Entamoeba histolytica: chemoattractant activity for gerbil neutrophils in vivo and in vitro

The kinetics of the host's cellular response in the peritoneal cavity of gerbils toward axenic pathogenic and nonpathogenic Entamoeba histolytica strains were examined. Amebae contained in diffusion chambers or free in the peritoneum elicited a neutrophilic response accompanied by decreased levels of macrophages and lymphocytes. Pathogenic amebae (IP:0682:1 strain) elicited a neutrophilic response greater than the nonpathogenic DKB and "entamoeba-like" Laredo amebae. The neutrophil eliciting factor was found in high levels in disrupted freeze-thawed amebae (53% elicited neutrophils vs 8% for control), glutaraldehyde fixed amebae (45%) and amebic membranes (65%), and low levels in conditioned amebic medium (15%) and the supernatant fraction of amebae (16%). The factor was heat stable to high temperature (100 C for 30 min) and at various pH (6 to 9). The neutrophil eliciting factor in amebic membranes was lowered following pretreatment for 30 min with 1% immune and nonimmune gerbil or human sera (34-48% lowered neutrophil response vs control), acidic pH (less than 3, 69%), proteolytic digestion [trypsin (68%) and alpha-chymotrypsin (72%), 100 micrograms/ml], and 2% Triton X-100 (75%). Peritoneal neutrophils isolated following stimulation with amebic membranes or thioglycollate medium demonstrated higher chemotaxis in vitro toward live pathogenic amebae and amebic membranes (IP:0682:1 strain) compared to either the supernatant fraction or the nonpathogenic DKB or Laredo amebae. The results of this study indicate that membrane bound proteins of pathogenic amebae are chemotactic for gerbil neutrophils which may be important in the pathogenesis and pathology of amebiasis.     

Effective human defense against E. histolytica: high amoebicidal activity of lymphocytes and monocytes in amoebic liver abscess patients until 3 months follow-up

Adherence of pathogenic Entamoeba histolytica trophozoites mediated by Gal/GalNAc lectin is a prerequisite for killing na?ve T cells and monocytes but the activated T cells and monocyte derived macrophages (MDMs) not only resist the attack but can kill the parasite. In the present study, we have analysed the adherence and cytotoxicity of the immunecompetent cells from patients of amoebic liver abscess at the time of their diagnosis and after 3 months to elucidate the development of cell mediated cytotoxicity, a major mechanism of resistance to amoebic infection. The results show that CD3+ cells from amoebic liver abscess cases, when stimulated, in vitro, bound E. histolytica trophozoites with increased intensity and their viability was also increased. The activated lymphocytes (taken at 3 months post treatment) were also able to kill amoebae. MDMs bound amoebae with greater intensity than lymphocytes, until 3 months post infection. These MDMs were effective in killing approximately 40% amoebae which was significantly less than at the time of diagnosis but was very significant as compared to the controls. The data suggest that cell mediated cytotoxic responses are maximum until 1 month post treatment and are significantly reduced thereafter.     

Chemoattractant activity of Entamoeba histolytica for human polymorphonuclear neutrophils

The ability of axenic Entamoeba histolytica trophozoites and amoebic protein preparations to stimulate chemotaxis of human polymorphonuclear neutrophils (PMN) was evaluated. Virulent E. histolytica (strain HM1:IMSS) stimulated chemotaxis (delta distance = 0.55 +/- 0.02 mm, P less than 0.01 vs. control medium). Sonicated (100 micrograms protein/ml) or homogenized (500 micrograms protein/ml) virulent amoebae also significantly stimulated PMN chemotaxis, whereas preparations of the nonpathogenic "Entamoeba-like" Laredo strain did not stimulate chemotaxis. Preparations of subcellular fractions of E. histolytica demonstrated maximal stimulation of PMN chemotaxis existed in nonvesiculated membranes and the supernatant from plasma membranes.     

Entamoeba histolytica: impedance measurements and cytotoxicity in the presence of bepridil, verapamil, and cytochalasin D

Entamoeba histolytica, and invasive enteric protozoa, kills mammalian target cells by sequential adherence and cytolytic events. Using platinum plate electrodes with an alternating current source placed in a Wheatstone bridge circuit, the impedance (resistance to ion flow) of a cell suspension of axenic amebae (strain HM1-IMSS) was measured. The impedance of the amebic cell suspension, expressed as resistivity (in ohm-cm), was significantly greater than the test solution and increased with decreasing temperature or greater cell packing (P less than 0.01), indicating that the resistivity measurements reflected the impedance of the amebic surface membrane. Cytochalasin D (10 micrograms/ml), a microfilament inhibitor which inhibited amebic in vitro adherence and cytolysis of target Chinese hamster ovary (CHO) cells (P less than 0.001), also increased resistivity of the amebic suspension (P less than 0.01). Exposure of amebae to bepridil (10(5) M), a slow-channel blocker, inhibited amebic killing of target cells (P less than 0.01) and also increased the resistivity of the amebic suspension (P less than 0.01), but both to a lesser degree than cytochalasin D (P less than 0.001). In contrast, exposure of amebae to verapamil followed by washing had no effect on amebic killing of target cells or resistivity of the amebic suspension. The increased resistivity measured in cytochalasin D or following exposure to bepridil was not due to a change in cell density of the amebic suspension. These studies indicate that changes in impedance of the amebic surface membrane are produced by bepridil and cytochalasin D. The effect of these agents on membrane impedance may contribute directly to the concurrent observed alteration in amebic cytopathogenic capacity or may serve as a parallel marker for the cell membrane alterations induced by such pharmacologic agents which inhibit amebic microfilament function or calcium flux.     

Effect of iron on adherence and cytotoxicity of Entamoeba histolytica to CHO cell monolayers

Iron is an essential element for almost all living organisms. The possible role of iron for growth, adherence and cytotoxicity of Entamoeba histolytica was evaluated in this study. The absence of iron from TYI-S-33 medium stopped amebic growth in vitro. However, iron concentrations in the culture media of 21.4-285.6 microM did not affect the growth of the amebae. Although growth was not retarded at these concentrations, the adhesive abilities of E. histolytica and their cytotoxicities to CHO cell monolayer were correlated with iron concentration. Amebic adhesion to CHO cell monolayers was significantly reduced by low-iron (24.6 +/- 2.1%) compared with 62.7 +/- 2.8 and 63.1 +/- 1.4% of amebae grown in a normal-iron and high-iron media, respectively. E. histolytica cultured in the normal- and high-iron media destroyed 69.1 +/- 4.3% and 72.6 +/- 5.7% of cultured CHO cell monolayers, but amebae grown in the low-iron medium showed a significantly reduced level of cytotoxicity to CHO cells (2.8 +/- 0.2%). Addition of divalent cations other than iron to amebic trophozoites grown in the low-iron medium failed to restore levels of the cytotoxicity. However, when E. histolytica grown in low-iron medium were transferred to normal-iron medium, the amebae showed completely restored cytotoxicity within 7 days. The result suggests that iron is an important factor in the adherence and cytotoxicity of E. histolytica to CHO cell monolayer.     

Cytopathologic and genetic diagnosis of pulmonary amebiasis: a case report

BACKGROUND: Amebiasis is a parasitic infection with Entamoeba histolytica. Pulmonary amebiasis is rare since the infection is commonly manifested as amebic colitis or liver abscess. Most pleuropulmonary amebiasis is seen in patients with amebic liver abscesses. A pulmonary amebic lesion without either a liver abscess or amebic colitis is extremely rare. Thus, reported cases of sputum cytologic diagnosis of a pulmonary amebic lesion from a patient without a liver abscess are also very rare. CASE: A 53-year-old man presented with a dry cough and mild fever. Chest radiography revealed an abnormal solitary mass lesion in the right upper lung field. The clinical diagnosis was a bacterial lung abscess. Sputum cytologic examination demonstrated many trophozoites of E. histolytica. Following sputum cytodiagnosis, serologic tests revealed a slightly high but almost normal titer of IgG antibodies to E. histolytica, indicating the possible presence of the pathogen. Polymerase chain reaction (PCR) using E. histolytica-specific primers for DNA extracted from the sputum sample revealed specific DNA product. CONCLUSION: Pulmonary amebiasis without either a liver abscess or amebic colitis must be distinguished from bacterial abscesses and neoplastic disease. A sputum cytologic examination combined with PCR for DNA extracted from a sputum sample is a good approach to the diagnosis of a pulmonary amebic abscess.     

On the pathogenicity of Entamoeba histolytica. Part I: The role of bacterial associate on the modification of virulence of E. histolytica.

Of the 3 strains of Escherichia coli used, only Milner A strain was found capable of modifying the virulence of Entamoeba histolytica. None out of twenty-four hamsters inoculated with either 5 X 10(5) of axenically-cultured E. histolytica of NIH: 200 strain, or 1 X 10(7) of Esch. coli (A, B or C strains), was found to have amebic liver abscess. Whereas one out of six hamsters inoculated with the same number of amebae preincubated for 12 hrs with Esch. coli of Milner A strain was found to have abscess. The role of bacterial associate seems to be nothing but provides a more suitable environment for amebae, thus enable them to survive longer and endow them more time to adapt themselves to the given new environment. From liver abscess E. histolytica was recovered and successfully reaxenized. These amebae were capable of producing liver abscess, therefore the virulence seemed to be inheritable.     

Entamoeba histolytica: identification of a distinct beta2 integrin-like molecule with a potential role in cellular adherence

Entamoeba histolytica infection causes dysentery, intestinal colitis, and hepatic abscess in an estimated 50 million people worldwide. Attachment of E. histolytica trophozoites to intestinal epithelium and vascular endothelium during liver metastasis results in an inflammatory process. We report the identification of a distinct amebic beta2 integrin (CD18)-like molecule which affords adherence to TNF-alpha-activated endothelial cells. Data from flow cytometry and indirect immunofluorescence assays suggest the amebic beta2 integrin was localized to focal adhesion plates and was present in both E. histolytica and Entamoeba dispar. The amebic beta2 integrin appeared to be distinct from the amebic Gal/GalNAc lectin based on recombinant expression, amebic colocalization, and ELISA studies. Trophozoite adherence to endothelial cells expressing ICAM-1 (CD54) following activation with TNF-alpha or ICAM-1-transfected CHO cells was specifically inhibited with anti-CD18 or anti-CD54 MAbs. In summary, evidence in support of a distinct beta2 integrin-like molecule participating in amebic adherence to TNF-alpha-activated endothelial cells expressing ICAM-1 is presented. The presence of integrin-dependent binding may allow trophozoites to opportunistically adhere to activated intestinal epithelium or vascular endothelium expressing ICAM-1 during amebic colitis or hepatic abscess.     

Tissue invasion by Entamoeba histolytica: evidence of genetic selection and/or DNA reorganization events in organ tropism

Entamoeba histolytica infection may have various clinical manifestations. Nine out of ten E. histolytica infections remain asymptomatic, while the remainder become invasive and cause disease. The most common form of invasive infection is amebic diarrhea and colitis, whereas the most common extra-intestinal disease is amebic liver abscess. The underlying reasons for the different outcomes are unclear, but a recent study has shown that the parasite genotype is a contributor. To investigate this link further we have examined the genotypes of E. histolytica in stool- and liver abscess-derived samples from the same patients. Analysis of all 18 paired samples (16 from Bangladesh, one from the United States of America, and one from Italy) revealed that the intestinal and liver abscess amebae are genetically distinct. The results suggest either that E. histolytica subpopulations in the same infection show varying organ tropism, or that a DNA reorganization event takes place prior to or during metastasis from intestine to liver.     

Entamoeba histolytica phagocytosis of human erythrocytes involves PATMK, a member of the transmembrane kinase family

Entamoeba histolytica is the cause of amebic colitis and liver abscess. This parasite induces apoptosis in host cells and utilizes exposed ligands such as phosphatidylserine to ingest the apoptotic corpses and invade deeper into host tissue. The purpose of this work was to identify amebic proteins involved in the recognition and ingestion of dead cells. A member of the transmembrane kinase family, phagosome-associated TMK96 (PATMK), was identified in a proteomic screen for early phagosomal proteins. Anti-peptide affinity-purified antibody produced against PATMK demonstrated that it was a type I integral membrane protein that was expressed on the trophozoite surface, and that co-localized with human erythrocytes at the site of contact. The role of PATMK in erythrophagocytosis in vitro was demonstrated by: (i) incubation of ameba with anti-PATMK antibodies; (ii) PATMK mRNA knock-down using a novel shRNA expression system; and (iii) expression of a carboxy-truncation of PATMK (PATMK(delta932)). Expression of the carboxy-truncation of PATMK(delta932) also caused a specific reduction in the ability of E. histolytica to establish infection in the intestinal model of amebiasis, however these amebae retained the ability to cause hepatic abscesses when directly injected in the liver. In conclusion, PATMK was identified as a member of the TMK family that participates in erythrophagocytosis and is uniquely required for intestinal infection.     

Maintenance of integrity, viability, and adhesion of Entamoeba histolytica trophozoites in different incubation media

We have determined the integrity, viability and adhesion of Entamoeba histolytica HK9 and HM1 trophozoites during their incubation in two basal culture media (TP and TYI) and three saline media ("maintenance medium" MM-1 and two others buffered with HEPES). In basal culture media, more than 70% of the trophozoites maintained their integrity and adhesion to human red blood cells (RBC) for up to 4 h, and the proportion of those excluding Trypan blue decreased slowly after 2 h. In saline media, the number of ameba-RBC complexes reached a maximum after 20-30 min and then decreased rapidly (and fastest in MM-1), less than 10% of the amebae were intact after 3-4 h, and dye exclusion fell abruptly from the start of incubation. The number of ameba-RBC complexes formed and the rate of adhesion were highest in basal TP medium. Normal nonvacuolated refringent (NVR) trophozoites deteriorated progressively in all media--although much faster in the saline ones--to vacuolated refringent (VR), nonrefringent, and disrupted. Trypan blue was excluded by all NVR and a fraction of the VR trophozoites. Horse serum helped to maintain ameba integrity and viability, but inhibited adhesion in a concentration-dependent manner. We conclude that E. histolytica trophozoite integrity and adhesion are adequately preserved and should be characterized only in basal culture media, that refringence without vacuolization is a more stringent characteristic of ameba quality than Trypan blue exclusion, and that some serum component inhibits ameba adhesion.     

Monoclonal antibodies directed against the galactose-binding lectin of Entamoeba histolytica enhance adherence.

The Entamoeba histolytica galactose-binding lectin is a surface glycoprotein composed of 170- and 35-kDa subunits. Inhibition of this lectin with galactose or anti-170 kDa subunit polyclonal antibody blocks amebic adherence to target cells and colonic mucin glycoproteins. We describe the properties of 10 mAb with specificity for the 170-kDa subunit. Based on competitive binding studies, six nonoverlapping antigenic determinants on the lectin were identified. The effect of the mAb on adherence of amebic trophozoites to both Chinese hamster ovary (CHO) cells and human colonic mucins was measured. Antilectin antibodies directed against epitopes 1 and 2 enhanced adherence, with the number of amebae having at least three adherent CHO cells increasing with the addition of epitope 1 mAb from 26 +/- 9 to 88 +/- 2% and the binding of colonic mucins increasing from 34 +/- 1 to 164 +/- 3 pg/10(5) amebae. Antibody-enhanced adherence remained 90 to 100% galactose inhibitable, occurred at 4 degrees C and was not Fc mediated. Univalent Fab fragments of epitope 1 mAb augmented mucin binding by 238% and CHO cell adherence by 338%. The binding of purified lectin to CHO cells was increased from 1.1 +/- 0.1 to 2.4 +/- 0.3 ng/10(3) CHO cells by mAb directed to epitope 1, demonstrating that enhanced adherence was due to direct activation of the lectin. mAb to epitope 3 bound to the lectin only upon its solubilization from the membrane and had no effect on adherence. Adherence to CHO cells and mucins was inhibited from 50 to 75% by mAb to epitopes 4 and 5; epitope 6 mAb inhibited amebic adherence to CHO cells but not mucins. The pooled sera from 10 patients with amebic liver abscess blocked the binding to the 170-kDa subunit of mAb directed to all six epitopes. Striking individual variations in the effects of immune sera on adherence were observed. Although the sera of all 44 South African patients with amebic liver abscess had high titer anti-lectin antibodies, 16 patients' sera significantly (more than 3 SEM) enhanced adherence whereas 25 patients' sera significantly inhibited adherence. Antilectin antibodies exert profound functional effects on the interaction of E. histolytica with target cells and human colonic mucins. Exploration of the clinical consequences of adherence-enhancing and inhibitory antibody responses may give insight into the role of antilectin antibodies in immunity to invasive amebiasis.     

Antisense inhibition of amoebapore expression in Entamoeba histolytica causes a decrease in amoebic virulence

Amoebapores have been proposed to be a major pathogenicity factor of the protozoan parasite Entamoeba histolytica, which is responsible for the killing of target cells. These 77-residue peptides are structural and functional analogues of NK-lysin and granulysin of porcine and human cytotoxic lymphocytes. Inhibition of amoebapore gene expression in amoebae was obtained following transfection with a hybrid plasmid construct (pAP-R2) containing the Neo resistance gene and the gene coding for amoebapore A, including its 5' and 3' untranslated region (UTR) sequences, in reverse orientation under a promoter (g34) taken from one of the E. histolytica ribosomal protein (RP-L21) gene copies. Transfectants of virulent E. histolytica strain HM-1:IMSS, in which the expression of amoebapore was inhibited by approximately 60%, were significantly less pathogenic. Cytopathic and cytolytic activities of viable trophozoites against mammalian nucleated cells, as well as lysis of red blood cells, were markedly inhibited. Moreover, trophozoite extracts of pAP-R2 transfectant displayed lower pore-forming activity and were less potent in inhibiting bacterial growth compared with controls. Notably, liver abscess formation in hamsters by the pAP-R2 transfectant was substantially impaired. These results demonstrate for the first time that amoebapore is one of the pathogenicity factors by which trophozoites of E. histolytica exert their remarkable cytolytic and tissue destructive activity.     

Cyclosporin A inhibits calcineurin (phosphatase 2B) and P-glycoprotein activity in Entamoeba histolytica

Cyclosporin A (CsA) inhibits the proliferation of several protozoan parasites through blocking the activity of calcineurin (Cn) or P-glycoproteins (Pgp). We report here, that inhibition of the proliferation of Entamoeba histolytica trophozoites, the causal agent of human amebiasis, is due to interference of the phosphatase activity of Cn, in a similar fashion to the effect of this immunosuppressive drug on T lymphocytes. The non-immunosuppressive CsA analog PSC-833, which binds Pgp without interfering the function of Cn, did not inhibit the proliferation of HM1:IMSS trophozoites. Moreover, phosphatase activity of amebic Cn, detected using the phosphopeptide RII, was drastically affected by incubation with CsA, but not with PSC-833. On the other hand, both drugs were also tested on clone C2 trophozoites, which grow in the presence of emetine due to over-expression of Pgp. The effect of CsA was similar to that observed on HM1:IMSS trophozoites, whereas PSC-833 only affected the proliferation and viability of clone C2 when the trophozoites were grown in the presence of 40 microM of emetine, suggesting an interference of the Pgp activity. This suggestion was confirmed by results from experiments of Pgp-dependent effux of rhodamine from pre-loaded trophozoites, in the presence of either of these drugs. Therefore, CsA inhibition of E. histolytica trophozoite proliferation is more likely due to Cn than Pgp activity inhibition.     

Comparative proteomic analysis of two Entamoeba histolytica strains with different virulence phenotypes identifies peroxiredoxin as an important component of amoebic virulence

Entamoeba histolytica is a protozoan intestinal parasite that causes amoebic colitis and amoebic liver abscess. To identify virulence factors of E. histolytica, we first defined the phenotypes of two E. histolytica strains, HM-1:IMSS, the prototype virulent strain, and E. histolytica Rahman, a strain that was reportedly less virulent than HM-1:IMSS. We found that compared with HM-1:IMSS, Rahman has a defect in erythrophagocytosis and the ability to cause amoebic colitis in human colonic xenografts. We used differential in-gel 2D electrophoresis to compare the proteome of Rahman and HM-1:IMSS, and identified six proteins that were differentially expressed above a fivefold level between the two organisms. These included two proteins with antioxidative properties (peroxiredoxin and superoxide dismutase), and three proteins of unknown function, grainin 1, grainin 2 and a protein containing a LIM-domain. Overexpression of peroxiredoxin in Rahman rendered the transgenic trophozoites more resistant to killing by H2O2 in vitro, and infection with Rahman trophozoites expressing higher levels of peroxiredoxin was associated with higher levels of intestinal inflammation in human colonic xenografts, and more severe disease based on histology. In contrast, higher levels of grainin appear to be associated with a reduced virulence phenotype, and E. histolytica HM-1:IMSS trophozoites infecting human intestinal xenografts show marked decreases in grainin expression. Our data indicate that there are definable molecular differences between Rahman and HM-1:IMSS that may explain the phenotypic differences, and identify peroxiredoxin as an important component of virulence in amoebic colitis.     

Recognition of 29 kDa surface-associated adhesive molecule of Entamoeba histolytica by monoclonal antibodies

Monoclonal antibodies have been developed and used as specific probe to locate and identify a 29-kDa molecule of axenic Entamoeba histolytica trophozoites. Monoclonal antibody produced by clone C8 (MoAb C8) strongly agglutinated the amoebic trophozoites. The immunofluorescence of live E. histolytica trophozoites and surface fluorescence of acetone-fixed trophozoites by MoAb C8 indicated existence of a 29-kDa molecule on surface-associated plasma membrane of E. histolytica. The monoclonal antibody belonged to IgG1 isotype. The prior treatment of E. histolytica trophozoites with MoAb C8 resulted in significant (P less than 0.01) reduction in adherence of amoebic trophozoites to cultured Chinese Hamster Ovary cells and significant (P less than 0.01) reduction in cytotoxicity to cultured Baby Hamster Kidney cells. Pretreatment of amoebic trophozoites with MoAb C8 prior to cultivation in TPS-1 medium resulted in significant (P less than 0.01) reduction in growth of the parasite. Thus, the data suggested that the surface-exposed 29-kDa molecule may be one of the receptors involved in E. histolytica host cell interactions and may possibly modulate amoebic disease processes.     

1,25-Dihydroxyvitamin D3 enhancement of concanavalin-A induced bovine lymphocyte proliferation: requirement of monocytes

The effect of 1,25-(OH)2D3 on Concanavalin-A (ConA) mediated bovine lymphocyte proliferation was dependent on the magnitude of the proliferative response. Lymphocytes from cows with high inherent proliferative responses (134,904 +/- 15,488 cpm/well) were unaffected by 1,25-(OH)2D3; whereas, lymphocytes from cows with low inherent proliferative responses (46,317 +/- 6000 cpm/well) were stimulated 75% (P less than 0.01) by 10(-10)M 1,25-(OH)2D3. At low initial proliferation rates, seen with low density cultures enriched for lymphocytes, the effect of 1,25-(OH)2D3 on proliferation changed from inhibition in the absence of added monocytes to stimulation at 18-23% monocyte addition. These results suggest that 1,25-(OH)2D3 possesses both stimulatory and inhibitory effects on ConA-induced proliferation that are monocyte dependent.     

Interaction between pathogenic amebas and fibronectin: substrate degradation and changes in cytoskeleton organization

Invasion of human tissues by the parasitic protozoan Entamoeba histolytica is a multistep process involving, as a first step, the recognition of surface molecules on target tissues by the amebas or trophozoites. This initial contact is followed by the release of proteolytic and other activities that lyse target cells and degrade the extracellular matrix. In other parasitic diseases, as well as in certain cancers, the interaction of invasive organisms or cells with fibronectin (FN) through specific receptors has been shown to be the initial step in target cell recognition. Interaction with FN triggers the release of proteolytic activities necessary for the effector cell migration and invasion. Here, we describe the specific interaction of Entamoeba histolytica trophozoites with FN, and identify a 37-kD membrane peptide as the putative receptor for FN. The interaction between the parasite and FN leads to a response reaction that includes the secretion of proteases that degrade the bound FN and the rearrangement of amebic actin into "adhesion plates" at sites of contact with FN-coated surfaces. The kinetics of the interaction was determined by measuring the binding of soluble 125I-FN to the trophozoites and visualization of the bound protein using specific antibodies. Degradation of FN was measured by gel electrophoresis and the release of radioactivity into the incubation medium. Focal degradation of FN was visualized as black spots under the trophozoites at contact sites with fluorescent FN. We conclude that the interaction of E. histolytica with FN occurs through a specific surface receptor. The interaction promotes amebic cytoskeleton changes and release of proteases from the parasite. The binding and degradation of extracellular matrix components may facilitate the migration and penetration of amebas into tissues, causing the lesions seen in human hosts.     

Sphingosine-1-phosphate receptor agonists suppress concanavalin A-induced hepatic injury in mice

T cell-mediated immune responses play a critical role in a variety of liver injuries including autoimmune hepatitis. Injection of concanavalin A (Con A) into mice mimics the histological and pathological phenotype of T cell-mediated hepatitis. Recent advances in host immune control of organ transplantation include the development of sphingosine-1-phosphate (S1P) receptor agonists such as FTY720, which alter lymphocyte homing but do not suppress host general immunity. Herein we examined the effect of the new S1P receptor agonist KRP-203 on the Con A-induced liver damage model. In normal liver lymphocytes of BALB/c mice, both FTY720 and KRP203 promoted lymphocyte sequestering from the liver to secondary lymph nodes and significantly reduced the number of liver lymphocytes (p<0.05). Based on this observation, KRP203 was employed in the Con A-induced hepatitis model. KRP203 markedly reduced the number of CD4(+) lymphocytes that infiltrate Con A-treated liver (p<0.05) and successfully reduced serum transaminase elevation (p=0.017), therefore protecting mice from Con A-induced liver injury. Interestingly this homing modulation less occurs in natural hepatic T cell homing through the chemokine receptor, CXCR4. Therefore, S1P receptor agonists preferentially target CXCR4(+)CD4(+) peripheral blood T lymphocytes and suppress the occurrence of Con A-induced hepatitis, suggesting their therapeutic usefulness against T cell-mediated hepatic injury.