Transient Appearance of Hepatic Natural Killer Cells with High Cytotoxicity and Unique Phenotype in Very Young Mice

There were few natural killer (NK) cells in the liver in very young mice at the age of 1-2 weeks. This was because the cell yield from the liver of young mice was low. The percentage of NK cells in the liver of young mice, however, was almost comparable with that in the liver of adult mice. Lymphocytes were isolated from the liver and spleen of C57BL/6 (B6) mice, and NK cytotoxicity and phenotype were herein examined in this study. NK cytotoxicity was extremely high in the liver of very young mice. This phenomenon was seen in the liver of various normal mouse strains. In contrast, the appearance of high cytotoxicity was not seen in NK cells of the spleen, irrespective of mouse strains. The quality of NK cells in the liver of young mice was different from that in adult mice. NK cells in the liver of young mice were mainly CD69(+)Mac-1(-) Fas ligand(+), whereas those in the liver of adult mice were CD69(-)Mac-1(+) Fas ligand(-). These results revealed that the quality of hepatic NK cells changes in the process of ageing. Namely, liver NK cells in very young mice temporarily show the highest NK cytotoxicity and a unique activated phenotype. Physiological meaning of the present phenomenon was discussed.

CD161+ T (NT) cells exist predominantly in human intestinal epithelium as well as in liver

It has been reported that human CD161 (NKR-P1A)+ T cells are counterparts of murine natural T (NT) cells and predominantly accumulate in the liver. However, NT cells in the human intestine have not been well analysed. The aim of this study was to assess the existence of NT cells in human intestinal epithelium and determine their phenotypical characterization. Intra-epithelial lymphocytes (IEL) were isolated from surgical specimens (jejunum, ileum and colon). The surface phenotype of IEL was analysed using a FACScan and compared with that of mononuclear cells (MNC) from other organs. CD161+ T cells were abundant in human intestinal epithelium as well as the liver. The majority of CD161+ T cells in IEL were CD8+ cells. About 50% of CD161+ T cells in hepatic lymphocytes (HL) expressed CD56, whereas only 14% of CD161+ T cells in IEL expressed CD56. The jejunum showed the greatest abundance of CD161+ T cells among the intestinal regions investigated. These results suggest that CD161+ T (NT) cells predominantly exist in human intestinal epithelium and may play an important role in local immunity.

Calcitonin-producing pancreatic somatostatinoma: report of a case

A 59-year-old woman was hospitalized due to a 1-year history of diarrhea and weight loss. Echography and computed tomography of the abdomen revealed a 10 x 7 cm solid mass in the tail of the pancreas and gallstones, while selective celiac angiography revealed the presence of a hypervascular mass. High levels of somatostatin and calcitonin were detected in the plasma, 70 pg/ml (normal range <28 pg/ml) and 5550 pg/ml (normal range 37 +/- 8 pg/ml), respectively. This tumor was thus removed by means of a distal pancreatectomy and a splenectomy. After the pancreatic tumor was removed, the elevated levels of plasma somatostatin and calcitonin returned to the normal ranges, and the persistent diarrhea also dramatically disappeared. A postoperative immunohistochemical study showed the tumor cells to be diffusely positive for somatostatin and calcitonin. These results clearly indicate this patient to be a case of calcitonin-producing pancreatic somatostatinoma.

Participation of NK1.1+ T cells in the rejection of lpr alphabetaT cells when bone marrow cells of lpr mice are transplanted into B6 mice

When C57BL/6 (B6) mice were irradiated (9 Gy) and received bone marrow (BM) cells of B6-lpr/lpr mouse origin (i.e., lpr-->B6), all mice died within 6 days. In the irradiated B6 mice, radioresistant CD3 IL-2Rbeta+ NK cells and IL-2Rbeta+ CD3int cells (i.e., CD3int cells of extrathymic origin) remained, especially in the liver. There were two subsets, NK1.1+ and NK1.1-, among the IL-2Rbeta+ CD3int cells. However, the NK1.1+ subset (i.e., NK1.1- T cells) was much more radioresistant, and the majority of CD3int cells belonged to this subset in irradiated mice. The expansion of lymphocytes from injected BM cells did not occur in the irradiated B6 mice. However, such expansion did take place in irradiated B6-lpr/lpr mice injected with both BM cells of B6-lpr/lpr and B6 origin. As a result, the mice subjected to BM cells survived. Irradiated B6 mice were treated in vivo with anti-NK1.1 mAb or anti-asialoGM1 antibody to eliminate NK cells alone or both NK cells and NK1.1+ T cells. When irradiated B6 mice were pretreated with anti-NK1.1 mAb, the mice could survive. These results suggest that intact NK1.1+ T cells of extrathymic origin may recognize abnormal BM cells with the lpr gene and inhibit the expansion of lymphocytes, including abnormal double-negative CD4 8 cells, in B6-lpr/lpr mice. To inhibit the expansion of lymphocytes, mechanisms other than Fas ligand/Fas molecules on extrathymic T cells may be responsible.

An allogeneic microenvironment influences the phenotype of intermediate T-cell receptor cells expanding in MRL-lpr/lpr mice

MRL-lpr/lpr (lpr) mice fall victim to autoimmune disease owing to a lymphoproliferative disorder mainly of double-negative (DN) CD4- CD8- alpha beta T cells expressing a low density of interleukin-2 receptor beta-chain (IL-2R beta). It was previously revealed that the lpr gene is a defective Fas gene, into which an early transposon (ETn) of retrovirus is transfected. As a result of the failure of apoptosis, intermediate T-cell receptor (TCR) cells (i.e. TCRint cells) with DN phenotype abnormally accumulate in the periphery of lpr mice. We investigated herein how these TCRint cells are selected in terms of CD4, CD8 and TCR in lpr mice. When a whole fraction of mononuclear cells (MNC) in various immune organs of lpr mice was injected into scid mice (allogeneic circumstance), CD8+ TCRint cells mainly expanded. They had a high density of IL-2R beta. This was true when bone marrow cells of lpr mice were injected into scid mice. On the other hand, when MNC of the spleen and bone marrow in lpr mice were injected into irradiated (9 Gy) lpr mice (syngeneic circumstance), the major expanding cells were DN TCRint cells expressing a low density of IL-2R beta. A cell-sorting experiment for purified fractions demonstrated that only CD8- cells reconstituted TCRint cells in scid mice. Namely, DN CD4- CD8- cells as well as CD4+ cells which once acquired the mature phenotype, no longer switched their phenotype. These results suggest that the phenotype of TCRint cells is influenced by the surrounding microenvironment.

Circadian rhythm of leucocytes and lymphocytes subsets and its possible correlation with the function of the autonomic nervous system

There are physiological variations in the levels of leucocytes. Among these, the circadian rhythm is very important in terms of the magnitude. Since newly identified lymphocyte subsets (i.e. extrathymic T cells) have recently been detected, a comprehensive study of the circadian rhythm was conducted. All leucocytes were found to vary in number or proportion with a circadian rhythm and were classified into two groups. One group--granulocytes, macrophages, natural killer (NK) cells, extrathymic T cells, gammadelta T cells, and CD8+ subset--showed an increase in the daytime (i.e. daytime rhythm). The other group--T cells, B cells, alphabeta T cells, and CD4+ subset--showed an increase at night. Humans are active and show sympathetic nerve dominance in the daytime. Interestingly, granulocytes and lymphocyte subsets with the daytime rhythm were found to carry a high density of adrenergic receptors. On the other hand, lymphocyte subsets with the night rhythm carried a high proportion of cholinergic receptors. Reflecting this situation, exercise prominently increased the number of cells with the daytime rhythm. These results suggest that the levels of leucocytes may be under the regulation of the autonomic nervous system.

Neonatal granulocytosis is a postpartum event which is seen in the liver as well as in the blood

In a recent series of studies, we demonstrated that stress in humans and animals, with resultant sympathetic nerve strain, induces severe granulocytosis, because granulocytes carry adrenergic receptors on the surface. Because activated granulocytes produce free radicals and superoxides, they sometimes induce tissue damage if the stress is too strong or continuous. Human neonates are also known to show high levels of granulocytes in the peripheral blood. In this study, we investigated whether such neonatal granulocytosis are a stress-associated response at birth. Both human and mouse materials, before and after birth, were used. The number of leukocytes in the blood, as well as some other factors in the serum, were measured. Although levels of granulocytes were found to be low in fetal humans and mice, they increased sharply after birth. In parallel with this postpartal granulocytosis, transaminases in sera increased transiently. In reference to results of a transient elevation in the levels of catecholamines at birth in mice, all these phenomena resemble stress-associated responses. Indeed, fatty liver and hematopoietic destruction in the liver were also observed in mice and humans. At this time, the production of inducible nitric oxide synthase (iNOS) by granulocytes in the liver was evident. These results suggest that neonatal granulocytosis is a postpartum event which results from various stresses (e.g., oxygen stress) at birth. This event may be responsible for such well-known neonatal phenomena as the termination of fetal hematopoiesis in the liver and as neonatal jaundice.

[Adult bochdalek hernia after playing at a tug of war]

A 38-year-old female was admitted to Shonai Hospital with severe abdominal pain and nausea after playing at a tug of war in the athletic meeting. The X-ray film showed air above the left diaphragm, and CT scan and barium enema revealed the incarcerated transverse colon to the left thoracic cavity. Operation was performed through a thoracotomy. Because of no evidence of trauma, the case was diagnosed as adult Bochdalek hernia. Repair could be done by direct suture and her postoperative course was uneventful.

Identification of nicotinic acetylcholine receptors on lymphocytes in the periphery as well as thymus in mice

The existence of nicotinic acetylcholine receptors (nAChR) on lymphocytes remains controversial. We attempted to show the existence of nAChR on murine lymphocytes. The intraperitoneal injection of nicotine induced the lymphocytosis in the spleen on day 3. Although freshly isolated lymphocytes bound small quantities of fluorescein isothiocyanate (FITC)-conjugated alpha-bungarotoxin (alpha BuTx), they began to bind alpha BuTx after incubation in medium. In contrast to granulocytes, various lymphocyte subsets obtained from various lymphoid organs were found to bind alpha BuTx. Affinity purification of alpha BuTx-binding protein revealed that lymphocytes expressed the same nAChR molecules as those of muscle. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that lymphocytes expressed the alpha-subunit mRNA of nAChR. These results suggest that lymphocytes carry nAChR on the surface and are stimulated directly via their nAChR by parasympathetic nerve stimuli.

Requirement of IL-4 and liver NK1+ T cells for concanavalin A-induced hepatic injury in mice

Con A-induced hepatic injury of mice accompanied by elevated transaminase was inhibited after in vivo depletion of liver NK cells and NK1+ T cells with intermediate TCR by anti-NK1 Ab or anti-IL-2Rbeta Ab. However, depletion of liver NK cells alone by anti-asialo-GM1 Ab did not inhibit hepatic injury. Although depletion of NK1+ T cells inhibited Con A-induced IL-2R expression of CD4+ high TCR (TCRhigh) cells and IL-4 mRNA expression of hepatic mononuclear cells, exogenous IL-4 engendered Con A-induced hepatic injury and endowed the expression of IL-2R of CD4+ TCRhigh cells. It was also found that in vivo treatment with anti-IL-4 Ab before Con A administration inhibited Con A-induced hepatic injury. In addition, although Con A did not induce hepatic injury in MHC class I-deficient mice, exogenous IL-4 again engendered severe hepatic injury in these mice. Further, while serum TNF-alpha levels induced by Con A were greatly decreased in NK1+ T cell-depleted mice and class I-deficient mice, TNF-alpha levels were recovered by exogenous IL-4. These findings reveal that although CD4+ TCRhigh cells in the liver and their production of TNF-alpha are the direct effectors of Con A-induced hepatic injury, liver NK1+ T cells also play an important role in this hepatitis model. Con A hepatitis may serve as an experimental model for human autoimmune hepatitis.

Mouse liver T cells: their change with aging and in comparison with peripheral T cells

Mouse liver contains both IL-2Rbeta- (or low positive) high T-cell receptor (TCR(hi)) cells and IL-2Rbeta+ intermediate TCR (TCR(int)) cells. TCR(int) cells consist of natural killer 1.1 (NK1)+ and NK1- subsets. NK1- TCR(int) cells increase constantly with age whereas TCR(hi) cells decrease. NK1+ TCR(int) cell proportions in the liver increase until middle age and decrease thereafter. Although NK1+ TCR(int) cells in other organs are few regardless of age, NK1- TCR(int) cells gradually appear in other lymphoid organs with aging. Skewed usage of Vbeta7 and Vbeta8 TCR was observed in NK1+ TCR(int) cells in the liver but the predominance was less obvious in NK1- TCR(int) and TCR(hi) cells in the liver and other organs. TCR V alpha14 messenger RNA (mRNA) was detected in NK1+ TCR(int) cells but not in the other two populations. In contrast, although NK1+ TCR(int) cells contain virtually no V alpha11+ T cells, NK1- TCR(int) cells contain a much higher proportion (approximately 12%) of V alpha11+ T cells, whereas approximately 4% of TCR(hi) cells are V alpha11+. NK activities of liver mononuclear cells (MNC) and splenocytes decrease with aging, although the former is always greater than the latter. NK activity of liver MNC is a function of NK cells, partly NK1+ TCR(int) cells but not NK1- TCR(int) cells or TCR(hi) cells. These results suggest that lymphocytes of liver and other organs at old age are no longer occupied solely by conventional thymus-derived T cells, and the increase of extrathymic IL-2Rbeta+ NK1- TCR(int) cells in liver and periphery could be closely related to immunological changes with aging.

Requirement of IL-4 and liver NK1+ T cells for concanavalin A-induced hepatic injury in mice

Con A-induced hepatic injury of mice accompanied by elevated transaminase was inhibited after in vivo depletion of liver NK cells and NK1+ T cells with intermediate TCR by anti-NK1 Ab or anti-IL-2Rbeta Ab. However, depletion of liver NK cells alone by anti-asialo-GM1 Ab did not inhibit hepatic injury. Although depletion of NK1+ T cells inhibited Con A-induced IL-2R expression of CD4+ high TCR (TCRhigh) cells and IL-4 mRNA expression of hepatic mononuclear cells, exogenous IL-4 engendered Con A-induced hepatic injury and endowed the expression of IL-2R of CD4+ TCRhigh cells. It was also found that in vivo treatment with anti-IL-4 Ab before Con A administration inhibited Con A-induced hepatic injury. In addition, although Con A did not induce hepatic injury in MHC class I-deficient mice, exogenous IL-4 again engendered severe hepatic injury in these mice. Further, while serum TNF-alpha levels induced by Con A were greatly decreased in NK1+ T cell-depleted mice and class I-deficient mice, TNF-alpha levels were recovered by exogenous IL-4. These findings reveal that although CD4+ TCRhigh cells in the liver and their production of TNF-alpha are the direct effectors of Con A-induced hepatic injury, liver NK1+ T cells also play an important role in this hepatitis model. Con A hepatitis may serve as an experimental model for human autoimmune hepatitis.

Autologous killing by a population of intermediate T-cell receptor cells and its NK1.1+ and NK1.1- subsets, using Fas ligand/Fas molecules

Self-reactive clones, estimated by anti-V beta monoclonal antibodies (mAb) in conjunction with the Mls system, are confined to a population of intermediate (int) T-cell receptor (TCR) (or CD3) cells (i.e. TCRint cells), but are not found among TCRhigh cells. The next questions to be answered are whether autologous killing is confined to TCRint cells and how such killing is mediated. In this study, 51Cr-labelled thymocytes of syngeneic or allogeneic origin were used as target cells (4-hr assay). When liver and splenic mononuclear cells (MNC) obtained from B6 mice were used as effector cells, prominent autologous killing was seen in liver MNC, but not splenic MNC. Such killing was not seen when thymocytes from B6-lpr/lpr mice (i.e. Fas-) were used as target cells, nor when liver MNC from MRL-gld/gld mice (i.e. Fas ligand-) were used as effector cells (target thymocytes of MRL(-)+/+ mice). Cell separation experiments using a cell sorter revealed that autologous killing was mediated for the most part by CD3int cells, while allogeneic killing was mediated entirely by natural killer (NK) cells, TCRint cells and TCRhigh cells. Among CD3int cells, the NK1.1+ subset (i.e. NK1.1+ T cells) manifested a higher level of autologous killing than did the NK1.1- subset. Consistent with the results of a functional assay, it was found by reverse-transcription-polymerase chain reaction (RT-PCR) assay that CD3int cells among liver MNC showed the expression of Fas ligand mRNA, while thymocytes expressed Fas mRNA. When class I major histocompatibility complex (MHC)- thymocytes (from beta 2-microglobulin-deficient mice) were used as target cells, NK cells, but not CD3int cells, showed potent cytotoxicity. These results suggest that autologous killing is a major function of TCRint cells with self-reactivity, and that such killing is mediated by means of Fas ligand/Fas molecules.

Self-reactive forbidden clones are confined to pathways of intermediate T-cell receptor cell differentiation even under immunosuppressive conditions

It is believed that self-reactive forbidden T-cell clones are generated by 'failure' of the pathway of T-cell differentiation in the thymus, if it is disturbed. We examined how such forbidden clones are generated under immunosuppressive conditions. Mice were treated with an injection of deoxyspergualin, FK506, or cycloporin A. From day 3, the number of cells yielded by various organs decreased. Because of the resistance of intermediate (int) T-cell receptor (TCR) cells (i.e. TCRint cells), they became more prominent in proportion than TCRhigh cells. TCRhigh cells are conventional T cells generated through the mainstream in the thymus, whereas TCRint cells are primordial T cells generated by the extrathymic pathway or an alternative intrathymic pathway. Similar to untreated mice, forbidden V beta 3+ and V beta 11+ clones in C3H/He (Mls-1b2a) mice were confined to TCRint cells after treatment; there was no leakage of forbidden clones into TCRhigh cells in the thymus and periphery. In parallel with the increase in the proportion of TCRint cells, the proportion of forbidden clones also increased under immunosuppressive states, especially in the liver. Liver mononuclear cells isolated from treated mice still had the potential to mediate autologous killing. The present results suggest that the generation of self-reactive clones is highly restricted to the pathways of TCRint cell differentiation even under immunosuppressive conditions.

Groove pancreatitis with recurrent duodenal obstruction. Report of a case successfully treated with pylorus-preserving pancreaticoduodenectomy

Groove pancreatitis is a rare subtype of chronic pancreatitis that is difficult to distinguish from pancreatic carcinoma. Most reported patients have undergone a Whipple procedure because pancreatic cancer was not ruled out. We report a case of groove pancreatitis in a patient who presented with recurrent duodenal obstruction without biliary stricture. The diagnosis of groove pancreatitis was based on characteristic episodes of repeated duodenal obstruction and the absence of radiographic evidence of cancer. Subsequently, our patient underwent a successful pylorus-preserving pancreaticoduodenectomy (PPPD). PPPD is a favorable alternative to the Whipple operation for duodenal obstruction resulting from this disease.

Absolute dependence of T cell receptor(hi) cell generation and relative dependence of T cell receptor(int) cell generation on the thymus

Recent evidence indicates that conventional T cells are generated by the mainstream of T cell differentiation in the thymus and acquire a high density of T cell receptor expression (i.e. TCRhi). In contrast, primordial T cells (or NK1.1+ T cells) are generated by the extrathymic pathways or an alternative intrathymic pathway and express an intermediate density of TCR (i.e. TCRint). To obtain further evidence, it was examined how thymus grafting influenced the distribution of T cell populations in athymic nude mice. When BALB/c nu/nu mice were engrafted with thymocyte-depleted BALB/c+/+ fetal thymi, two changes emerged after grafting: nude mice generated TCRhi cells de novo in the periphery as well as in the grafted thymi, and the absolute number of interleukin-2 receptor beta chain+ TCRint cells increased prominently in number in the periphery. Among thymic hormones tested, the administration of thymosin alpha induced a slight expansion of CD3int cells in nude mice. To examine a possible interaction of TCRint cells with TCRhi cells in the periphery, B6 nu/nu mice (Ly5.2+) were injected with TCRhi cells purified from the spleen of B6 Ly5.1 congenic mice. In this case, TCRint (Ly5.2+) cells expanded well in all tested organs of nude mice. These results suggest that the generation of TCRhi cells is absolutely dependent on the thymus and that TCRint cells expand under the influence of the thymus (humoral) and due to interaction with thymus-derived conventional T cells.

Restricted appearance of self-reactive clones into T cell receptor intermediate cells in neonatally thymectomized mice with autoimmune disease

Neonatally thymectomized (NTx) mice fall victim to such autoimmune diseases as gastritis and pancreatitis with aging. Self-reactive T cell clones are known to be consistently generated through TCR intermediate (i.e. TCRint) cell differentiation in normal mice (i.e. via the extrathymic pathways and an alternative intrathymic pathway). It was investigated whether the generation of such clones in NTx mice follows this rule or whether they are generated by default via mainstream T cell differentiation in the thymus. The majority of T cells generated in NTx mice were TCRint cells in all organs tested. In contrast to athymic mice, which carry only TCRint cells with aging, a leaky appearance of high TCR (i.e. TCRhi) cells emerged in the lymph nodes and other organs of NTx mice. Self-reactive clones estimated by anti-Vbeta monoclonal antibodies in conjunction with the Mls system were confined to TCRint cells in all tested organs, including a target organ, the stomach, in NTx mice. A leaky population of TCRhi cells did not contain a significant number of self-reactive clones. Moreover, such self-reactive clones among TCRint cells in NTx mice with autoimmune disease were shown to be nonanergic in the proliferation assay. The present results suggest that the generation of self-reactive clones is totally due to TCRint cell differentiation, although it is still undetermined whether the expanding TCRint cell population is generated via the extrathymic pathway or an alternative intrathymic pathway. It is shown here not to be due to a failure of the TCRhi cell-differentiation pathway in NTx mice.

Cytotoxic activity against tumour cells mediated by intermediate TCR cells in the liver and spleen

Morphological and phenotypic characterization in previous studies has indicated that intermediate (int) T-cell receptor (TCR) cells or T natural killer (TNK) cells may stand at an intermediate position between NK cells and high TCR cells of thymic origin in phylogenetic development. In this study, a functional study on cytotoxic activity against various tumour targets was performed in each purified subset. When a negative selection method entailing in vivo injection of anti-asialo GM, antibody or anti-interleukin (IL)-2R beta monoclonal antibody (mAb) was applied, IL-2R beta 1 CD3 NK cells were found to have the highest NK activity while IL-2R beta 1 int CD3 (or TCR) cells had a lower level of the NK activity. High CD3 cells (freshly isolated) did not have any such activity. Sorting experiments further revealed that the NK function mediated by int CD3 cells was augmented when they were exposed to anti-CD3 mAb. anti-TCR alpha beta, or anti-TCR-delta mAb. This phenomenon was not observed in NK cells and high CD3 cells. More importantly, when anti-CD3 mAb (or anti-TCR mAb) was added to the assay culture, int CD3 cells became cytotoxic against even NK-resistant tumour (Fc gamma R-. Fas+) targets. Liver mononuclear cells or int CD3 cells exposed to anti-CD3 mAb for 6 hr showed an elevated level of perforin in their cytoplasms. The present results suggest that int CD3 cells are usually non-cytotoxic against various tumours but become functional after being stimulated via the TCR CD3 complex.

Existence of a small population of IL-2R beta hi TCRint cells in SCG and MRL-lpr/lpr mice which produce normal Fas mRNA and Fas molecules from the lpr gene

Mice carrying the lpr gene, SCG and MRL-lpr/lpr mice, were used to characterize the phenotype and lpr gene of abnormally proliferating T cells in these mice. A major population which expanded in these mice were T cells expressing intermediate (int) levels of T cell receptor (TCR) (and CD3) and the phenotype of interleukin-2 receptor (IL-2R) beta lo alpha- (possibly abnormal TCRint cells). The levels of TCRhi cells of thymic origin (generated through the mainstream of T cell differentiation in the thymus) profoundly decreased after the onset of disease. However, a small population of normal TCRint cells (i.e. IL-2R beta hi alpha-) were also found to exist in all tested organs. For example, the majority of abnormal IL-2R beta lo TCRint cells were CD4-8- CD2-, while normal IL-2R beta hi TCRint cells were a mixture of single-positive cells (mainly CD8+), CD4-8- cells and CD2+ cells. Moreover, normal TCRint cells preferentially produced normal Fas mRNA and Fas molecules from the lpr gene. This phenomenon explains the leaky appearance of normal Fas mRNA and Fas molecules in mice carrying the lpr gene. It is suggested that a small population of IL-2R beta hi TCRint cells are resistant to the lpr genetic abnormality.

Origin of CD57+ T cells which increase at tumour sites in patients with colorectal cancer

Human T cells carrying natural killer (NK) markers, CD57 or CD56 antigens, appear to be distinguishable from other T cell subsets in terms of their granular lymphocyte morphology and their numerical increase in patients with AIDS and in recipients of bone marrow transplantation. At the beginning of this study, we observed that CD57+ T cells as well as CD56+ T cells were abundant at tumour sites in many patients with colorectal cancer. Since all these findings for CD57+ T cells are quite similar to those of extrathymic T cells seen in mice, we investigated how CD57+ T cells are distributed to various immune organs in humans. They were found to be present mainly in the bone marrow and liver, but to be completely absent in the thymus. Similar to the case of extrathymic T cells in mice, they were observed to consist of double-negative CD4-8- subsets as well as single-positive subsets (preponderance of CD8+ cells), and to contain a considerable proportion of gamma delta T cells. These features are striking when compared with those of CD57- T cells, which are characterized by an abundance of CD4+ subsets and alpha beta T cells. Not only at tumour sites but also in the peripheral blood, some patients with colorectal cancer displayed elevated levels of CD57+ cells. These results suggest that CD57+ T cells may be of extrathymic origin, possibly originating in the bone marrow and liver, and may be associated with tumour immunity, similar to another extrathymic population of CD56+ T cells in humans.

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

Experiments to date have revealed a population of T cells that carry intermediate (int) levels of TCR (or CD3) and express IL-2R beta-chain (IL-2R beta) in mouse liver. Such int TCR cells also reside in other immune organs, although in low numbers. On the other hand, NK1.1+ T cells with int TCR do reside in the thymus and other peripheral organs. To determine the relationship of two types of cells, we characterized int CD3 cells and NK1.1+ T cells throughout the organs in terms of the phenotype, V beta repertoire, and morphology. Although both IL-2R beta+ T cells and NK1.1+ T cells are classified as int CD3 cells, NK1.1+ T cells are present within int CD3 cells. The majority of int CD3 cells in the liver and thymus were NK1.1+, whereas the minority of such cells in the spleen, lymph nodes, and bone marrow were NK1.1+. Among int CD3 cells, double-negative (DN) CD4-8- cells and/or CD4+ were abundant in NK1.1+ subset, whereas CD8+ cells were generally abundant in NK1.1- subset. Self-reactive V beta+ clones estimated by the M1s system were distributed to both NK1.1+ and NK1.1- subsets. High CD3 cells in the thymus and other organs contained neither DN cells nor forbidden clones. Int CD3 cells had the morphology of granular or agranular lymphocytes carrying perforin. Among int CD3 cells, NK1.1+ subset had a higher level of perforin-positive cells than NK1.1- subset. These results clearly demonstrate the relationship between int TCR cells and NK1.1+ T cells in various organs.

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

Experiments to date have revealed a population of T cells that carry intermediate (int) levels of TCR (or CD3) and express IL-2R beta-chain (IL-2R beta) in mouse liver. Such int TCR cells also reside in other immune organs, although in low numbers. On the other hand, NK1.1+ T cells with int TCR do reside in the thymus and other peripheral organs. To determine the relationship of two types of cells, we characterized int CD3 cells and NK1.1+ T cells throughout the organs in terms of the phenotype, V beta repertoire, and morphology. Although both IL-2R beta+ T cells and NK1.1+ T cells are classified as int CD3 cells, NK1.1+ T cells are present within int CD3 cells. The majority of int CD3 cells in the liver and thymus were NK1.1+, whereas the minority of such cells in the spleen, lymph nodes, and bone marrow were NK1.1+. Among int CD3 cells, double-negative (DN) CD4-8- cells and/or CD4+ were abundant in NK1.1+ subset, whereas CD8+ cells were generally abundant in NK1.1- subset. Self-reactive V beta+ clones estimated by the M1s system were distributed to both NK1.1+ and NK1.1- subsets. High CD3 cells in the thymus and other organs contained neither DN cells nor forbidden clones. Int CD3 cells had the morphology of granular or agranular lymphocytes carrying perforin. Among int CD3 cells, NK1.1+ subset had a higher level of perforin-positive cells than NK1.1- subset. These results clearly demonstrate the relationship between int TCR cells and NK1.1+ T cells in various organs.

Self-reactive T cell clones in a restricted population of interleukin-2 receptor beta+ cells expressing intermediate levels of the T cell receptor in the liver and other immune organs

T cells expressing high levels of the T cell receptor (TCRhigh) differentiate in the major intrathymic pathway and then distribute to the peripheral immune organs, whereas T cells expressing intermediate levels of the TCR (TCRint) differentiate in both extrathymic pathways and an alternative intrathymic pathway and localize in unique sites, including the liver and thymic medulla. Since TCRint cells constitutively express interleukin-2 receptor beta-chain (IL-2R beta), two-color staining for CD3 (or TCR) and IL-2R beta clearly distinguished IL-2R beta+ CD3int (or TCRint) cells from IL-2R beta-, CD3high cells. CD3int cells may be considered to be primordial T cells based on their phenotype, morphology and other functional properties. In this study, using anti-V beta mAb in conjunction with the endogenous superantigen Mls, the distribution of self-reactive clones among T cells generated in all of the above pathways was investigated in mice. Self-reactive T cell clones were confined to IL-2R beta+, CD3int cells, in all of the organs tested. A significant proportion of self-reactive clones was never identified among CD3high cells in the thymus and peripheral immune organs in either young (8 week old) or old (50 week old) mice. Possibly reflecting their self-reactivity, CD3int cells, but neither NK cells nor CD3high cells had a potent cytotoxic effect against a syngeneic hepatoma in the presence of anti-CD3 mAb. These results raise the possibility that CD3int cells seen in the liver and thymus might belong to a similar primordial lineage of T cells, and that self-reactive clones are not generated through the major intrathymic pathway, but only through extrathymic pathways and an alternative intrathymic pathway.

Characterization of intermediate T-cell receptor cells expanding in the liver, thymus and other organs in autoimmune lpr mice: parallel analysis with their normal counterparts

Autoimmune MRL-lpr/lpr (lpr) mice were previously demonstrated to have an abnormal proliferation of intermediate T-cell receptor (TCR) cells of extrathymic origin in the liver. Despite this situation, thymectomy in lpr mice resulted in amelioration of autoimmune disease. To understand the underlying mechanism, we investigated associated T-cell differentiation in the thymus and other organs of these mice. When the disease was evoked, T cells with extrathymic properties, i.e. intermediate TCR-alpha beta cells expressing double-negative (DN) CD4-8- phenotype and interleukin-2 (IL-2) receptor beta-chain, became prominent not only in the liver, but also in the thymus. Such thymic T cells mainly resided in the medulla. A small-scale localization of such T cells was seen in the thymic medulla even in normal control mice. There was a heterogeneity among intermediate TCR cells in terms of the composition of DN cells and the expression of CD2 and B220 antigens, depending on the organs and the sites in the same organ. Intermediate TCR cells in the liver, thymus and autoimmune target organs (e.g. kidney) contained a high proportion of the active form (CD2+B220-), while intermediate TCR cells accumulating in peripheral organs, the spleen and lymph nodes, were mainly of the inactive form (CD2-B220+). The active form had an ability to proliferate in response to IL-2 and SEB, whereas the inactive form did not. The present results suggest that the proliferation of intermediate TCR cells occur at multiple sites; this may explain the effect of thymectomy, namely, the retarded onset of disease, in lpr mice.

Extrathymic T cells stand at an intermediate phylogenetic position between natural killer cells and thymus-derived T cells

A series of recent studies have revealed that extrathymic pathways of T cell differentiation exist at multiple sites in mice and humans. In terms of their properties, extrathymic T cells may stand at an intermediate position between natural killer (NK) cells and thymus-derived T cells in phylogenetic development. It is speculated that primitive lymphocytes such as NK cells and extrathymic T cells develop from primordial macrophages in intraepithelial regions of e.g., the intestine, skin and liver. In this regard, the immune system of the bone marrow and thymus is relatively recent, developing after the emergence of living beings onto the land (i.e., amphibia). A complete elimination of self-reactive T cell clones occurs in mainstream intrathymic T cell differentiation and a consistent generation of such clones occurs through the extrathymic pathways. Therefore, thymus-derived T cells are efficient for processing foreign antigens, whereas extrathymic T cells recognize abnormal self-cells. Although thymus-derived T cells play the major role in youth, extrathymic T cells may play rather a pivotal role with aging and under conditions of malignancy, intracellular infections, pregnancy, and autoimmune diseases.

Adhesion molecules on intermediate TCR cells. I. Unique expression of adhesion molecules, CD44+ L-selectin-, on intermediate TCR cells in the liver and the modulation of their adhesion by hyaluronic acid

In addition to thymus-derived T cells, it was demonstrated recently that extrathymically differentiated T cells exist in the liver and other immune organs of mice. Since such extrathymic T cells have T-cell receptors (TCR) of intermediate intensity (i.e. intermediate TCR cells) and constitutively express IL-2 receptor beta-chain (IL-2R beta) similar to natural killer (NK) cells, they are easily distinguished from thymus-derived T cells with a TCR-bright+ IL-2R beta- phenotype (i.e. bright TCR cells). In the present study, the expression of adhesion molecules CD44 and L-selectin was compared between these T-cell subsets. Intermediate TCR cells in the liver and other organs were found to be CD44+ L-selectin- and, inversely, bright TCR cells were CD44- L-selectin+. CD3- IL-2R beta+ NK cells were also estimated to be CD44+ L-selectin-. Hyaluronic acid, which is known to adhere to a CD44 ligand, bound to intermediate TCR cells, but not to bright TCR cells. Among many extracellular matrices, hyaluronic acid induced a prominent decrease in the numbers and proportions of intermediate TCR cells and NK cells in the liver from 6 to 24 hr after in vivo administration. The half-life span of injected hyaluronic acid was approximately 7 hr in the plasma. These results suggest that the CD44 molecule, which is uniquely expressed on intermediate TCR cells and NK cells, is eventually associated with their adhesion to the sinusoidal walls in the liver.

Increase in the proportion of granulated CD56+ T cells in patients with malignancy

Evidence is presented for the existence of a unique T cell population which expressed one of the natural killer (NK) markers, CD56 antigen, in humans. Although such CD56+ T cells were a minor population in the peripheral blood (< 10%), they were abundant in the liver (up to 50%), which was recently demonstrated to be a major organ for extrathymic T cell differentiation in mice. As in the case of extrathymic T cells in mice, these CD56+ T cells in humans contained a higher proportion of gamma delta T cells than did CD56- T cells, contained double-negative CD4-8- cells, and had the morphology of large granular lymphocytes. This unique population of CD56+ T cells tended to be elevated in the blood and among tumour-infiltrating lymphocytes in patients with colorectal cancer, especially in advanced cases. These results raise the possibility that, as in mice, CD56+ T cells with extrathymic T cell properties may also be associated with tumour immunity in humans.

Predominant activation of extrathymic T cells during melanoma development of metallothionein/ret transgenic mice

Transgenic mice that carried a metallothionein/ret fusion gene (Tg.MT/ret mice) exhibited severe pigmentation in their skin after birth and developed melanomas at adult ages. To learn how the immune system was modulated during melanoma development in these mice, lymphocytes in various organs were examined. An immunofluorescence cell analysis was focused on the simultaneous characterization of T cells of extrathymic and thymic origins and performed at three time points: 6 weeks of age (before melanoma development), 20 weeks (after melanoma development), and 30 weeks (end stage). The number and proportion of extrathymic T cells with TCR of intermediate intensity (i.e., intermediate TCR cells) were markedly increased in the liver over entire periods of life. These intermediate TCR cells constitutively expressed IL-2R beta, contained double-negative CD4-8- cells, and predominated V beta 8+ cells. Such intermediate TCR cells were also abundant among tumor infiltrating lymphocytes. In contrast, an increase in the number and proportion of regular T cells with TCR of bright intensity (i.e., bright TCR cells of thymic origin) was seen at only a limited period in various organs. Rather, at the late phase, thymic atrophy was induced and accompanied with the decrease in the proportion of bright TCR cells in the periphery. These results suggested that extrathymic T cells generated in the liver might play important roles in tumor immunity.

Glucocorticoid independence of acute thymic involution induced by lymphotoxin and estrogen

Acute thymic involution is known to be induced under conditions of physical stress, bacterial infections, and malignancies. It is speculated that glucocorticoids, tumor necrosis factor (TNF), and other factors may act as mediators for the thymic involution under such conditions. It was herein investigated whether either lymphotoxin (TNF beta) or estrogen could induce thymic involution without the help of glucocorticoids. Interestingly, both lymphotoxin or estrogen alone induced profound thymic involution even in adrenalectomized mice. In contrast to glucocorticoids, which induce lymphocytopenia throughout the organs, lymphotoxin and estrogen did not induce lymphocytopenia in the peripheral organs. More importantly, lymphotoxin and estrogen rather stimulated extrathymic T cells in the liver and other organs. These results suggest that lymphotoxin and estrogen per se might be important regulators of immune systems.

Similarities and differences between extrathymic T cells residing in mouse liver and intestine

Extrathymic T cells in the hepatic sinusoids and intraepithelial lymphocytes (IEL) in the intestine of mice have both similar and different properties. In this study, both types of extrathymic T cells in mice were further characterized. Lymphocytes obtained from systemic immune organs, including the lamina propria and Peyer's patches, were also compared. Extrathymic T cells in both the liver and the intestine contained a large proportion of gamma delta T cells and expressed the alpha alpha homodimer of CD8. They became more prominent in athymic nude mice and in normal mice with aging, while disappearing in scid mice. Extrathymic T cells in the liver, on the other hand, had TCR of intermediate intensity (i.e., intermediate TCR cells) and IL-2 receptor beta-chains (IL-2R beta) of high intensity, similar to NK cells, whereas IEL had TCR of bright intensity and consisted of cells with both low and high levels of IL-2R beta. Thymus-derived T cells did not express IL-2R beta at all, at least at their resting conditions. Intermediate TCR cells included double-negative CD4-8- cells as well as single-positive cells. In contrast, IEL contained both double-positive (DP) CD4+8+ cells and single-positive cells. More precisely, IEL gamma delta T cells were mainly IL-2R beta + and single-positive (mainly CD8+), while IEL alpha beta T cells were mainly IL-2R beta- and contained both DP CD4+8+ cells and single-positive cells. CD4+ cells were more predominant than CD8+ cells in the liver, while CD8+ cells were overwhelmingly predominant in the intestine. These results suggest that both intermediate TCR cells and IEL are generated as primitive T cells in phylogeny, but later develop along independent pathways at their respective sites.

Radioresistance of intermediate TCR cells and their localization in the body of mice revealed by irradiation

Extrathymic generation of T cells in the liver and in the intestine was recently demonstrated. We investigated herein whether such T cells, especially those in the liver, are present in other organs of mice. This investigation is possible employing our recently introduced method with which even a minor proportion of extrathymic, intermediate TCR cells in organs other than the liver can be identified. Intermediate TCR cells expressed higher levels of IL-2R beta and LFA-1 than bright TCR cells (i.e., T cells of thymic origin) as revealed by two-color staining. Although intermediate TCR cells were present at a small proportion in the spleen and thymus, they predominated in these organs after irradiation (9 Gy) and bone marrow reconstitution, or after low dose irradiation (6 Gy). This was due to that intermediate TCR cells were relatively radioresistant, whereas bright TCR cells were radiosensitive. Microscopic observation and immunochemical staining showed that intermediate TCR cells in the spleen localized in the red pulp and those in the thymus localized in the medulla. These intermediate TCR cells displayed a large light scatter, similar to such cells in the liver. The present results suggest that intermediate TCR cells may proliferate at multiple sites in the body.

Characterization of intermediate TCR cells in the liver of mice with respect to their unique IL-2R expression

We previously demonstrated that T cells with intermediate TCR intensity (i.e., intermediate TCR cells) which possibly generate extrathymically are preferentially present in the liver of mice. This population was further characterized with respect to the expression of IL-2 receptor (IL-2R) and others. Two-color staining for CD3 (or TCR alpha beta) and IL-2R alpha (and beta) demonstrated that intermediate TCR cells as well as NK cells constitutively expressed IL-2R beta but not IL-2R alpha. A small number of intermediate TCR cells was also identified in other immune organs by using this staining method. In vivo and in vitro stimulation experiments revealed that regular, bright TCR cells, which originally lacked the expression of both IL-2R alpha and beta, acquired the highest expression of IL-2R alpha and beta, while intermediate TCR cells did not. These results suggested, in conjunction with their other properties demonstrated here, that intermediate TCR cells might be more primitive T cells than regular T cells of thymic origin.

Activation of extrathymic T cells in the liver during liver regeneration following partial hepatectomy

Partial hepatectomy was performed in C57BL/6 mice to investigate whether extrathymic T cells in the liver are activated during liver regeneration. This study is based on the finding that in mice with malignant tumours, extrathymic T cells in the liver are activated and yet the intrathymic pathway is suppressed (i.e. thymic atrophy). Attention was therefore focused on whether a similar phenomenon is induced during benign cell regeneration. Extrathymic T cells were identified using the two-colour immunofluorescence test for CD3 and interleukin-2 receptor beta-chain (IL-2R beta) [or lymphocyte function-associated antigen-1 (LFA-1)] antigens. They were estimated to be intermediate CD3+ [or T-cell receptor (TcR)] cells with high expressions of IL-2R beta and LFA-1. It was demonstrated that the proportion and number of intermediate CD3+ cells increased in the early phase (days 2-4 after partial hepatectomy), and that the thymus was inversely atrophic at the same time. This raised the possibility that extrathymic T cells may also be responsible for regulation of normal cell regeneration.

Ontogeny and development of extrathymic T cells in mouse liver

We previously demonstrated that the liver may be a major site of extrathymic T-cell differentiation in mice. In the present study, the ontogeny and subsequent development of such T cells in the liver and other organs were investigated. This study was possible because these T cells have T-cell receptors (TcR) of intermediate intensity (i.e. intermediate TcR cells) and constitutively express a high level of interleukin-2 receptor beta chain (IL-2R beta). Therefore the two-colour staining for CD3 (or alpha beta TcR) and IL-2R beta identifies even a small proportion of intermediate TcR cells. The total numbers of mononuclear cells obtained from the liver, thymus and spleen varied from foetal to adult life. Especially in the liver, many haematopoietic cells were present in the parenchymal space at the foetal stage. There were no lymphocytes in the sinusoidal lumen at this period. In contrast, lymphocytes appeared in the hepatic sinusoids after birth and increased with ageing. Phenotypic analysis revealed that intermediate TcR cells appeared in the liver and spleen on Day 4 after birth. Bright TcR cells of thymic origin were also present in the peripheral organs on Day 4. Thereafter, intermediate TcR cells increased in the liver, whereas bright TcR cells increased in the periphery as a function of age. Similarly, thymectomized and congenitally athymic mice had mainly intermediate TcR cells in the liver and, to some extent, periphery. It is concluded that intermediate TcR cells, possibly of extrathymic origin, are generated only after birth and expand with ageing.

Relative resistance of intermediate TCR cells to anti-CD3 mAb in mice in vivo and their partial functional characterization

In addition to T cells differentiated in the thymus, T cells, possibly of extrathymic origin, were recently demonstrated in the liver of mice. These T cells are characterized by the expression of intermediate TCR and contain double-negative CD4-8- cells. A further characterization of intermediate TCR cells was carried out. When mice were injected ip with anti-CD3 mAb, bright TCR cells (i.e., regular T cells) and intermediate TCR cells were reduced on Day 3, depending on the amount of mAb. Because of the resistance of intermediate TCR cells to treatment, injection of an appropriate dose of antibody (i.e., 100 micrograms/mouse) eliminated most bright TCR cells, but not intermediate TCR cells. This dose revealed that a significant proportion of intermediate TCR cells also reside in the periphery. Hepatic and splenic mononuclear cells (MNC), in which intermediate TCR cells became abundant after treatment, showed a unique response to T cell mitogens and IL-2. Thus, the intermediate TCR cell-enriched population could not respond to a T cell mitogen, Con A, but responded well to a super antigen, staphylococcal enterotoxin B, and IL-2. MNC obtained from athymic nude mice, which comprise only intermediate TCR cells, responded in the same manner. These findings revealed that intermediate TCR cells are present not only in the liver but also in the periphery, and that they have a unique function distinct from regular T cells.

Prostaglandin E1 enhances hepatic portal venous flow by dilating the portal vascular bed in 70% hepatectomized dog

The effects of portal, hepatic arterial and femoral venous administration of prostaglandin E1 (PGE) on portal venous flow (PVF) and hepatic arterial flow HAF were examined before and after 70% hepatectomy in anesthetized dogs. In the hepatectomized condition, portal venous administration of PGE (0.5 microgram/kg/min) caused an increase in PVF without any change in systemic arterial pressure (SAP). HAF was unchanged following the injection. The portal effect of PGE on PVF was dose-dependent, and a reduction in portal venous resistance was seen. However, the same dose of PGE failed to change PVF under intact liver conditions. Hepatic arterial administration of PGE (0.5 microgram/kg/min) brought no significant change in PVF or HAF, with or without hepatectomy. Femoral venous administration of PGE (0.5 micrograms/kg/min) produced an increase in PVF concomitant with a significant decrease in SAP. HAF showed no change after the injection. A decrease in PVR was seen only in the hepatectomized condition. It is concluded that PGE is potent in increasing PVF in the hepatectomized condition, and the portal vasculature is involved as the site of action.

Activation of extrathymic T cells in the liver and reciprocal inactivation of intrathymic T cells by bacterial stimulation

We recently demonstrated that the liver might be a major site of extrathymic T cell differentiation, including both alpha beta and gamma delta T cells. This extrathymic pathway in the liver, which has a relatively minor role in normal young mice, is activated in mice under bacterial stimulation. In the present study, we investigated how the extrathymic and intrathymic T cell differentiations were mutually related in mice injected intravenously with 10(8) heat-killed Escherichia coli. Three days after stimulation, extrathymic T cells in the liver were observed to be prominently activated in terms of increases in the total number of cells yielded, spontaneous cell proliferation in in vitro culture, and intermediate alpha beta TCR cells. Intermediate alpha beta TCR cells were extrathymic T cells uniquely seen in the liver. However, at the same time intrathymic T cells were profoundly inactivated, showing decreases in the number of thymocytes (more than 90% atrophy), spontaneous cell proliferation, and dull TCR cells with double positive CD4+8+ phenotype. With time, these responses were reversed and normal states were regained. These results suggested that extrathymic and intrathymic T cells are always activated or inactivated in the opposite direction, and that the liver and the thymus are dynamic immune organs. It raises the possibility that the extrathymic T cell differentiation in the liver and the intrathymic T cell differentiation may be reciprocally regulated by certain factors.