Selective Deletion of Heparan Sulfotransferase Enzyme, Ndst1, in Donor Endothelial and Myeloid Precursor Cells Significantly Decreases Acute Allograft Rejection.

Early damage to transplanted organs initiates excess inflammation that can cause ongoing injury, a leading cause for late graft loss. The endothelial glycocalyx modulates immune reactions and chemokine-mediated haptotaxis, potentially driving graft loss. In prior work, conditional deficiency of the glycocalyx-modifying enzyme N-deacetylase-N-sulfotransferase-1 (Ndst1f/f TekCre+) reduced aortic allograft inflammation. Here we investigated modification of heparan sulfate (HS) and chemokine interactions in whole-organ renal allografts. Conditional donor allograft Ndst1 deficiency (Ndst1-/-; C57Bl/6 background) was compared to systemic treatment with M-T7, a broad-spectrum chemokine-glycosaminoglycan (GAG) inhibitor. Early rejection was significantly reduced in Ndst1-/- kidneys engrafted into wildtype BALB/c mice (Ndst1+/+) and comparable to M-T7 treatment in C57Bl/6 allografts (P < 0.0081). M-T7 lost activity in Ndst1-/- allografts, while M-T7 point mutants with modified GAG-chemokine binding displayed a range of anti-rejection activity. CD3+ T cells (P < 0.0001), HS (P < 0.005) and CXC chemokine staining (P < 0.012), gene expression in NFκB and JAK/STAT pathways, and HS and CS disaccharide content were significantly altered with reduced rejection. Transplant of donor allografts with conditional Ndst1 deficiency exhibit significantly reduced acute rejection, comparable to systemic chemokine-GAG inhibition. Modified disaccharides in engrafted organs correlate with reduced rejection. Altered disaccharides in engrafted organs provide markers for rejection with potential to guide new therapeutic approaches in allograft rejection.

Atrial Fibrillation Ablation Increases Inflammation-Chemokine Modulation Suppresses Activation of Leukocytes Isolated after Ablation.

AIMS: Atrial fibrillation (AF) ablation is associated with increased circulating markers of inflammation. Innate immune or inflammation pathways up-regulate mononuclear cell responses and may increase the risk for recurrent arrhythmia. Chemokines and serine protease coagulation pathways both activate innate immune responses. Here, we measured inflammatory markers in peripheral blood samples from patients after cryoballoon and/or radiofrequency pulmonary vein isolation and assessed the capacity for the inhibition of chemokine and serine protease pathways to block cell activation. METHODS: Markers of inflammation were measured in 55 patients immediately before and one day after AF ablation. Peripheral blood mononuclear cells (PBMCs) isolated from 19 patients were further tested for responsiveness to two anti-inflammatory proteins ex vivo using fluorescence assays and RT-qPCR analysis of gene expression. RESULTS: White blood cells (WBC), C-reactive protein, fibrinogen and troponin T levels were significantly elevated after ablation. PBMCs isolated from the circulating blood had increased activation with Phorbol 12-myristate 13-acetate. Cell activation, as measured by membrane fluidity, was blunted after treatment with a broad-spectrum chemokine modulating protein, M-T7, which interferes with chemokine/glycosaminoglycan (GAG) interactions, but not by Serp-1, a serine protease inhibitor (serpin) that targets both thrombotic and thrombolytic pathway proteases. Differential gene expression changes in the apoptotic pathway were identified with M-T7 and Serp-1. CONCLUSIONS: Patients undergoing AF ablation have significantly increased inflammatory markers. Inhibition of chemokine signaling, but not serine proteases, reduced the activation of monocytes isolated from patients, in vitro. Targeting chemokines have the potential to reduce post-ablation activation of circulating leukocytes.

Reactive Center Loop (RCL) Peptides Derived from Serpins Display Independent Coagulation and Immune Modulating Activities.

Serpins regulate coagulation and inflammation, binding serine proteases in suicide-inhibitory complexes. Target proteases cleave the serpin reactive center loop scissile P1-P1' bond, resulting in serpin-protease suicide-inhibitory complexes. This inhibition requires a near full-length serpin sequence. Myxomavirus Serp-1 inhibits thrombolytic and thrombotic proteases, whereas mammalian neuroserpin (NSP) inhibits only thrombolytic proteases. Both serpins markedly reduce arterial inflammation and plaque in rodent models after single dose infusion. In contrast, Serp-1 but not NSP improves survival in a lethal murine gammaherpesvirus68 (MHV68) infection in interferon γ-receptor-deficient mice (IFNγR(-/-)). Serp-1 has also been successfully tested in a Phase 2a clinical trial. We postulated that proteolytic cleavage of the reactive center loop produces active peptide derivatives with expanded function. Eight peptides encompassing predicted protease cleavage sites for Serp-1 and NSP were synthesized and tested for inhibitory function in vitro and in vivo. In engrafted aorta, selected peptides containing Arg or Arg-Asn, not Arg-Met, with a 0 or +1 charge, significantly reduced plaque. Conversely, S-6 a hydrophobic peptide of NSP, lacking Arg or Arg-Asn with -4 charge, induced early thrombosis and mortality. S-1 and S-6 also significantly reduced CD11b(+) monocyte counts in mouse splenocytes. S-1 peptide had increased efficacy in plasminogen activator inhibitor-1 serpin-deficient transplants. Plaque reduction correlated with mononuclear cell activation. In a separate study, Serp-1 peptide S-7 improved survival in the MHV68 vasculitis model, whereas an inverse S-7 peptide was inactive. Reactive center peptides derived from Serp-1 and NSP with suitable charge and hydrophobicity have the potential to extend immunomodulatory functions of serpins.

Ebola virus glycoprotein Fc fusion protein confers protection against lethal challenge in vaccinated mice.

Ebola virus is a Filoviridae that causes hemorrhagic fever in humans and induces high morbidity and mortality rates. Filoviruses are classified as "Category A bioterrorism agents", and currently there are no licensed therapeutics or vaccines to treat and prevent infection. The Filovirus glycoprotein (GP) is sufficient to protect individuals against infection, and several vaccines based on GP are under development including recombinant adenovirus, parainfluenza virus, Venezuelan equine encephalitis virus, vesicular stomatitis virus (VSV) and virus-like particles. Here we describe the development of a GP Fc fusion protein as a vaccine candidate. We expressed the extracellular domain of the Zaire Ebola virus (ZEBOV) GP fused to the Fc fragment of human IgG1 (ZEBOVGP-Fc) in mammalian cells and showed that GP undergoes the complex furin cleavage and processing observed in the native membrane-bound GP. Mice immunized with ZEBOVGP-Fc developed T-cell immunity against ZEBOV GP and neutralizing antibodies against replication-competent VSV-G deleted recombinant VSV containing ZEBOV GP. The ZEBOVGP-Fc vaccinated mice were protected against challenge with a lethal dose of ZEBOV. These results show that vaccination with the ZEBOVGP-Fc fusion protein alone without the need of a viral vector or assembly into virus-like particles is sufficient to induce protective immunity against ZEBOV in mice. Our data suggested that Filovirus GP Fc fusion proteins could be developed as a simple, safe, efficacious, and cost effective vaccine against Filovirus infection for human use.

Beta-galactosylceramide alters invariant natural killer T cell function and is effective treatment for lupus.

NZB/W female mice spontaneously develop systemic lupus, an autoantibody mediated disease associated with immune complex glomerulonephritis. Natural killer (NK) T cells augment anti-dsDNA antibody secretion by NZB/W B cells in vitro, and blocking NKT cell activation in vivo with anti-CD1 mAb ameliorates lupus disease activity. In the current study, we show that beta-galactosylceramide reduces the in vivo induction of serum IFN-gamma and/or IL-4 by the potent NKT cell agonist alpha-galactosylceramide and reduces NKT cell helper activity for IgG secretion. Treatment of NZB/W mice with the beta-galactosylceramide ameliorated lupus disease activity as judged by improvement in proteinuria, renal histopathology, IgG anti-dsDNA antibody formation, and survival. In conclusion, beta-galactosylceramide, a glycolipid that reduces the cytokine secretion induced by a potent NKT cell agonist ameliorates lupus in NZB/W mice.

Protection against malaria due to innate immunity enhanced by low-protein diet.

Mice were fed ad libitum with a normal diet (25% protein) or low-protein diets (0-12.5% protein) for a wk and then infected with a nonlethal or lethal strain of Plasmodium yoelii, that is, blood stage infection. The same diet was continued until recovery. Mice fed with a normal diet showed severe parasitemia during nonlethal infection, but survived the infection. They died within 2 wk in the case of lethal infection. However, all mice fed with low-protein diets survived without apparent parasitemia (there were small peaks of parasitemia) in cases of both nonlethal and lethal strains. These surviving mice were found to have acquired potent innate immunity, showing the expansion of NK1.1 -TCRint cells and the production of autoantibodies during malarial infection. Severe combined immunodeficiency (scid) mice, which lack TCRint cells as well as TCRhigh cells, did not survive after malarial infection of lethal strain of P. yoelii, even when low-protein diets were given. These results suggest that low-protein diets enhanced innate immunity and inversely decreased conventional immunity, and that these immunological deviations rendered mice resistant against malaria. The present outcome also reminds us of our experience in the field study of malaria, in which some inhabitants eventually avoided contracting malaria even after apparent malarial infection.

Changes in fluoride sensitivity during in vitro senescence of normal human oral cells.

We have previously reported that sodium fluoride (NaF) showed slightly higher cytotoxicity against human oral tumor cell lines than normal human oral cells. Possible changes in the NaF sensitivity of three normal human oral cell types (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF) during in vitro ageing were investigated in the present study. When these cells were subcultured at 1:4 split ratio every week, their saturation density declined with increasing population doubling level (PDL), and they ceased to divide when they reached 20 PDL. Mitochondrial function, evaluated by MTT stainability per cell basis, was elevated at the terminal phase. NaF dose-dependently reduced the viable cell number, but did not show any beneficial (growth promoting) effect (so-called "hormesis") at lower concentrations. NaF produced large DNA fragments, without induction of internucleosomal DNA fragmentation, possibly due to weak activation of caspases -3, -8 and -9. Higher concentrations of NaF were required to reduce the number of viable senescent cells than younger cells, indicating that cells become resistant to cytotoxicity of NaF with in vitro ageing.

Tumor-specific cytotoxicity of 3,5-dibenzoyl-1,4-dihydropyridines.

In search of compounds which show tumor-specific cytotoxic activity, two 3,5-dibenzoyl-1, 4-dihydropyridines (GB5, GB12) were found to show one or two orders higher cytotoxic activity against human tumor cell lines (squamous cell carcinoma HSC-2, HSC-3, submandibular gland carcinoma HSG, promyelocytic leukemia HL-60) than human normal cells (gingival fibroblast HGF, pulp cells HPC, periodontal ligament fibroblasts HPLF). GB5 and GB12 weakly induced several apoptosis-associated properties, such as internucleosomal DNA fragmentation, and activation of caspases -3, -8 and -9, in both HL-60 and HSC-2 cells. Western blot analysis showed that GB5 and GB12 transiently increased the expression of both anti-apoptotic protein (Bcl-2) and proapoptotic proteins (Bax and Bad) in HL-60 cells. ESR spectroscopy showed these compounds did not produce any detectable amount of radicals, nor scavenged superoxide (generated by hypoxanthine-xanthine oxidase reaction) or nitric oxide (generated by 1-hydroxy-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene), suggesting that the induction of cytotoxic action is not via a radical-mediated reaction. The present study suggests that GB5 and GB12 may induce non-apoptotic cell death in tumor cell lines.

Hydroquinone-induced apoptosis in HL-60 cells.

To clarify the mechanisms by which hydroquinone (HQ; 1,4-benzenediol) produces apoptosis, HQ-induced cytotoxicity, intemucleosomal DNA fragmentation, activation of superoxide dismutase (SOD), expression of Mn and Cu/ZnSOD mRNA and activation of caspase-3, -8 and -9 were investigated in the human promyelocytic leukemic cell line HL-60. Electrophoresis and activity staining of the SOD-enriched fraction showed that HQ reduced MnSOD activation more than Cu/ZnSOD activation, suggesting that it induces mitochondrial dysfunction at an early stage of apoptosis. Furthermore, the expression of MnSOD mRNA was suppressed to a greater extent than that of Cu/ZnSOD mRNA, implying that HQ causes apoptosis by inhibiting MnSOD induction. Release of cytochrome c and activation of procaspase-3 and -9, but not of procaspase-8, occurred more rapidly (as early as 6 h) in HQ-treated cells, suggesting that HQ activates the intrinsic pathway of apoptosis. Addition of the antioxidant N-acetyl-L-cysteine (NAC) significantly reduced the cytotoxicity of HQ. At a concentration that was cytotoxic to 50% of the cells (approximately 0.05 mM), HQ activated caspase-3; this effect was reduced in the presence of NAC. Interestingly, higher concentrations of HQ (0.1-0.2 mM) caused direct cell death; however, when combined with 5 mM NAC, the activation of caspase-3 was strongly enhanced, suggesting the promotion of apoptosis. The activation of caspase-3 by HQ/NAC combinations suggests that NAC, a precursor of intracellular glutathione synthesis, acts as a co-catalyst during HQ-induced apoptosis.

Structure-activity relationships of alpha, beta-unsaturated ketones as assessed by their cytotoxicity against oral tumor cells.

A series of simple alpha, beta-unsaturated carbonyl compounds (1-26) was characterized for their cytotoxic profiles against oral human normal and tumor cells. Several cycloalkenones showed potent cytotoxic activities against human oral squamous cell carcinoma HSC-2 cell line. Among them, 4,4-dimethyl-2-cyclopenten-1-one (12) exhibited low cytotoxic activity against a normal human cell, gingival fibroblast HGF, and displayed higher tumor-specific cytotoxicity (SI value = CC50 (HGF)/CC50 (HSC-2) = 4.0). The cytotoxicities of the unsaturated lactones were moderately tumor-specific (SI = 1.5-1.9). Agarose gel electrophoresis showed that the induction of internucleosomal DNA fragmentation in human promyelocytic leukemia cell HL-60 is dependent on the structure of alpha, beta-unsaturated carbonyl compounds. Fluorometric protease assay showed that some, but not all compounds, activated the caspase 3 in a dose-dependent manner. All alpha, beta-unsaturated carbonyl compounds studied did not activate caspases 8 and 9. The cytotoxic activity of alpha, beta-unsaturated carbonyl compounds was profoundly reduced in the presence of N-acetylcysteine. The study suggests that the presence of a non sterically hindered Michael acceptor seems to be an essential structural requirement for the cytotoxic activity in alpha, beta-unsaturated ketones.

Induction of apoptosis by beta-diketones in human tumor cells.

A variety of beta-diketones were evaluated for their cytotoxic profiles against oral human normal and tumor cells. Among 22 compounds (BD1-22) tested, the cytotoxicity of 3-formylchromone (BD17) (CC50=7.8 microg/mL) against human oral squamous cell carcinoma (HSC-2) cells was higher than that of curcumin (CC50=23.6 microg/mL). Tumor cell-specific cytotoxicity was also detected in BD17 which exhibited little cytotoxic activity against a normal human cell, gingival fibroblast (HGF). (-)-3- (BD13) (CC50=21.7 microg/mL) and (+)-3-(Trifluoroacetyl)camphor (BD12) (CC50=29.7 microg/mL) are enantiomers and showed cytotoxicity comparable to curcumin and dibenzoylmethane (BD2) (CC50=22.5 microg/mL). BD13 did not induce DNA fragmentation in HL-60 cells nor activate caspase 3, 8 and 9 in both HL-60 and HSC-2 cells, regardless of the presence or absence of FeCl3. On the other hand, BD17 was found to induce apoptosis in HSC-2 and HL-60 cells, as judged by internucleosomal DNA fragmentation, caspase 3, 8 and 9 activation and dysfunction of mitochondrial membrane potential. The cytotoxic activity of BD13, BD17 and curcumin was significantly reduced by chelation with FeCl3. The tumor-specific cytotoxicity and apoptosis-inducing activity of BD17 against human tumor cells undoubtedly warrant further studies of its efficacy as a cancer chemotherapeutic agent.

Cytotoxic activity of deferiprone, maltol and related hydroxyketones against human tumor cell lines.

Hydroxyketone chelators, deferiprone (HK1), maltol (HK3) and their related compounds (HK2, 4-8), were characterized for their cytotoxic profiles against oral human normal and tumor cells. Most hydroxyketones except HK6 showed relatively higher tumor-specific cytotoxicity. Deferiprone (HK1), which showed the highest tumor specificity, had 10 times higher cytotoxicity than maltol (HK3) in both human promyelocytic leukemia HL-60 and human oral squamous cell carcinoma HSC-2 cell lines. The cytotoxic activity of HK1 against HL-60 and HSC-2 cells was reduced in the presence of FeCl3, while that of HK3 was significantly increased by FeCl3. Agarose gel electrophoresis showed that HK1 induced internucleosomal DNA fragmentation in HL-60 cells, but the addition of FeCl3 inhibited the DNA fragmentation. HK3 did not induce DNA fragmentation in HL-60 cells, regardless of the presence or absence of FeCl3. In HSC-2 cells, HK1 and 3 did not induce DNA fragmentation in the presence or absence of FeCl3. Colorimetric protease assay showed that HK1 activated the caspase 3, 8 and 9 in HL-60 cells. On the other hand, HK3 did not activate the caspase 3, 8 and 9 in HL-60 cells, but activated the caspase 3 only slightly in the presence of FeCl3. HK1 and 3 also activated the caspase 3, 8 and 9 in HSC-2 cells, but to a lesser extent. The present study suggested that the antitumor activity of hydroxyketones may be modified by Fe3+ concentration.

Effect of antioxidants, oxidants, metals and saliva on cytotoxicity induction by sodium fluoride.

We have recently found that millimolar concentrations of sodium fluoride (NaF) induced apoptotic cell death, characterized by caspase activation and DNA fragmentation, in tumor cell lines. This finding paved the way to investigating the interaction between NaF and the oral environment. As an initial step, we investigated redox compounds, metals and saliva, which may modify the cytotoxic activity of NaF against a human oral squamous cell carcinoma cell line (HSC-2). The minimum exposure time to NaF required for cytotoxicity induction was 8 hours. Noncytotoxic concentrations of antioxidants (sodium ascorbate, gallic acid, epigallocatechin gallate, chlorogenic acid, curcumin, superoxide dismutase, catalase), oxidants (hydrogen peroxide, sodium hypochlorite), metals (CuCl, CuCl2, FeCl2, FeCl3, CoCl2) or saliva neither protected against, nor enhanced the cytotoxic activity of NaF. Cytotoxic concentrations of these compounds produced somewhat additive, but not synergistic, effects on the cytotoxicity of NaF. ESR analysis demonstrated that NaF did not apparently change the radical intensity of sodium ascorbate and gallic acid, measured under alkaline conditions. During the cell death induction in human promyelocytic leukemia HL-60 cells by NaF, the consumption of glucose rapidly declined, followed by a decline in the consumption of major amino acids. The present study suggests that the cytotoxic activity of NaF is not regulated by the redox mechanism, but rather linked to the rapid decline in glucose consumption at early stage.

Onset of hepatic erythropoiesis after malarial infection in mice.

Plasmodium yoelii-infected erythrocytes were injected into mice with or without 6.5 Gy irradiation. This irradiation suppressed erythropoiesis and induced severe immunosuppression. However, these mice showed a rather delayed infection, suggesting that fresh erythrocytes may become malarial targets. In other words, malarial infection did not persist without newly generated erythrocytes in mice. We then examined erythropoiesis in the liver and bone marrow of mice with malaria. Surprisingly, erythropoiesis began in the liver. At this time, the serum level of erythropoietin (EPO) was prominently elevated and the EPO mRNA also became detectable in the kidney. Many clusters of red blood cells appeared de novo in the parenchymal space of the liver. These results revealed that malarial infection had a potential to induce the onset of hepatic erythropoiesis in mice.

Expansion of unconventional T cells with natural killer markers in malaria patients.

Immunological states during human malarial infection were examined. In parallel with parasitemia and anemia, granulocytosis was induced in the blood of patients, especially those infected with Plasmodium (P.) falciparum. At that time, the level of lymphocytes remained unchanged or slightly increased in the blood. However, the distribution of lymphocyte subsets was modulated, showing that the proportion of CD56(+)T cells, CD57(+)T cells, and gammadeltaT cells (i.e. all unconventional T cells) had increased in patients infected with P. falciparum or P. vivax. This phenomenon occurred at the early phase of infection and disappeared in the course of recovery. The data from patients with multiple attacks of P. vivax infection showed that there was no augmentation of these responses. In adult cases, the increase in the proportion of unconventional T cells seemed to closely parallel disease severity. However, all these responses were weak in children, even those infected with P. falciparum. In conjunction with accumulating evidence from mouse malaria experiments, the present results suggest that the immunological state induced by malarial infection might mainly be an event of unconventional T cells and that the immunological memory might not be long-lasting, possibly due to the properties of unconventional T cells.

Effect of endodontic agents on cytotoxicity induction by sodium fluoride.

We investigated six endodontic agents for their ability to induce apoptosis and modify the cytotoxic activity of NaF against human squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines. Four Group I agents (Form Cresol, Cam Phenic, Eucaly Soft, GC Fuji Varnish), but not two Group II agents (Caviton, Canals-N), induced internucleosomal DNA fragmentation and activated caspases 3, 8 and 9 in HL-60 cells. Only Cam Phenic among these agents additively enhanced the cytotoxic activity of NaF in HSC-2 and HL-60 cells. Form Cresol and Cam Phenic reduced the glucose consumption at early stage, possibly due to their toxic effect. Amino acid analysis suggests that the higher cytotoxicity of Form Cresol may be derived, at least in part, from its oxidizing action.

Effect of antitumor agents on cytotoxicity induction by sodium fluoride.

We have recently found that sodium fluoride (NaF) induced apoptotic cell death in tumor cell lines. We investigated here whether 6 popular antitumor compounds modify the cytotoxic activity of NaF against human squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines. Cytotoxic concentrations of cisplatin, etoposide, doxorubicin or peplomycin (tentatively termed as Group I compounds), but not methotrexate and 5-FU (tentatively termed as Group II compounds), enhanced the cytotoxic activity of NaF. NaF and Group I compounds induced internucleosomal DNA fragmentation in HL-60 cells, whereas Group II compounds were inactive even in the presence of NaF. Most Group I compounds except doxorubicin (which induced DNA fragmentation less effectively than others) activated caspase 3 more efficiently than Group II compounds. Caspase 8 (involved in non-mitochondrial extrinsic pathway) and caspase 9 (involved in mitochondrial intrinsic pathway) were also activated, but to a much lesser extent. NaF reduced the glucose consumption at early stage, possibly by inhibition of glycolysis, whereas cisplatin and etoposide reduced the glucose consumption at later stage, suggesting that early decline of glucose consumption is rather specific to NaF.

Tissue-specific expansion of NKT and CD5+B cells at the onset of autoimmune disease in (NZBxNZW)F1 mice.

Natural killer T (NKT) cells and CD5(+)B cells were searched for in various immune organs of autoimmune prone (NZBxNZW)F(1) (NZB/W F(1)) mice. The number of lymphocytes increased in the liver, spleen, and peritoneal cavity after the onset of disease (at the age of 30 weeks) while the number of thymocytes decreased at that time. Prominent changes of lymphocyte subsets were seen in the liver and peritoneal cavity, namely, expansion of IL-2Rbeta(+)TCRalpha beta(int) cells in the liver and of CD5(+)B220(+) cells in the peritoneal cavity. The majority of TCRalpha beta(int) cells in the liver were NK1.1(+), and CD5(+)B cells in the peritoneal cavity were CD1d(+). Proteinuria became prominent in NZB/W F(1) mice with the progression of disease. In parallel with this progression, the proportion of NKT cells decreased slightly in the liver, but their absolute number remained at a high level in this organ. These NKT cells were CD4(+) and used an invariant chain of Valpha14Jalpha281 for TCRalpha. Reflecting the elevation of CD5(+)B cells, autoantibodies against hepatocyte cytoplasmand denatured DNA were detected in sera. Although NKT cells are known to be immunoregulatory cells in some autoimmune mice, the present results raise the possibility that NKT cells as well as CD5(+)B cells might be associated with the onset of autoimmune diseases in NZB/W F(1) mice. Indeed, NKT cells in F(1) mice had a high potential to induce autoimmune-like inflammationwhen alpha-galactosylceramide was administered or when active NKT cells were transferred into young F(1) mice.

Essential role of extrathymic T cells in protection against malaria.

Athymic nude mice carry neither conventional T cells nor NKT cells of thymic origin. However, NK1.1(-)TCR(int) cells are present in the liver and other immune organs of athymic mice, because these lymphocyte subsets are truly of extrathymic origin. In this study, we examined whether extrathymic T cells had the capability to protect mice from malarial infection. Although B6-nu/nu mice were more sensitive to malaria than control B6 mice, these athymic mice were able to survive malaria when a reduced number of parasitized erythrocytes (5 x 10(3) per mouse) were injected. At the fulminant stage, lymphocytosis occurred in the liver and the major expanding lymphocytes were NK1.1(-)TCR(int) cells (IL-2Rbeta(+)TCRalphabeta(+)). Unconventional CD8(+) NKT cells (V(alpha)14(-)) also appeared. Similar to the case of B6 mice, autoantibodies (IgM type) against denatured DNA appeared during malarial infection. Immune lymphocytes isolated from the liver of athymic mice which had recovered from malaria were capable of protecting irradiated euthymic and athymic mice from malaria when cell transfer experiments were conducted. In conjunction with the previous results in euthymic mice, the present results in athymic mice suggest that the major lymphocyte subsets associated with protection against malaria might be extrathymic T cells.