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Essential Role of Extrathymic T Cells in Protection Against Malaria¹

Department of Immunology, Niigata University School of Medicine, Niigata, Japan

	Abstract

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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 10³ 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-2R⁺TCR⁺). Unconventional CD8⁺ NKT cells (V14^-) 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.

	Introduction

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Many investigators still believe that conventional T and B cells are associated with protection against malaria. Therefore, several Ags that are expressed by Plasmodium are used for immunization against malaria (1, 2, 3, 4, 5, 6). These trials examined the concept of the induction of anti-malaria Abs produced by conventional B cells and the induction of cellular immunity mediated by conventional T cells. This concept arises from earlier reports that CD4⁺ (7, 8, 9, 10, 11, 12, 13) or CD8⁺ (14) T cells are associated with protection against malaria. However, all these studies were performed before introduction of the concept of extrathymic T cells.

In a series of recent studies, we and other investigators have reported that extrathymic T cells are present in the digestive tract in such organs as the liver (15, 16, 17, 18) and intestine (19, 20, 21, 22, 23) and that these T cells comprise an innate immune system in conjunction with autoantibody-producing B-1 cells. When we observed immunoparameters in mice infected with Plasmodium, there was no evidence of the activation of conventional T cells (i.e., TCR^high cells) (24, 25). Rather, these mice showed thymic atrophy during malarial infection, suggesting the arrest of conventional T cell differentiation. Inversely, primordial T cells (i.e., TCR^int cells) were highly activated in number and function, especially in the liver and spleen, and the sera always contained autoantibodies.

Primordial T cells include the NK1.1⁺TCR^int subset (i.e., NKT cells) and the NK1.1^-TCR^int subset (17). NKT cells are primarily derived from the thymus (through an alternative intrathymic pathway but not the mainstream of the intrathymic pathway) and home to the liver (26, 27, 28), whereas NK1.1^-TCR^int cells are truly of extrathymic origin (29). Almost all T cells that are identified in athymic nude mice are NK1.1^-TCR^int cells.

In light of these findings, we further characterized the properties of T cells in athymic nude mice with malarial infection. If protection against malaria is achieved as the result of innate immunity as we propose, athymic mice should survive malarial infection due to the action of extrathymic T cells and B-1 cells. This possibility was investigated in the present study.

	Materials and Methods

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Mice and parasites

C57BL/6 (B6) and B6-nu/nu mice at the age of 8–15 wk were used. The mice were maintained at the animal facility of Niigata University (Niigata, Japan) under specific pathogen-free conditions. Plasmodium yoelii 17XNL (nonlethal strain), a generous gift of Dr. S. Waki (Gunma Prefectural College of Health Science, Maebashi, Japan), was used (24). Parasites were maintained by routine in vivo passages in mice. Mice were infected by an i.p. injection of 10⁴ or 5 x 10³ parasitized erythrocytes per mouse. Parasitemia in the blood was observed by Giemsa staining every 2 or 3 days and the mice were sacrificed at the indicated days after infection. Lymphocytes were obtained from the liver, spleen, and thymus (in the case of euthymic mice) in control and infected mice.

Cell preparation

Hepatic mononuclear cells (MNC)³ were isolated by a previously described method (25). Briefly, the liver was removed, pressed through 200-gauge stainless steel mesh, and suspended in Eagle’s MEM (Nissui Pharmaceutical, Tokyo, Japan) supplemented with 5 mM HEPES and 2% heat-inactivated newborn calf serum. After being washed once with medium, the cells were fractionated by centrifugation in 15 ml of 35% Percoll solution (Amersham Pharmacia Biotech, Piscataway, NJ) for 15 min at 2000 rpm. The pellet was resuspended in erythrocyte lysing solution (155 mM NH₄Cl, 10 mM KHCO₃, 1 mM EDTA-Na, and 170 mM Tris (pH 7.3)). Splenocytes and thymocytes were obtained by forcing the spleen and thymus through stainless steel mesh. Splenocytes were used after erythrocyte lysing.

Immunofluorescence test

FITC-, PE-, or biotin-conjugated reagents of mAbs were used and biotin-conjugated reagents were developed with tricolor-conjugated streptavidin (Caltag Laboratories, San Francisco, CA) (30). The mAbs used here were anti-CD3 (145-2C11), anti-IL-2R (TM-1), anti-NK1.1 (PK136), anti-CD4 (RM4-5), anti-CD8 (53-6.7), anti-TCR (H57-597), anti-TCR (GL3), and anti-erythrocyte (TER119) mAbs (BD PharMingen, San Diego, CA). Cells were analyzed by FACScan (BD Biosciences, Mountain View, CA). To prevent nonspecific binding of mAbs, CD16/32 (2.4G2; BD PharMingen) was added before staining with labeled mAb. Dead cells were excluded by forward scatter, side scatter, and propidium iodide gating.

RT-PCR for V14 mRNA

Total RNA was extracted from MNC by the acid guanidium thiocyanate-phenol-chloroform method. cDNA was synthesized using Moloney leukemia virus transcriptase (Takara, Tokyo, Japan) and random hexamer primer (Takara). PCR amplification of synthesized cDNA was conducted as previously described (24). PCR products as well as markers were estimated by staining with ethidium bromide. A control experiment was done by using G3PDH mRNA.

Histology

Tissues were fixed in 10% phosphate-buffered formalin and embedded in paraffin. Sections 4 µm in thickness were stained with H&E.

Serum levels of anti-DNA Ab

Measurements of IgG and IgM Abs reacting with ssDNA by the ELISA method were modified as previously described (31). Standard sera were obtained from MRL-lpr/lpr (lpr) mice (after the onset of disease) and arbitrarily determined to contain 100 U of anti-DNA Ab. In each test, the titer was expressed as the percentage in comparison with the standard sera.

Cell transfer experiments

Liver MNC that were isolated from mice with or without malarial infection were used for cell transfer experiments (32). A total of 5 x 10⁶ liver MNC were i.v. injected into 4-Gy-irradiated B6 or B6-nu/nu mice. These mice were infected with malaria within 1 day after cell transfer.

	Results

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Survival conditions for athymic nude mice infected with malaria

Control B6 mice were able to recover from malarial infection when 10⁴ P. yoelii-infected erythrocytes (per mouse) were injected (Fig. 1A). However, the same injection resulted in death in athymic nude mice, which showed severe parasitemia in the blood (up to 60% parasitemia). Therefore, we reduced the number of infected erythrocytes to 5 x 10³ per mouse. Although the parasitemia continued longer in athymic mice than in B6 mice, athymic mice finally recovered from malarial infection. Under the above conditions of application, immunologic responses seen in athymic nude mice were investigated thereafter.

View larger version (31K): [in this window] [in a new window]   FIGURE 1. Parasitemia and immunoparameters in control B6 mice and athymic nude mice after malarial infection. A, Parasitemia and death. B, Time kinetics of the number of lymphocytes and lymphocyte subsets in the liver (or the spleen). C, Proportional changes of NK1.1+TCRint and NK1.1-TCRint cells among total TCRint cells in the liver during malarial infection. Malaria-infected erythrocytes (104 or 5 x 103) were injected into B6 mice and athymic nude mice. In the case of B6 mice, the mean and 1 SD were produced from four mice. NK1.1+CD3int (IL-2R+) and NK1.1-CD3int (IL-2R+) subsets were identified by two-color staining for NK1.1 and CD3. All these subsets were IL-2R+ (see the subsequent phenotypic study). The mean and 1 SD were produced from four mice.

As was the case in a previous study (24), the major organs where lymphocytes expanded during malarial infection were the liver and spleen. We then compared the pattern of variation in the number of lymphocytes in the liver and spleen between control B6 mice and athymic mice (Fig. 1B). Severe lymphocytosis was seen in the liver and spleen of both B6 mice and athymic mice after malarial infection (5 x 10³ P. yoelii-infected erythrocytes per mouse). The onset of lymphocytosis tended to be retarded in athymic mice, but the maximum number on day 21 was greater in athymic mice than in B6 mice.

Because the major lymphocyte subsets that expanded during malarial infection were NK1.1⁺CD3^int and NK1.1^-CD3^int cells in B6 mice, the time kinetics of these subsets were also identified (Fig. 1C). Two-color staining of lymphocytes for CD3 and NK1.1 was conducted in the liver of both B6 and athymic mice in this experiment. In both types of mice, the major expanding subset was NK1.1^-CD3^int cells. This was more striking in the athymic nude mice.

Details of the phenotypic characterization of lymphocytes that expanded in the liver and spleen during malarial infection

Two-color staining for CD3 and IL-2R is represented first (Fig. 2A). This staining simultaneously identified IL-2R⁺CD3^- NK cells, IL-2R⁺CD3^int cells, and IL-2R^-CD3^high conventional T cells, especially in the liver and spleen of normal B6 mice (see Fig. 2A, left column). However, this general staining pattern was prominently changed in B6 mice after malarial infection. IL-2R⁺CD3^int cells became a major lymphocyte subset in both the liver and spleen (Fig. 2A, arrowheads in the liver). Because the intensity of IL-2R expression decreased slightly in CD3^int cells, the area of CD3^int cells spread to that of IL-2R^-CD3^high cells. In the case of athymic nude mice, IL-2R⁺CD3^- NK cells were abundant in the liver, and T cells that existed in the liver and spleen were only IL-2R⁺CD3^int cells. During malarial infection, the proportion of NK cells decreased while that of CD3^int cells increased in the liver (Fig. 2A, arrowhead on day 21) and in the spleen.

View larger version (69K): [in this window] [in a new window]   FIGURE 2. Phenotypic characterization of lymphocytes in the liver and spleen of B6 mice and athymic nude mice. A, Two-color staining for CD3 and IL-2R. B, Two-color staining for NK1.1 and other markers. C, Two-color staining for TER119 and CD3. Lymphocytes were isolated at days 10 and 21 after malarial infection. Numbers represent the percentage of fluorescence-positive cells in the corresponding areas. The data shown are representative of three experiments. The expansion of IL-2R+CD3int cells and NK1.1+ T cells is indicated by arrowheads.

In the case of athymic mice, NKT cells, which are primarily of thymic origin, were extremely few before malarial infection. However, NKT cells expanded in the liver of athymic mice (Fig. 2B, arrowhead on day 21). Two-color stainings for other combinations revealed that these NKT cells were CD8⁺TCR^int or CD8⁺TCR⁺. CD4⁺ NKT cells never appeared in conjunction with malarial infection in nude mice.

During malarial studies in humans and mice, we have often observed clusters of cells in the parenchymal space of the liver; such clusters contain not only lymphoid cells but also erythroid cells. In this regard, we conducted erythrocyte (TER119⁺) staining by using liver MNC (Fig. 2C). These liver MNC were used after RBC lysis; therefore, denucleated RBC were not present in these preparations. Irrespective of whether the mice were euthymic or athymic, nucleated TER119⁺ erythrocytes newly appeared after malarial infection (day 21). It was speculated that extramedullary erythropoiesis began in the liver as the result of malarial infection.

No appearance of V14J281⁺ NKT cells before and after malarial infection in athymic mice

Phenotypic study showed that CD4⁺ NKT cells did not appear in athymic nude mice even after malarial infection. This result was confirmed by RT-PCR method using V14J281 mRNA (Fig. 3). Thus, conventional CD4⁺ NKT cells preferentially use an invariant chain of V14J281 gene for TCR (17). The sign of V14 mRNA was detected in liver lymphocytes of euthymic B6 mice and this sign was almost unchanged in these mice after malarial infection. However, irrespective of malarial infection, the sign of V14 mRNA was not detected at all in liver lymphocytes of athymic nude mice.

View larger version (32K): [in this window] [in a new window]   FIGURE 3. No expansion of V14J281+ NKT cells during malarial infection. To confirm that CD4+ NKT cells did not expand after malarial infection, RT-PCR method was applied to detect V14J281 mRNA. Total RNA was extracted from liver lymphocytes of B6 and B6-nu/nu mice before (Cont.) and after the infection (days 7, 14, and 21).

The expansion of NK1.1^-TCR^int cells and nucleated erythrocytes in the liver after malarial infection suggested a new generation of these cells in the liver. This possibility was examined by histology (Fig. 4). There were no clusters in the liver of athymic mice without malarial infection (Fig. 4A). In sharp contrast, large cell clusters appeared in the parenchymal space of the liver in both euthymic mice (Fig. 4B) and athymic mice (Fig. 4C) after malarial infection (day 21).

View larger version (52K): [in this window] [in a new window]   FIGURE 4. Histology of the liver in light microscopy (x400). A, The liver of normal B6 athymic mice. B, The liver of B6 mice after malarial infection (day 21). C, The liver of B6 athymic mice after malarial infection (day 21). H&E staining was conducted.

There was intimate cooperation between extrathymic T cells and B-1 cells in certain autoimmune diseases and during malarial infection (25). This possibility was examined in athymic nude mice infected with malaria (Fig. 5). B6 mice infected with malaria were examined in parallel. In the case of B6 mice, both IgG and IgM types of autoantibodies against denatured DNA were detected. However, only the IgM type of autoantibodies was detected in athymic mice after malarial infection. In these experiments, sera of lpr mice were used as a positive control (adjusted to 100 U/ml).

View larger version (31K): [in this window] [in a new window]   FIGURE 5. Autoantibody production in B6 mice and athymic nude mice after malarial infection. Sera were obtained at the indicated points of time. Both IgG and IgM types of autoantibodies against denatured DNA were detected by ELISA. Sera of lpr mice (after the onset of autoimmune disease) were used as a positive control (adjusted as 100 U/ml). The mean and 1 SD were produced by four experiments.

To directly prove the capability of protection against malaria by extrathymic T cells, cell transfer experiments of liver MNC isolated from athymic nude mice with or without malarial infection were conducted (Fig. 6). B6 mice and athymic mice were used as recipients after 4-Gy irradiation. Transferred cells were prepared from normal athymic nude mice or from athymic nude mice that had recovered from malaria (within 4 mo after recovery). When 4-Gy-irradiated B6 mice and 4-Gy-irradiated athymic mice (no cell transfer) were infected with malaria, all of these mice died as a consequence of parasitemia. This was also the case when naive MNC (5 x 10⁶ per mouse) were transferred into these mice (Fig. 6, lower panels). In sharp contrast, when immune MNC (5 x 10⁶ per mouse) were transferred into these mice, both B6 and athymic mice were able to survive and showed no parasitemia. In other words, only liver lymphocytes isolated from athymic mice that had recovered from malaria were able to protect mice from malaria.

View larger version (41K): [in this window] [in a new window]   FIGURE 6. Protection against malaria as shown by cell transfer experiments using liver MNC isolated from athymic mice recovered from malaria. Normal B6 mice and athymic nude mice were used as controls. Irradiated (4 Gy) B6 mice and athymic nude mice were also used. These irradiated mice were also used as recipients for cell transfer experiments. In the case of control B6 mice, the mean and 1 SD were produced from four mice. Liver MNC were isolated from normal athymic mice and athymic mice that had recovered from malaria (within 4 mo of the recovery). A total of 5 x 106 liver MNC per mouse were injected into recipient mice.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

For a long time, protection against malaria has been considered to be due to immunological events mediated by conventional T cells, including CD4⁺ and CD8⁺ T lymphocytes (7, 8, 9, 10, 11, 12, 13, 14). However, this conception raises several questions: 1) why does immunological memory that humans or animals once acquired by malarial infection disappear 1 year or more after the infection (24, 33, 34), 2) why do autoantibodies often appear during malarial infection (35, 36, 37, 38, 39), and 3) why is thymic atrophy always accompanied by malarial infection (25)? The third question is serious. If conventional T cells are important for protection against malaria, the arrest of intrathymic T cell differentiation by severe thymic atrophy during malarial infection is not easily explained.

According to the above-mentioned reasons, we conducted experiments of malarial infection in athymic nude mice that carry only extrathymic T cells (29). Under athymic conditions, these mice primarily lack two important T lymphocyte subsets of thymic origin, namely, conventional T cells (i.e., NK1.1^-IL-2R^-TCR^high cells) and NKT cells (i.e., NK1.1⁺IL-2R⁺TCR^int cells). Although NKT cells are abundant in the liver of euthymic mice, these primordial T cells or their precursors originate in the thymus through an alternative intrathymic pathway (27, 28). Indeed, as shown in the present study, athymic nude mice carry only extrathymic T cells (i.e., NK1.1^-IL-2R⁺TCR^int cells). In this situation, we found that extrathymic T cells had the ability to protect mice from malarial infection.

In this study, we used 5 x 10³ P. yoelii-infected erythrocytes to induce the blood stage malarial infection. This was due to the fact that athymic nude mice were more sensitive to malarial death than euthymic mice with the same genetic background (B6). We have to consider the possibility that some other lymphocyte subsets may cooperatively act with extrathymic T cells for malarial protection. In this case, one of the candidates is NKT cells. Under euthymic conditions, we have reported that NKT cells were also activated during malarial infection and that NKT-deficient mice (e.g., CD1d knockout mice) were more susceptible to malarial death than normal mice (25).

Extrathymic T cells carry many properties as primordial T cells (15, 16, 17, 18); one such property is that the activation of extrathymic T cells is often accompanied by autoantibody production by primordial B-1 cells (25). When syngeneic denatured liver tissue was injected into mice, mice fell victim to autoimmune hepatitis. At this time, thymic atrophy, the activation of extrathymic T cells, and autoantibodies against denatured DNA were simultaneously induced (our unpublished observation). Chronic graft-vs-host disease is also known as an autoimmune-like state that accompanies thymic atrophy, the activation of extrathymic T cells, and autoantibody production (40, 41). Under both euthymic conditions and athymic conditions (the present study), a similar phenomenon (activation of extrathymic T cells and autoantibody production) was evoked during malarial infection.

Primarily, CD4⁺ NKT cells that use V14J281 are absent in athymic nude mice (42, 43, 44, 45). Even after malarial infection, such CD4⁺ NKT cells did not appear in these mice. However, it was found that a significant proportion of NKT cells did newly appear in the liver of athymic mice after malarial infection. All of these NKT cells were CD8⁺ or DN cells that use TCR or TCR. None of them used an invariant chain of V14J281 as shown by the RT-RCR method. Another interesting finding was the new appearance of TER119⁺ nucleated erythrocytes in the liver after malarial infection. This was seen in both euthymic and athymic mice. It is conceivable that the large cell clusters in the parenchymal space of the liver (see Fig. 4) may comprise not only newly generated extrathymic T cells but also newly generated erythrocytes (i.e., extramedullary erythropoiesis).

In the case of athymic mice, only the IgM type (but not IgG type) of autoantibodies against denatured DNA appeared after malarial infection. In contrast, autoimmune MRL-lpr/lpr mice and euthymic mice with malaria produced both types of the autoantibodies. It is speculated that some help (e.g., by conventional T cells) may be required for the complete production of autoantibodies.

In a final cell transfer experiment, we demonstrated that extrathymic T cells had the ability to protect mice from malarial death. Namely, when extrathymic T cells were isolated from the liver of athymic nude mice that had recovered from malarial infection, these T cells rescued both 4-Gy-irradiated euthymic and athymic mice from death. In conjunction with the expansion of limited lymphocyte subsets (i.e., extrathymic T cells and possible B-1 cells) during malarial infection, it is presumed that the protection against malaria may be the result of immunological events mediated by the innate immune system rather than by the developed immune system (mediated by conventional T and B cells).

	Acknowledgments

 
We thank Yuko Kaneko for preparation of the manuscript.

	Footnotes

 
¹ This study was supported by grants in-aid for scientific research from the Ministry of Education, Science and Culture, Japan.

² Address correspondence and reprint requests to Dr. Toru Abo, Department of Immunology, Niigata University School of Medicine, Asahimachi-dori 1-757, Niigata 951-8510, Japan. E-mail address: immunol2{at}med.niigata-u.ac.jp

³ Abbreviation used in this paper: MNC, mononuclear cell.

Received for publication February 21, 2002. Accepted for publication April 16, 2002.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Playfair, J. H., J. B. De Souza, R. R. Freeman, A. A. Holder. 1985. Vaccination with a purified blood-stage malaria antigen in mice: correlation of protection with T cell mediated immunity. Clin. Exp. Immunol. 62:19.[Medline]
2. Dick, S., M. Waterfall, J. Currie, A. Maddy, E. Riley. 1996. Naive human T cells respond to membrane-associated components of malaria-infected erythrocytes by proliferation and production of interferon-. Immunology 88:412.[Medline]
3. De Souza, J. B., J. H. Playfair. 1995. A novel adjuvant for use with a blood-stage malaria vaccine. Vaccine 13:1316.[Medline]
4. Miyahira, Y., A. Garcia-Sastre, D. Rodriguez, J. R. Rodriguez, K. Murata, M. Tsuji, P. Palese, M. Esteban, F. Zavala, R. S. Nussenzweig. 1998. Recombinant viruses expressing a human malaria antigen can elicit potentially protective immune CD8⁺ responses in mice. Proc. Natl. Acad. Sci. USA 95:3954.[Abstract/Free Full Text]
5. Chen, Q., A. Heddini, A. Barragan, V. Fernandez, S. F. A. Pearce, M. Wahlgren. 2000. The semiconserved head structure of Plasmodium falciparum erythrocyte membrane protein 1 mediates binding to multiple independent host receptors. J. Exp. Med. 192:1.[Abstract/Free Full Text]
6. Bruna-Romero, O., G. Gonzalez-Aseguinolaza, J. C. R. Hafalla, M. Tsuji, R. S. Nussenzweig. 2001. Complete, long-lasting protection against malaria of mice primed and boosted with two distinct viral vectors expressing the same plasmodial antigen. Proc. Natl. Acad. Sci. USA 98:11491.[Abstract/Free Full Text]
7. Langhorne, J.. 1989. The role of CD4⁺ T-cells in the immune response to Plasmodium chabaudi. Parasitol. Today 5:362.
8. Weiss, W. R., M. Sedegah, J. A. Berzofsky, S. L. Hoffman. 1993. The role of CD4⁺ T cells in immunity to malaria sporozoites. J. Immunol. 151:2690.[Abstract]
9. Phillips, R. S., K. E. Mathers, A. W. Taylor-Robinson. 1994. T cells in immunity to Plasmodium chabaudi chabaudi: operation and regulation of different pathways of protection. Res. Immunol. 145:406.[Medline]
10. Taylor-Robinson, A. W.. 1995. Regulation of immunity to malaria: valuable lessons learned from murine models. Parasitol. Today 11:334.[Medline]
11. Currier, J., H. P. Beck, B. Currie, M. F. Good. 1995. Antigens released at schizont burst stimulate Plasmodium falciparum-specific CD4⁺ T cells from non-exposed donors: potential for cross-reactive memory T cells to cause disease. Int. Immunol. 7:821.[Abstract/Free Full Text]
12. Charoenvit, Y., V. F. Majam, G. Corradin, Jr J. B. Sacci, R. Wang, D. L. Doolan, T. R. Jones, E. Abot, M. E. Patarroyo, F. Guzman, S. L. Hoffman. 1999. CD4⁺ T-cells- and interferon-dependent protection against murine malaria by immunization with linear synthetic peptides from a Plasmodium yoelii 17-kilodalton hepatocyte erythrocyte protein. Infect. Immun. 67:5604.[Abstract/Free Full Text]
13. Schlotmann, T., I. Waase, C. Jülch, U. Klauenberg, B. Müller-Myhsok, M. Dietrich, B. Fleischer, B. M. Bröker. 2000. CD4 T lymphocytes express high levels of the T lymphocyte antigen CTLA-4 (CD152) in acute malaria. J. Infect. Dis. 182:367.[Medline]
14. Doolan, D. L., S. L. Hoffman. 1999. IL-12 and NK cells are required for antigen-specific adaptive immunity against malaria initiated by CD8⁺ T cells in the Plasmodium yoelii model. J. Immunol. 163:884.[Abstract/Free Full Text]
15. Abo, T., T. Ohteki, S. Seki, N. Koyamada, Y. Yoshikai, T. Masuda, H. Rikiishi, K. Kumagai. 1991. The appearance of T cells bearing self-reactive T cell receptor in the livers of mice injected with bacteria. J. Exp. Med. 174:417.[Abstract/Free Full Text]
16. Sato, K., K. Ohtsuka, K. Hasegawa, S. Yamagiwa, H. Watanabe, H. Asakura, T. Abo. 1995. Evidence for extrathymic generation of intermediate TCR cells in the liver revealed in thymectomized, irradiated mice subjected to bone marrow transplantation. J. Exp. Med. 182:759.[Abstract/Free Full Text]
17. Watanabe, H., C. Miyaji, Y. Kawachi, T. Iiai, K. Ohtsuka, T. Iwanaga, H. Takahashi-Iwanaga, T. Abo. 1995. Relationships between intermediate TCR cells and NK1.1⁺ T cells in various immune organs: NK1.1⁺ T cells are present within a population of intermediate TCR cells. J. Immunol. 155:2972.[Abstract]
18. Watanabe, H., C. Miyaji, S. Seki, T. Abo. 1996. c-kit⁺ stem cells and thymocyte precursors in the livers of adult mice. J. Exp. Med. 184:687.[Abstract/Free Full Text]
19. Ferguson, A., D. M. Parrott. 1972. The effect of antigen deprivation on thymus-dependent and thymus-independent lymphocytes in the small intestine of the mouse. Clin. Exp. Immunol. 12:477.[Medline]
20. Mosley, R. L., D. Styre, J. R. Klein. 1990. Differentiation and functional maturation of bone marrow-derived intestinal epithelial T cells expressing membrane T cell receptor in athymic radiation chimeras. J. Immunol. 145:1369.[Abstract]
21. Bandeira, A., S. Itohara, M. Bonneville, O. Burlen-Defranoux, T. Mota-Santos, A. Coutinho, S. Tonegawa. 1991. Extrathymic origin of intestinal intraepithelial lymphocytes bearing T-cell antigen receptor . Proc. Natl. Acad. Sci. USA 88:43.[Abstract/Free Full Text]
22. Rocha, B., P. Vassalli, D. Guy-Grand. 1991. The V repertoire of mouse gut homodimeric CD8⁺ intraepithelial T cell receptor /⁺ lymphocytes reveals a major extrathymic pathway of T cell differentiation. J. Exp. Med. 173:483.[Abstract/Free Full Text]
23. Kanamori, Y., K. Ishimaru, M. Nanno, K. Maki, K. Ikuta, H. Nariuchi, H. Ishikawa. 1996. Identification of novel lymphoid tissues in murine intestinal mucosa where clusters of c-kit⁺IL-7R⁺Thy1⁺ lympho-hemopoietic progenitors develop. J. Exp. Med. 184:1449.[Abstract/Free Full Text]
24. Weerasinghe, A., H. Sekikawa, H. Watanabe, M. K. Mannoor, S. R. M. Morshed, R. C. Halder, T. Kawamura, T. Kosaka, C. Miyaji, H. Kawamura, et al 2001. Association of intermediate T cell receptor cells, mainly their NK1.1^- subset, with protection from malaria. Cell. Immunol. 207:28.[Medline]
25. Mannoor, M. K., A. Weerasinghe, R. C. Halder, S. R. M. Morshed, A. Ariyashinghe, H. Watanabe, H. Sekikawa, T. Abo. 2001. Resistance to malarial infection is achieved by the cooperation of NK1.1⁺ and NK1.1^- subsets of intermediate TCR cells which are constituents of the innate immunity. Cell. Immunol. 211:96.[Medline]
26. Hammond, K., W. Cain, I. van Driel, D. Godfrey. 1998. Three day neonatal thymectomy selectively depletes NK1.1⁺ T cells. Int. Immunol. 10:1491.[Abstract/Free Full Text]
27. Tilloy, F., J. P. Di Santo, A. Bendelac, O. Lantz. 1999. Thymic dependence of invariant V14⁺ natural killer-T cell development. Eur. J. Immunol. 29:3313.[Medline]
28. Coles, M. C., D. H. Raulet. 2000. NK1.1⁺ T cells in the liver arise in the thymus and are selected by interactions with class I molecules on CD4⁺CD8⁺ cells. J. Immunol. 164:2412.[Abstract/Free Full Text]
29. Halder, R. C., T. Kawamura, M. Bannai, H. Watanabe, H. Kawamura, M. K. Mannoor, S. R. Morshed, T. Abo. 2001. Intensive generation of NK1.1^- extrathymic T cells in the liver by injection of bone marrow cells isolated from mice with a mutation of polymorphic major histocompatibility complex antigens. Immunology 102:450.[Medline]
30. Osman, Y., T. Kawamura, T. Naito, K. Takeda, L. van Kaer, K. Okumura, T. Abo. 2000. Activation of hepatic NKT cells and subsequent liver injury following administration of -galactosylceramide. Eur. J. Immunol. 30:1919.[Medline]
31. Ito, S., M. Ueno, S. Nishi, M. Arakawa, Y. Ikarashi, T. Saitoh, M. Fujiwara. 1992. Histological characteristics of lupus nephritis in F₁ mice with chronic graft-versus-host reaction across MHC class II difference. Autoimmunity 12:79.[Medline]
32. Kameyama, H., T. Kawamura, T. Naito, M. Bannai, K. Shimamura, K. Hatakeyama, T. Abo. 2001. Size of the population of CD4⁺ natural killer T cells in the liver is maintained without supply by the thymus during adult life. Immunology 104:135.[Medline]
33. Good, M. F.. 1991. The implications for malaria vaccine programs if memory T cells from non-exposed humans can respond to malaria antigens. Curr. Opin. Immunol. 3:496.[Medline]
34. Winger, L. A., R. E. Sinden. 1992. Immunoprotection in mice susceptible to waning memory against the pre-erythrocytic stages of malaria after validated immunization with irradiated sporozoites of Plasmodium berghei. Parasitol. Res. 78:427.[Medline]
35. Wenisch, C., H. Wenisch, H. C. Bankl, M. Exner, W. Graninger, S. Looareesuwan, H. Rumpold. 1996. Detection of anti-neutrophil cytoplasmic antibodies after acute Plasmodium falciparum malaria. Clin. Diagn. Lab. Immunol. 3:132.[Abstract]
36. Lloyd, C. M., I. Collins, A. J. Belcher, N. Manuelpillai, A. O. Wozencraft, N. A. Staines. 1994. Characterization and pathological significance of monoclonal DNA-binding antibodies from mice with experimental malaria infection. Infect. Immun. 62:1982.[Abstract/Free Full Text]
37. Ribeiro, C. D., C. Alfred, L. Monjour, M. Gentilini. 1984. Normal frequency of anti-thyroglobulin antibodies in hyperendemic areas of malaria: relevance to the understanding of autoantibody formation in malaria. Trop. Geogr. Med. 36:323.[Medline]
38. Kataaha, P. K., C. A. Facer, S. M. Mortazavi-Milani, H. Stierle, E. J. Holborow. 1984. Stimulation of autoantibody production in normal blood lymphocytes by malaria culture supernatants. Parasite Immunol. 6:481.[Medline]
39. Ribeiro, C. T., S. de Roquefeuil, P. Druilhe, L. Monjour, J. C. Homberg, M. Gentilini. 1984. Abnormal anti-single stranded (ss) DNA activity in sera from Plasmodium falciparum infected individuals. Trans. R. Soc. Trop. Med. Hyg. 78:742.[Medline]
40. Gleichmann, E., S. T. Pals, A. G. Rolink, T. Radaszkiewicz, H. Gleichmann. 1984. Graft-versus-host reactions: clues to the etiopathology of a spectrum of immunological diseases. Immunol. Today 5:324.
41. Via, C. S., G. M. Shearer. 1988. T-cell interactions in autoimmunity: insights from a murine model of graft-versus-host disease. Immunol. Today 9:207.[Medline]
42. Hsu, D. H., K. W. Moore, H. Spits. 1992. Differential effects of IL-4 and IL-10 on IL-2-induced IFN- synthesis and lymphokine-activated killer activity. Int. Immunol. 4:563.[Abstract/Free Full Text]
43. Emoto, M., Y. Emoto, S. H. E. Kaufmann. 1995. IL-4 producing CD4⁺TCR^int liver lymphocytes: influence of thymus, ₂-microglobulin and NK1.1 expression. Int. Immunol. 7:1729.[Abstract/Free Full Text]
44. Emoto, M., Y. Emoto, S. H. E. Kaufmann. 1997. CD8⁺TCR^intermediate lymphocytes expressing skewed TCRV repertoire in the liver of aged athymic nu/nu mice. J. Immunol. 158:1041.[Abstract]
45. Emoto, M., H.-W. Mittrücker, R. Schmits, T. W. Mak, S. H. E. Kaufmann. 1999. Critical role of leukocyte function-associated antigen-1 in liver accumulation of CD4⁺ NKT cells. J. Immunol. 162:5094.[Abstract/Free Full Text]

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