Jα33+ MAIT cells play a protective role in TNBS induced intestinal inflammation

BACKGROUND/AIMS

Mucosa-associated T-lymphocyte (MAIT) cells that are selectively accumulated in the intestinal mucosa may be involved in immune regulation. MAIT cells are determined by their Vα7.2-Jα33 (human)/Vα19-Jα33 (mice) invariant chain. The encoding DNA sequences of Human Jα33 and mouse Jα33 are identical. In order to study the role of MAIT cells in IBD we produced anti-Jα33 antibody to detect MAIT cells in TNBS induced IBD models.

METHODOLOGY

Colitis was induced by TNBS in male BALB/c mice. Jα33+MAIT cells from normal mice were transferred into TNBS induced mice as donors. Colitis severity was evaluated clinically and histologically, under the condition of transferred Jα33+MAIT cells.

RESULTS

The mRNA and protein expression levels of MAIT aTCR in the colonic mucosa were decreased after TNBS administration; Jα33+MAIT cells were aggregated in spleen after TNBS administration. The disease activity index (DAI) which was determined by weight loss, stool consistency and intestinal bleeding, increased after TNBS administration. Transferred Jα33+MAIT cells significantly degrade the increase in the disease activity index scores.

CONCLUSIONS

Taken together, the results indicated that the aggregation of Jα33+MAIT cells in intestinal mucosa improved TNBS-induced colitis. We conclude that Jα33+MAIT cells play a protective role in TNBS induced intestinal inflammation.

EBV promotes human CD8 NKT cell development

The reports on the origin of human CD8⁺ Vα24⁺ T-cell receptor (TCR) natural killer T (NKT) cells are controversial. The underlying mechanism that controls human CD4 versus CD8 NKT cell development is not well-characterized. In the present study, we have studied total 177 eligible patients and subjects including 128 healthy latent Epstein-Barr-virus(EBV)-infected subjects, 17 newly-onset acute infectious mononucleosis patients, 16 newly-diagnosed EBV-associated Hodgkin lymphoma patients, and 16 EBV-negative normal control subjects. We have established human-thymus/liver-SCID chimera, reaggregated thymic organ culture, and fetal thymic organ culture. We here show that the average frequency of total and CD8⁺ NKT cells in PBMCs from 128 healthy latent EBV-infected subjects is significantly higher than in 17 acute EBV infectious mononucleosis patients, 16 EBV-associated Hodgkin lymphoma patients, and 16 EBV-negative normal control subjects. However, the frequency of total and CD8⁺ NKT cells is remarkably increased in the acute EBV infectious mononucleosis patients at year 1 post-onset. EBV-challenge promotes CD8⁺ NKT cell development in the thymus of human-thymus/liver-SCID chimeras. The frequency of total (3% of thymic cells) and CD8⁺ NKT cells (∼25% of NKT cells) is significantly increased in EBV-challenged chimeras, compared to those in the unchallenged chimeras (<0.01% of thymic cells, CD8⁺ NKT cells undetectable, respectively). The EBV-induced increase in thymic NKT cells is also reflected in the periphery, where there is an increase in total and CD8⁺ NKT cells in liver and peripheral blood in EBV-challenged chimeras. EBV-induced thymic CD8⁺ NKT cells display an activated memory phenotype (CD69⁺CD45RO^hiCD161⁺CD62L^lo). After EBV-challenge, a proportion of NKT precursors diverges from DP thymocytes, develops and differentiates into mature CD8⁺ NKT cells in thymus in EBV-challenged human-thymus/liver-SCID chimeras or reaggregated thymic organ cultures. Thymic antigen-presenting EBV-infected dendritic cells are required for this process. IL-7, produced mainly by thymic dendritic cells, is a major and essential factor for CD8⁺ NKT cell differentiation in EBV-challenged human-thymus/liver-SCID chimeras and fetal thymic organ cultures. Additionally, these EBV-induced CD8⁺ NKT cells produce remarkably more perforin than that in counterpart CD4⁺ NKT cells, and predominately express CD8αα homodimer in their co-receptor. Thus, upon interaction with certain viruses, CD8 lineage-specific NKT cells are developed, differentiated and matured intrathymically, a finding with potential therapeutic importance against viral infections and tumors.

We show that the average frequency of total and CD8⁺ NKT cells in PBMCs from 128 healthy latent EBV-infected subjects is significantly higher than in 17 patients with acute lytic EBV infection, 16 EBV-associated HL patients, and 16 EBV-negative normal subjects. The frequency of total and CD8⁺ NKT cells is remarkably increased in the lytic EBV-infected patients at year 1 post-onset. EBV-challenge promotes total and CD8⁺ NKT cell development in the thymus and liver of human-thymus/liver-SCID chimeras, compared to those in the unchallenged chimeras. After EBV-challenge, a proportion of NKT precursors diverges from DP thymocytes, develops and differentiates into mature CD8⁺ NKT cells in thymus in EBV-challenged human-thymus/liver-SCID chimeras or reaggregated thymic organ cultures. Thymic EBV-infected dendritic cells are required for this process. IL-7 is an essential factor for CD8⁺ NKT cell differentiation. EBV-induced CD8⁺ NKT cells produce remarkably more perforin, and predominately express CD8αα homodimer. CD8 lineage-specific NKT cells are developed and differentiated intrathymically upon EBV-exposure, a finding with potential therapeutic importance against viral infections and tumors.

EBV-induced human CD8+ NKT cells suppress tumorigenesis by EBV-associated malignancies

The underlying mechanism of the protective and suppressive role of NKT cells in human tumor immunosurveillance remains to be fully elucidated. We show that the frequencies of CD8(+) NKT cells in patients with EBV-associated Hodgkin's lymphoma or nasopharyngeal carcinoma are significantly lower than those in healthy EBV carriers. These CD8(+) NKT cells in tumor patients are also functionally impaired. In human-thymus-severe combined immunodeficient (hu-thym-SCID) chimeras, EBV challenge efficiently promotes the generation of IFN-gamma-biased CD8(+) NKT cells. These cells are strongly cytotoxic, drive syngeneic T cells into a Th1 bias, and enhance T-cell cytotoxicity to EBV-associated tumor cells. Interleukin-4-biased CD4(+) NKT cells are predominately generated in unchallenged chimeras. These cells are noncytotoxic, drive syngeneic T cells into a Th2 bias, and do not affect T-cell cytotoxicity. In humanized xenogeneic tumor-transplanted hu-thym-SCID chimeras, adoptive transfer with EBV-induced CD8(+) NKT cells significantly suppresses tumorigenesis by EBV-associated malignancies. EBV-induced CD8(+) NKT cells are necessary and sufficient to enhance the T-cell immunity to EBV-associated malignancies in the hu-thym-SCID chimeras. CD4(+) NKT cells are synergetic with CD8(+) NKT cells, leading to a more pronounced T-cell antitumor response in the chimeras cotransferred with CD4(+) and CD8(+) NKT cells. Thus, immune reconstitution with EBV-induced CD8(+) NKT cells could be a useful strategy in management of EBV-associated malignancies.

CD19+CD5+ B cells in primary IgA nephropathy

The source of IgA and the mechanism for deposition of IgA in the mesangium remain unknown for primary IgA nephropathy. Because CD19(+)CD5(+) B cells are important producers of IgA and contribute to several autoimmune diseases, they may play an important role in IgA nephropathy. In this study, flow cytometry, quantitative PCR, and confocal microscopy were used to assess the frequency, distribution, Ig production, CD phenotypes, cytokine production, and sensitivity to apoptosis of CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney biopsies of 36 patients with primary IgA nephropathy. All patients with IgA nephropathy were significantly more likely to have CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney biopsies than were five control subjects and 10 patients with active systemic lupus erythematosus. The 33 patients who had IgA nephropathy and responded to treatment demonstrated a significant decrease in CD19(+)CD5(+) B cells in the peripheral blood, peritoneal fluid, and kidney (all P < 0.01). In the three patients who had IgA nephropathy and did not respond to treatment, the frequency of CD19(+)CD5(+) B cells did not change. CD19(+)CD5(+) B cells isolated from patients with untreated IgA nephropathy expressed higher levels of IgA, produced more IFN-gamma, and were more resistant to CD95L-induced apoptosis than cells isolated from control subjects and patients with lupus; these properties reversed with effective treatment of IgA nephropathy. In conclusion, these results strongly suggest that CD19(+)CD5(+) B cells play a prominent role in the pathogenesis of primary IgA nephropathy.

Essential role of sphingosine-1-phosphate receptor 1-bearing CD8+CD44+CCR7+ T cells in acute skin allograft rejection

A subset of naturally formed sphingosine-1-phosphate receptor 1 (S1P1)-bearing CD8(+)CD44(+)CCR7(+) memory T cells has been identified in transplant recipient BALB/c (H-2(d)) mice. The frequency of this subset of memory T cells is significantly increased in the spleen, lymph nodes and skin grafts in the recipient BALB/c mice during acute skin allograft rejections. The immune-reconstitution with CD8(+)CD44(+)CCR7(+)S1P1(+) memory T cells facilitates acute skin allograft rejection in SCID mice. Being Th1-polarized and cytotoxic, CD8(+)CD44(+)CCR7(+)S1P1(+) memory T cells proliferate and differentiate immediately into effectors upon encountering allo-antigens. A siRNA against S1P1 inhibits CD8(+)CD44(+)CCR7(+)S1P1(+) memory T cell-mediated acute skin allograft rejection in SCID mice by means of knocking-down S1P1-expression. CCL21 mutant (CCL21-DeltaCT) has been used to compete with wild-type CCL21 in the course of binding to CCR7. Combined administration of siRNA S1P1 and CCL21-DeltaCT significantly prolongs the survival of skin allograft in the recipient BALB/c mice by means of inhibiting accumulation of CD8(+)CD44(+)CCR7(+)S1P1(+) memory T cells in the spleen and the skin grafts. Our data provide direct evidence that S1P1 and CCR7 are involved in the proliferation and trafficking of CD8(+)CD44(+)CCR7(+)S1P1(+) memory T cells. S1P1 may serve as a functional marker for CD8(+)CD44(+)CCR7(+) memory T cells. Targeting CD8(+)CD44(+)CCR7(+)S1P1(+) T cells may be a useful strategy to prolong the survival of allograft transplant.

CCL19 and CXCL13 synergistically regulate interaction between B cell acute lymphocytic leukemia CD23+CD5+ B Cells and CD8+ T cells

Interacting with T cells, cytokine-producing B cells play a critical protective role in autoimmune diseases. However, the interaction between malignant B and T cells remains to be fully elucidated. In a previous study, we have reported that ligation of CCL19-CCR7 and CXCL13-CXCR5 activates paternally expressed gene 10 (PEG10), resulting in an enhancement of apoptotic resistance in B-cell acute lymphocytic leukemia (B-ALL) CD23+CD5+ B cells. Here, we report that B-ALL CD23+CD5+ B cells produce IL-10 at high level, which can be further elevated by costimulation with CCL19 and CXCL13. CCL19/CXCL13-activated B-ALL CD23+CD5+ B cells, in turn, increase IL-10 expression in syngeneic CD8+ T cells in a B cell-derived IL-10-dependent manner and requiring a cell-cell contact. IL-10 secreted from B-ALL CD23+CD5+ B cells in vitro impairs tumor-specific CTL responses of syngeneic CD8+ T cells. The impairment of cytotoxicity of syngeneic CD8+ T cells is escalated by means of CCL19/CXCL13-induced up-regulation of IL-10 from B-ALL CD23+CD5+ B cells. Moreover, using a short hairpin RNA to knockdown PEG10, we provide direct evidence that increased expression of PEG10 in B-ALL CD23+CD5+ B cells is involved in malignant B-T cell interaction, contributing to the up-regulation of IL-10 expression, as well as to the impairment of cytotoxicity of syngeneic CD8+ T cells. Thus, malignant B-ALL CD23+CD5+ B cells play an immunoregulatory role in controlling different inflammatory cytokine expressions. IL-10 may be one of the critical cellular factors conferring B-ALL CD23+CD5+ B cells to escape from host immune surveillance.

CXC Chemokine Ligand 13 and CC Chemokine Ligand 19 Cooperatively Render Resistance to Apoptosis in B Cell Lineage Acute and Chronic Lymphocytic Leukemia CD23+CD5+B Cells

CXCL13/CXCR5 and CCL19/CCR7 play a quite important role in normal physiological conditions, but the functions of both chemokine/receptor pairs in pathophysiological events are not well-investigated. We have investigated expression and functions of CXCL13/CXCR5 and CCL19/CCR7 in CD23+CD5+ and CD23+CD5- B cells from cord blood (CB) and patients with B cell lineage acute or chronic lymphocytic leukemia (B-ALL or B-CLL). CXCR5 and CCR7 are selectively expressed on B-ALL, B-CLL, and CB CD23+CD5+ B cells at high frequency, but not on CD23+CD5- B cells. Although no significant chemotactic responsiveness was observed, CXCL13 and CCL19 cooperatively induce significant resistance to TNF-alpha-mediated apoptosis in B-ALL and B-CLL CD23+CD5+ B cells, but not in the cells from CB. B-ALL and B-CLL CD23+CD5+ B cells express elevated levels of paternally expressed gene 10 (PEG10). CXCL13 and CCL19 together significantly up-regulate PEG10 expression in the same cells. We have found that CXCL13 and CCL19 together by means of activation of CXCR5 and CCR7 up-regulate PEG10 expression and function, subsequently stabilize caspase-3 and caspase-8 in B-ALL and B-CLL CD23+CD5+ B cells, and further rescue the cells from TNF-alpha-mediated apoptosis. Therefore, we suggest that normal lymphocytes, especially naive B and T cells, use CXCL13/CXCR5 and CCL19/CCR7 for migration, homing, maturation, and cell homeostasis as well as secondary lymphoid tissues organogenesis. In addition, certain malignant cells take advantages of CXCL13/CXCR5 and CCL19/CCR7 for infiltration, resistance to apoptosis, and inappropriate proliferation.

Different neurotropic pathogens elicit neurotoxic CCR9- or neurosupportive CXCR3-expressing microglia

What mechanism that determines microglia accomplishing destructive or constructive role in CNS remains nebulous. We report here that intracranial priming and rechallenging with Toxoplasma gondii in mice elicit neurotoxic CCR9+ Irg1+ (immunoresponsive gene 1) microglia, which render resistance to apoptosis and produce a high level of TNF-alpha; priming and rechallenging with lymphocytic choriomeningitis virus elicit neurosupportive CXCR3+ Irg1- microglia, which are sensitive to apoptosis and produce a high level of IL-10 and TGF-beta. Administration of CCR9 and/or Irg1 small interfering RNA alters the frequency and functional profiles of neurotoxic CCR9+ Irg1+ and neurosupportive CXCR3+ Irg1- microglia in vivo. Moreover, by using a series of different neurotropic pathogens, including intracellular parasites, chronic virus, bacteria, toxic substances, and CNS injury to intracranially prime and subsequent rechallenge mice, the bi-directional elicitation of microglia has been confirmed as neurotoxic CCR9+ Irg1+ and neurosupportive CXCR3+ Irg1- cells in these mouse models. These data suggest that there exist two different types of microglia, providing with a novel insight into microglial involvement in neurodegenerative and neuroinflammatory pathogenesis such as Alzheimer's disease and AIDS dementia.

All roads lead to Rome: pathways of NKT cells promoting asthma

NKT cells are the prominent manipulator in asthma development. Asthmatic NKT cells migrate from thymus, spleen, liver and bone marrow into blood vessels, and then concentrate in airway bronchi mucosa. This recruitment is dependent on high expression of CCR9 and engagement of CCL25/CCR9. NKT cells promote asthma in two different pathways. One is an indirect pathway. NKT cells contact with CD3(+) T cells and induce them secreting large quantity of Th2 cytokines (IL-4, IL-13), which requires the participation of dentritic cells and the synergic signaling of CCL25/CCR9 and CD226. The other is a direct pathway. Circulating asthmatic NKT cells selectively highly express Th1 cytokines (IFN-gamma). Once reached airway epithelium, most NKT cells shift to Th2-bias, highly expressing IL-4, IL-13, but not IFN-gamma. Both pathways lead to airway hyperresponsiveness and inflammation, asthma development. Comparing to the well documented suppressive regulatory T cells, CD4(+)CD25(+) T cells, NKT cells perform as a novel active regulator in asthma. These recent understanding of NKT cells performance in the development of asthma might unveil new therapy targets and management strategies for asthma.

V alpha 24-invariant NKT cells from patients with allergic asthma express CCR9 at high frequency and induce Th2 bias of CD3+ T cells upon CD226 engagement

We have demonstrated that Valpha24(+)Vbeta11(+) invariant (Valpha24(+)i) NKT cells from patients with allergic asthma express CCR9 at high frequency. CCR9 ligand CCL25 induces chemotaxis of asthmatic Valpha24(+)i NKT cells but not the normal cells. A large number of CCR9-positive Valpha24(+)i NKT cells are found in asthmatic bronchi mucosa, where high levels of Th2 cytokines are detected. Asthmatic Valpha24(+)i NKT cells, themselves Th1 biased, induce CD3(+) T cells into an expression of Th2 cytokines (IL-4 and IL-13) in cell-cell contact manner in vitro. CD226 are overexpressed on asthmatic Valpha24(+)i NKT cells. CCL25/CCR9 ligation causes directly phosphorylation of CD226, indicating that CCL25/CCR9 signals can cross-talk with CD226 signals to activate Valpha24(+)i NKT cells. Prestimulation with immobilized CD226 mAb does not change ability of asthmatic Valpha24(+)i NKT cells to induce Th2-cytokine production, whereas soluble CD226 mAb or short hairpin RNA of CD226 inhibits Valpha24(+)i NKT cells to induce Th2-cytokine production by CD3(+) T cells, indicating that CD226 engagement is necessary for Valpha24(+)i NKT cells to induce Th2 bias of CD3(+) T cells. Our results are providing with direct evidence that aberration of CCR9 expression on asthmatic Valpha24(+)i NKT cells. CCL25 is first time shown promoting the recruitment of CCR9-expressing Valpha24(+)i NKT cells into the lung to promote other T cells to produce Th2 cytokines to establish and develop allergic asthma. Our findings provide evidence that abnormal asthmatic Valpha24(+)i NKT cells induce systemically and locally a Th2 bias in T cells that is at least partially critical for the pathogenesis of allergic asthma.