correspond with the distribution of IgGb in column fractions.