CD56 marks an effector T cell subset in the human intestine

Natural Killer T-like Cells: Immunobiology and Role in Disease

CD56+ T cells are generally recognized as a distinct population of T cells and are categorized as NKT-like cells. Although our understanding of NKT-like cells is far from satisfactory, it has been shown that aging and a number of disease situations have impacted these cells. To construct an overview of what is currently known, we reviewed the literature on human NKT-like cells. NKT-like cells are highly differentiated T cells with "CD1d-independent" antigen recognition and MHC-unrestricted cell killing. The genesis of NKT-like cells is unclear; however, it is proposed that the acquisition of innate characteristics by T cells could represent a remodeling process leading to successful aging. Additionally, it has been shown that NKT-like cells may play a significant role in several pathological conditions, making it necessary to comprehend whether these cells might function as prognostic markers. The quantification and characterization of these cells might serve as a cutting-edge indicator of individual immune health. Additionally, exploring the mechanisms that can control their killing activity in different contexts may therefore result in innovative therapeutic alternatives in a wide range of disease settings.

Steroid receptor coactivator-3 inhibition generates breast cancer antitumor immune microenvironment

BACKGROUND

The tumor immune microenvironment (TIME) generated by cancer-infiltrating immune cells has a crucial role in promoting or suppressing breast cancer progression. However, whether the steroid receptor coactivator-3 (SRC-3) modulates TIME to progress breast cancer is unclear. Therefore, the present study evaluates whether SRC-3 generates a tumor-promoting TIME in breast tumors using a syngeneic immune-intact mouse model of breast cancer.

METHODS

We employed E0771 and 4T1 breast cancer in immune-intact syngeneic female C57BL/6 and BALB/c mice, respectively. SI-2, a specific small-molecule inhibitor of SRC-3, was administered daily (2.5 mg/kg) to E0771 and 4T1 breast tumor-bearing immune-intact mice. In addition, SRC-3 knockdown (KD)-E0771 and SRC-3 KD-4T1 cells and their parental breast cancer cells were injected into their syngeneic immune-intact female mice versus immune-deficiency mice to validate that the host immune system is required for breast tumor suppression by SRC-3 KD in immune-intact mice. Furthermore, tumor-infiltrating immune cells (such as CD4+, CD8+, CD56+, and Foxp3+ cells) in E0771 and 4T1 breast cancers treated with SI-2 and in SRC-3 KD E0771 and 4T1 breast cancers were determined by immunohistochemistry. Additionally, cytokine levels in SI-2-treated and SRC-3 KD E0771 breast tumors and their control cancers were defined with a Mouse Cytokine Array.

RESULTS

SRC-3 inhibition by SI-2 significantly suppressed the progression of breast cancer cells (E0771 and 4T1) into breast cancers in immune-intact syngeneic female mice. SRC-3 KD-E0771 and -4T1 breast cancer cells did not produce well-developed tumors in immune-intact syngeneic female mice compared to their parental cells, but SRC-3 KD breast cancers were well developed in immune-defective host mice. SRC-3 inhibition by SI-2 and SRC-3 KD effectively increased the numbers of cytotoxic immune cells, such as CD4+ and CD8+ T cells and CD56+ NK cells, and Interferon γ (Ifng) in breast cancers compared to vehicle. However, SI-2 treatment reduced the number of tumor-infiltrating CD4+/Foxp3+ regulatory T (Treg) cells compared to vehicle treatment. In addition, SRC-3 inhibition by SI-2 and SRC-3 KD increased C-X-C motif chemokine ligand 9 (Cxcl9) expression in breast cancer to recruit C-X-C motif chemokine receptor 3 (Cxcr3)-expressing cytotoxic immune cells into breast tumors.

CONCLUSIONS

SRC-3 is a critical immunomodulator in breast cancer, generating a protumor immune microenvironment. SRC-3 inhibition by SI-2 or SRC-3 KD activates the Cxcl9/Cxcr3 axis in breast tumors and enhances the antitumor immune microenvironment to suppress breast cancer progression.

Cellular Origins and Pathogenesis of Gastrointestinal NK- and T-Cell Lymphoproliferative Disorders

The intestinal immune system, which must ensure appropriate immune responses to both pathogens and commensal microflora, comprises innate lymphoid cells and various T-cell subsets, including intra-epithelial lymphocytes (IELs). An example of innate lymphoid cells is natural killer cells, which may be classified into tissue-resident, CD56bright NK-cells that serve a regulatory function and more mature, circulating CD56dim NK-cells with effector cytolytic properties. CD56bright NK-cells in the gastrointestinal tract give rise to indolent NK-cell enteropathy and lymphomatoid gastropathy, as well as the aggressive extranodal NK/T cell lymphoma, the latter following activation by EBV infection and neoplastic transformation. Conventional CD4+ TCRαβ+ and CD8αβ+ TCRαβ+ T-cells are located in the lamina propria and the intraepithelial compartment of intestinal mucosa as type 'a' IELs. They are the putative cells of origin for CD4+ and CD8+ indolent T-cell lymphoproliferative disorders of the gastrointestinal tract and intestinal T-cell lymphoma, NOS. In addition to such conventional T-cells, there are non-conventional T-cells in the intra-epithelial compartment that express CD8αα and innate lymphoid cells that lack TCRs. The central feature of type 'b' IELs is the expression of CD8αα homodimers, seen in monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL), which primarily arises from both CD8αα+ TCRαβ+ and CD8αα+ TCRγδ+ IELs. EATL is the other epitheliotropic T-cell lymphoma in the GI tract, a subset of which arises from the expansion and reprograming of intracytoplasmic CD3+ innate lymphoid cells, driven by IL15 and mutations of the JAK-STAT pathway.

Analysis of Vδ1 T cells in clinical grade melanoma-infiltrating lymphocytes

γδ T cells, including Vδ1 and Vδ2 T cells, can recognize tumor-associated ligands neglected by conventional αβ T cells in a MHC-independent manner. Little is known regarding the anticancer potential and the possibility to isolate and expand Vδ1 T cells to therapeutically relevant numbers. In this study, we have detected low frequencies of Vδ1 T cells among tumor-infiltrating lymphocyte (TIL) products for adoptive cell transfer generated from melanoma metastases. An increased frequency of Vδ1 T cells was found among the cell products from patients with an advanced disease stage. Vδ1 T cells displayed in vitro antitumor activities and sufficient proliferative potential to generate over 1 × 10⁹ cells using current protocols for T cell transfer. Infusion of Vδ1 T cells together with high numbers of αβ TILs in a clinical trial was safe and well tolerated. These data suggest that Vδ1 T cells should be further scrutinized as a potentially useful tool for the treatment of patients with metastatic melanoma.

A narrative review of central nervous system involvement in acute leukemias

Acute leukemias (both myeloid and lymphoblastic) are a group of diseases for which each year more successful therapies are implemented. However, in a subset of cases the overall survival (OS) is still exceptionally low due to the infiltration of leukemic cells in the central nervous system (CNS) and the subsequent formation of brain tumors. The CNS involvement is more common in acute lymphocytic leukemia (ALL), than in adult acute myeloid leukemia (AML), although the rates for the second case might be underestimated. The main reasons for CNS invasion are related to the expression of specific adhesion molecules (VLA-4, ICAM-1, VCAM, L-selectin, PECAM-1, CD18, LFA-1, CD58, CD44, CXCL12) by a subpopulation of leukemic cells, called “sticky cells” which have the ability to interact and adhere to endothelial cells. Moreover, the microenvironment becomes hypoxic and together with secretion of VEGF-A by ALL or AML cells the permeability of vasculature in the bone marrow increases, coupled with the disruption of blood brain barrier. There is a single subpopulation of leukemia cells, called leukemia stem cells (LSCs) that is able to resist in the new microenvironment due to its high adaptability. The LCSs enter into the arachnoid, migrate, and intensively proliferate in cerebrospinal fluid (CSF) and consequently infiltrate perivascular spaces and brain parenchyma. Moreover, the CNS is an immune privileged site that also protects leukemic cells from chemotherapy. CD56/NCAM is the most important surface molecule often overexpressed by leukemic stem cells that offers them the ability to infiltrate in the CNS. Although asymptomatic or with unspecific symptoms, CNS leukemia should be assessed in both AML/ALL patients, through a combination of flow cytometry and cytological analysis of CSF. Intrathecal therapy (ITT) is a preventive measure for CNS involvement in AML and ALL, still much research is needed in finding the appropriate target that would dramatically lower CNS involvement in acute leukemia.

Tissue-Resident Lymphocytes Across Innate and Adaptive Lineages

Lymphocytes are an integral component of the immune system. Classically, all lymphocytes were thought to perpetually recirculate between secondary lymphoid organs and only traffic to non-lymphoid tissues upon activation. In recent years, a diverse family of non-circulating lymphocytes have been identified. These include innate lymphocytes, innate-like T cells and a subset of conventional T cells. Spanning the innate-adaptive spectrum, these tissue-resident lymphocytes carry out specialized functions and cross-talk with other immune cell types to maintain tissue integrity and homeostasis both at the steady state and during pathological conditions. In this review, we provide an overview of the heterogeneous tissue-resident lymphocyte populations, discuss their development, and highlight their functions both in the context of microbial infection and cancer.

CD8dim but not CD8bright cells positive to CD56 dominantly express KIR and are cytotoxic during visceral leishmaniasis

This study reports a structural and functional heterogeneity of CD8⁺CD56⁺NKT cells, which usually decrease quantitatively during visceral leishmaniasis. Based on fluorescence intensity of CD8 receptors on CD56⁺NKT cells, two populations of CD8⁺CD56⁺NKT cells have been identified. These cells were recognized as CD8^dimCD56⁺NKT and CD8^brightCD56⁺NKT cells. We further analyzed the functional nature of CD8^dim and CD8^bright positive CD56⁺NKT cells. In comparison to CD8^brightCD56⁺NKT cells, a significantly higher percentage of CD8^dimCD56⁺NKT cells expressed KIR during VL. The percentage of CD8^dimCD56⁺NKT cells expressing KIR was found 4 fold higher in VL as compared to healthy subjects. But, the difference was insignificant in case of CD8^brightCD56⁺NKT cells. CD8⁺CD56⁺NKT cells release granzyme B to kill the infected cells. A categorical difference was also observed in the function of CD8^dimCD56⁺NKT and CD8^brightCD56⁺NKT cells during visceral leishmaniasis. The percentage of granzyme B expressing CD8^dimCD56⁺NKT cells was 2.83 fold higher in VL compared to healthy subjects. But, there was no significant difference in granzyme B expressing CD8^brightCD56⁺NKT cells in samples from healthy and VL subjects. However, within VL subject, the percentage of granzyme B expressing CD8^dimCD56⁺NKT cells was 5.7 fold higher in comparison to CD8^brightCD56⁺NKT cells. This study concludes that CD8^dimCD56⁺NKT cells are more cytotoxic than CD8^brightCD56⁺NKT cells during VL.

Leishmania donovani mediated higher expression of CCL4 induces differential accumulation of CD4+CD56+NKT and CD8+CD56+NKT cells at infection site

Sterile cure from visceralized Leishmania donovani (L. donovani) needs Th1 cell support along with the assistance from innate immune cells, NK cells and NKT cells. NKT cells play as a connecting link between innate and adaptive immune cell and support T helper cell function. Earlier, a categorical function of CD56 positive CD4⁺ or CD8⁺ NKT cells was reported in visceral leishmaniasis (VL). It was observed in in vitro that CD4⁺CD56⁺NKT cells, but not CD8⁺CD56⁺NKT cells, were accumulated at the L. donovani infection site. Therefore, in vitro experiments have been carried out to decipher the mechanism behind preferential accumulation of CD4⁺CD56⁺NKT cells at infection site. In this study, 1.89 fold higher expression of CCL4/MIP-1β was noticed in infected macrophages. The higher expression of CCL4 was correlated with preferential accumulation of CCR5⁺CD4⁺CD56⁺NKT cells and apoptosis of CD8⁺CD56⁺NKT cells at in vitro infection site. The CD4⁺CD56⁺NKT cells were also observed expressing TGF-β dominantly. Interaction of CCL4 chemotaxis was interrupted by blocking, which led to drift back the TGF-β producing CD4⁺CD56⁺NKT cells and promoted CD8⁺CD56⁺NKT cells recruitment in in vitro infection site. CCR5 blockade also reduced CD25 and FoxP3 positive CD4⁺CD56⁺NKT cells in in vitro infection site. Therefore, it was concluded that Leishmania promotes strategic expression of CCL4, which alternately attracts CCR5⁺ cells, mostly expressing regulatory cytokines, at infection site. This reduces the CD8⁺CD56⁺NKT cells at infection site through Smad4 mediated TGF-β expression and activation of caspases. Data indicates that L. donovani induces higher expression of CCL4 in host cell to attract CCR5⁺ cells under its strategic plan to downregulate host immune response.

CD56 in the Immune System: More Than a Marker for Cytotoxicity?

Over the past years, the phenotypic and functional boundaries distinguishing the main cell subsets of the immune system have become increasingly blurred. In this respect, CD56 (also known as neural cell adhesion molecule) is a very good example. CD56 is the archetypal phenotypic marker of natural killer cells but can actually be expressed by many more immune cells, including alpha beta T cells, gamma delta T cells, dendritic cells, and monocytes. Common to all these CD56-expressing cell types are strong immunostimulatory effector functions, including T helper 1 cytokine production and an efficient cytotoxic capacity. Interestingly, both numerical and functional deficiencies and phenotypic alterations of the CD56⁺ immune cell fraction have been reported in patients with various infectious, autoimmune, or malignant diseases. In this review, we will discuss our current knowledge on the expression and function of CD56 in the hematopoietic system, both in health and disease.

Functionally Diverse NK-Like T Cells Are Effectors and Predictors of Successful Aging

The fundamental challenge of aging and long-term survivorship is maintenance of functional independence and compression of morbidity despite a life history of disease. Inasmuch as immunity is a determinant of individual health and fitness, unraveling novel mechanisms of immune homeostasis in late life is of paramount interest. Comparative studies of young and old persons have documented age-related atrophy of the thymus, the contraction of diversity of the T cell receptor (TCR) repertoire, and the intrinsic inefficiency of classical TCR signaling in aged T cells. However, the elderly have highly heterogeneous health phenotypes. Studies of defined populations of persons aged 75 and older have led to the recognition of successful aging, a distinct physiologic construct characterized by high physical and cognitive functioning without measurable disability. Significantly, successful agers have a unique T cell repertoire; namely, the dominance of highly oligoclonal αβT cells expressing a diverse array of receptors normally expressed by NK cells. Despite their properties of cell senescence, these unusual NK-like T cells are functionally active effectors that do not require engagement of their clonotypic TCR. Thus, NK-like T cells represent a beneficial remodeling of the immune repertoire with advancing age, consistent with the concept of immune plasticity. Significantly, certain subsets are predictors of physical/cognitive performance among older adults. Further understanding of the roles of these NK-like T cells to host defense, and how they integrate with other physiologic domains of function are new frontiers for investigation in Aging Biology. Such pursuits will require a research paradigm shift from the usual young-versus-old comparison to the analysis of defined elderly populations. These endeavors may also pave way to age-appropriate, group-targeted immune interventions for the growing elderly population.

Investigating the potential immune role of fish NCAMs: Molecular cloning and expression analysis in mandarin fish

The immune role of NCAMs has been revealed in mammals, yet there is no such report in fish. Hence, we analyzed the molecular characterizations and immune-associated expression patterns of NCAMs in mandarin fish. Three NCAM members, named mfNCAM1a, mfNCAM1b and mfNCAM2, were identified. Among the cDNA sequences of mfNCAMs, AU-rich elements in the 3' UTRs of mfNCAM1b and mfNCAM2 as well as VASE sequences in the fourth Ig-like domain-encoding regions of mfNCAM1a and mfNCAM1b were discovered. Moreover, the syntenic analysis suggested that the duplication of NCAM1 is fish-specific. At mRNA and protein levels, the expression analyses revealed that mfNCAMs existed in both systemic and mucosal immune tissues, and located within lymphoid cells. Upon stimulated either by LPS or poly I:C, the expression level of mfNCAM1a was significantly up-regulated in head kidney, spleen, liver, and gut, whereas mfNCAM1b only in head kidney and liver, and mfNCAM2 only in liver. Additionally, the cells coexpressed mfNCAM1 and mfNCCRP-1 might imply the equivalents to mammalian NK cells. Our finding firstly demonstrates the member-specific immune-related tissue expression pattern and immune activity for fish NCAMs. Current data indicate that mfNCAM2 has little immune activity, while the immune activity of mfNCAM1a exists in more tissues than mfNCAM1b, and mfNCAM1a may tend to respond more actively to viral while mfNCAM1b to bacterial stimulants. Additionally, NCAM1b should be a fish-specific member with unique immune function, judging from its different expression pattern, immune activity as well as phylogenetic relationship to mfNCAM1a.

Effective induction of melanoma-antigen-specific CD8+ T cells via Vγ9γδT cell expansion by CD56(high+) Interferon-α-induced dendritic cells

Dendritic cells (DCs) can be differentiated from CD14+ monocytes in the presence of interferon-α (IFNα) and granulocyte/macrophage-colony stimulating factor (GM-CSF) in vitro and are known as IFN-DCs. Circulating blood CD56+ cells expressing high levels of CD14, HLA-DR and CD86 have been shown to spontaneously differentiate into DC-like cells in vitro after their isolation from blood. We show here that IFN-DCs expressing high levels of CD56 (hereafter, CD56(high+) IFN-DCs) can be differentiated in vitro from monocytes obtained as adherent cells from healthy donors and patients with metastatic melanoma. These cells expressed high levels of CD14, HLA-DR and CD86 and possessed many pseudopodia. These CD56(high+) IFN-DCs may be an in vitro counterpart of the circulating CD56+ CD14+ CD86+ HLA-DR+ cells in blood. Conventional mature DCs differentiated from monocytes as adherent cells in the presence of GM-CSF, IL-4 and TNF-α (hereafter, mIL-4DCs) did not express CD56 or CD14. In contrast to mIL-4DCs, the CD56(high+) IFN-DCs exhibited a stronger capacity to stimulate autologous CD56+ Vγ9γδT cells highly producing IFNγ in the presence of zoledronate and IL-2. The CD56(high+) IFN-DCs possessing HLA-A*0201 effectively induced Mart-1-modified melanoma peptide (A27L)-specific CD8+ T cells through preferential expansion of CD56+ Vγ9γδT cells in the presence of A27L, zoledronate and IL-2. Vaccination with CD56(high+) IFN-DCs copulsed with tumor antigens and zoledronate may orchestrate the induction of various CD56+ immune cells possessing high effector functions, resulting in strong immunological responses against tumor cells. This study may be relevant to the design of future clinical trials of CD56(high+) IFN-DCs-based immunotherapies for patients with melanoma.

Persistent changes in circulating and intestinal γδ T cell subsets, invariant natural killer T cells and mucosal-associated invariant T cells in children and adults with coeliac disease

Coeliac disease is a chronic small intestinal immune-mediated enteropathy precipitated by exposure to dietary gluten in genetically predisposed individuals. The only current therapy is a lifelong gluten free diet. While much work has focused on the gliadin-specific adaptive immune response in coeliac disease, little is understood about the involvement of the innate immune system. Here we used multi-colour flow cytometry to determine the number and frequency of γδ T cells (Vδ1, Vδ2 and Vδ3 subsets), natural killer cells, CD56⁺ T cells, invariant NKT cells, and mucosal associated invariant T cells, in blood and duodenum from adults and children with coeliac disease and healthy matched controls. All circulating innate lymphocyte populations were significantly decreased in adult, but not paediatric coeliac donors, when compared with healthy controls. Within the normal small intestine, we noted that Vδ3 cells were the most abundant γδ T cell type in the adult epithelium and lamina propria, and in the paediatric lamina propria. In contrast, patients with coeliac disease showed skewing toward a predominant Vδ1 profile, observed for both adult and paediatric coeliac disease cohorts, particularly within the gut epithelium. This was concurrent with decreases in all other gut lymphocyte subsets, suggesting a specific involvement of Vδ1 cells in coeliac disease pathogenesis. Further analysis showed that γδ T cells isolated from the coeliac gut display an activated, effector memory phenotype, and retain the ability to rapidly respond to in vitro stimulation. A profound loss of CD56 expression in all lymphocyte populations was noted in the coeliac gut. These findings demonstrate a sustained aberrant innate lymphocyte profile in coeliac disease patients of all ages, persisting even after elimination of gluten from the diet. This may lead to impaired immunity, and could potentially account for the increased incidence of autoimmune co-morbidity.

NKG2D/Ligand dysregulation and functional alteration of innate immunity cell populations in pediatric IBD

BACKGROUND

Dysregulated innate immune responses play an important role in inflammatory bowel disease (IBD). NKG2D innate immunity receptor is a major sensor of tissue damage that, by recognizing multiple stress-induced, cell-associated ligands (MIC-A/B and ULBP1-5), potentiates the effector functions of "innate-like" (γ/δ TcR+, and natural killer receptor+ [NKR+]) T-cell populations. We analyzed the representivity, NKG2D/ligand expression pattern, and functional ability of the major innate immunity cell populations in pediatric IBD patients.

METHODS

We analyzed 41 Crohn's disease (CD) patients, 33 ulcerative colitis (UC) patients, and 51 age-matched non-IBD controls. The expression of NKG2D and its ligands, interferon-gamma (IFN-γ) production, and cytotoxic granule release were assessed by immunostaining and multiparameter cytofluorimetric analysis on circulating and mucosal mononuclear subsets; the inflammatory infiltrate was also characterized by immunohistochemistry.

RESULTS

The expression pattern of NKG2D receptor and its ligands on mucosal and circulating innate immunity populations is severely disturbed in IBD; NKG2D and ligands are upregulated on immune infiltrate in both CD and UC active lesions; receptor/ligand upregulation also occurs on circulating leukocyte populations, where it depends on both disease activity and type (UC vs. CD). Finally, the frequency and effector capability of peripheral blood "innate-like" T-cell populations are also altered in IBD patients.

CONCLUSIONS

The circulating and mucosal innate immunity compartment is phenotypically and functionally altered in pediatric IBD; some alterations may represent a distinctive feature of the pediatric disease condition. The disturbance of NKG2D/ligand pathway may play a role in sustaining immune activation which leads to chronic inflammatory tissue damage.

Phenotypic and functional characterization of human γδ T-cell subsets in response to influenza A viruses

Like αβ T cells, human γδ T cells also have different subsets with distinct characteristics. Whether human Vγ9Vδ2 T cells have functionally different subsets in response to influenza A (fluA) viruses remains unknown. In this study, we show for the first time that both central (CD45RA(-)CD27(+)) and effector (CD45RA(-)CD27(-)) memory Vγ9Vδ2 T cells have similar levels of immediate interferon (IFN) γ and cytotoxic responses to human and avian fluA virus-infected cells. In contrast, CD56(+) Vγ9Vδ2 T cells have significantly higher cytotoxicity against fluA virus-infected cells compared with their CD56(-) counterparts, whereas both subsets have similar IFN-γ responses. We further demonstrate that the CD16-dependent degranulation pathway, but not antibody-dependent cell-mediated cytotoxicity, contribute to the superior cytotoxicity of CD56(+) Vγ9Vδ2 T cells. Our study provides further evidence for the phenotypic and functional characterization of human Vγ9Vδ2 T-cell subsets during fluA virus infection and may help improve the γδ T-cell-based immunotherapy for viral infection.

Potential role of NK cells in the pathogenesis of inflammatory bowel disease

NK cells are a major component of the innate immune system and play an important role in the tissue inflammation associated with autoimmune diseases such as inflammatory bowel disease (IBD). NK cells are unique in bearing both stimulatory and inhibitory receptors specific for MHC class I molecules, and their function is regulated by a series of inhibiting or activating signals. The delicate balance between activation and inhibition that decides NK cell final action provides an opportunity for their possible modulatory effect on specific therapeutic settings. Intestinal NK cells are phenotypically distinct from their counterparts in the blood and resemble “helper” NK cells, which have potentially important functions both in promoting antipathogen responses and in the maintenance of intestinal epithelial homeostasis. NK cell activities have been found to be significantly below normal levels in both remissive and active stages of IBD patients. However, some proinflammatory cytokines (e.g., IL-15, IL-21, and IL-23) could potently induce NK cell activation to secret high levels of proinflammatory cytokines (e.g., IFN-γ and TNF) and promote the cytolytic activities against the target cells. This paper provides the characteristics of intestinal NK cells and their potential role in the pathogenesis of IBD.

CD161 DEFINES EFFECTOR T CELLS THAT EXPRESS LIGHT AND RESPOND TO TL1A-DR3 SIGNALING

Expression of NK cell markers identifies pro-inflammatory T cell subsets in the liver and intestinal immune compartments. Specifically, CD161 is expressed on Th17 cells which play an important role in the regulation of mucosal inflammation. In this study, we characterized human peripheral blood CD161+ T cells as an effector population partially resembling a gut T cell phenotype. CD161+ CD4+ T cells express the gut-associated TNF family member, LIGHT, and respond to crosslinking of DR3, a receptor to another gut-associated cytokine, TL1A. Robust IFN-γ production in response to DR3 signaling correlated with enhanced expression of surface DR3 on CD161+ T cells and co-stimulation with IL12 and IL18. CD161+ T cell effector function was directly demonstrated by activation of responder monocytes in co-culture leading to CD40 upregulation and CD14 downregulation. CD161+ T cells reciprocally responded to activated monocytes, inducing expression of activation marker, CD69, and production of IL2 and IFN-γ, further demonstrating effective CD161+ T cell cross-talk with monocytes. Finally, CD161 defined a subset of T cells that co-express CD56, a second NK marker. Our findings implicate human CD161+ T cells in gut-associated signaling mechanisms, and suggest a monocyte mediated effector function in mucosal inflammation.

Cytokine-induced killer cells are terminally differentiated activated CD8 cytotoxic T-EMRA lymphocytes

OBJECTIVE

Cytokine-induced killer cells (CIK) are CD3(+)CD56(+) T cells with natural killer (NK)-like cytotoxic activity used for the immunotherapy of tumors. We aimed to fully characterize CIK cells and define their ontogeny.

MATERIALS AND METHODS

CIK were generated in vitro by stimulation of peripheral blood mononuclear cells or T-cell subsets with interferon-gamma, anti-CD3 and interleukin-2. They were fully characterized in terms of phenotype, cytotoxic activity, and gene expression with respect to circulating CD3(+)CD56(+) cells, NK cells, and CD56(-) T cells present in CIK cultures.

RESULTS

We demonstrate that CIK are terminally differentiated CD8 T cells that derive from proliferating CD3(+)CD56(-)CD8(+) T cells. They express polyclonal T-cell receptor Vbeta chains and have acquired CD56, NKG2D, and large granular lymphocyte morphology, but lack expression of most NK-specific activating (NKp30, NKp44, NKp46) and inhibitory (KIR2DL1, KIR2DL2, KIR3DL1, NKG2A, CD94) receptors, and can kill K562 targets. Circulating CD3(+)CD56(+) cells are also CD8(+)CD16(-), but are oligoclonal, poorly cytotoxic for K562, and express lower levels of CD56 and NKG2D. Gene profiling of CIK, CD56(-) T and NK cells present at the end of culture shows that differences are much more limited between CIK and CD56(-) T compared to CIK and NK cells. Most of the genes upregulated in CIK cells compared to CD56(-) T cells are part of the tumor necrosis factor gene network.

CONCLUSIONS

The CIK phenotype, that is CD45RA(+), CCR7(-), CD62L-weakly positive, CD11a(+), CD27(+), CD28(-), macrophage inflammatory protein 1alpha(+), perforin(+), Fas ligand(+) coincides almost exactly with that described for the T RA(+) effector memory CD27 single positive subset of terminally differentiated human memory T cells.

Cellular and molecular mechanisms of memory T-cell survival

Long-term maintenance of the memory T-cell response is the hallmark of immune protection and, hence, constitutes one of the most important objectives of vaccine-development strategies. Persistent memory T cells, developed after vaccination or microbial infections, ensure the generation of an antimicrobial response upon re-exposure to the pathogen through rapid clonal proliferation and activation of effector functions. However, in the context of many pathogen infections, these memory T cells fail to persist and die. In this review, we will highlight recent exciting findings in studies of memory T cells, their generation, their lineage relationships and their survival pathways; indeed, survival of memory T cells and maintenance of their functionality are key features of the immune response in its quest to control disease progression and in the development of vaccines to persistent microbial infections.

Isopentenyl pyrophosphate-activated CD56+ {gamma}{delta} T lymphocytes display potent antitumor activity toward human squamous cell carcinoma

PURPOSE

The expression of CD56, a natural killer cell-associated molecule, on alphabeta T lymphocytes correlates with their increased antitumor effector function. CD56 is also expressed on a subset of gammadelta T cells. However, antitumor effector functions of CD56(+) gammadelta T cells are poorly characterized.

EXPERIMENTAL DESIGN

To investigate the potential effector role of CD56(+) gammadelta T cells in tumor killing, we used isopentenyl pyrophosphate and interleukin-2-expanded gammadelta T cells from peripheral blood mononuclear cells of healthy donors.

RESULTS

Thirty to 70% of expanded gammadelta T cells express CD56 on their surface. Interestingly, although both CD56(+) and CD56(-) gammadelta T cells express comparable levels of receptors involved in the regulation of gammadelta T-cell cytotoxicity (e.g., NKG2D and CD94), only CD56(+) gammadelta T lymphocytes are capable of killing squamous cell carcinoma and other solid tumor cell lines. This effect is likely mediated by the enhanced release of cytolytic granules because CD56(+) gammadelta T lymphocytes expressed higher levels of CD107a compared with CD56(-) controls following exposure to tumor cell lines. Lysis of tumor cell lines is blocked by concanamycin A and a combination of anti-gammadelta T-cell receptor + anti-NKG2D monoclonal antibody, suggesting that the lytic activity of CD56(+) gammadelta T cells involves the perforin-granzyme pathway and is mainly gammadelta T-cell receptor/NKG2D dependent. Importantly, CD56-expressing gammadelta T lymphocytes are resistant to Fas ligand and chemically induced apoptosis.

CONCLUSIONS

Our data indicate that CD56(+) gammadelta T cells are potent antitumor effectors capable of killing squamous cell carcinoma and may play an important therapeutic role in patients with head and neck cancer and other malignancies.

Relative quantification of canine CD56 mRNA expression by real-time polymerase chain reaction method in normal tissues and activated lymphocytes

Real-time PCR was optimized for the quantification of canine CD56 mRNA expression. This study was conducted to easily quantify canine CD56 expression and to identify its expression in normal tissues, peripheral blood mononuclear cells and activated lymphocytes in dogs. This assay revealed the highest level of CD56 mRNA expression in the normal canine brain, followed by the lung, kidney and liver. CD56 mRNA expression level in peripheral blood mononuclear cells was considerably lower; among activated lymphocytes in vitro, CD56 mRNA expression was increased.

Induction of CD56 and TCR-independent activation of T cells with aging

Degeneration of the thymus and severe contraction of the T cell repertoire with aging suggest that immune homeostasis in old age could be mediated by distinct effectors. Therefore, receptors expressed on T cells as they undergo senescence in vitro, as well as those displayed by circulating T cells during normal chronologic aging, were examined. Monitoring of T cells driven to senescence showed de novo induction of CD56, the prototypic receptor of NK cells. Analysis of fresh T cells in peripheral blood showed an age-dependent induction of CD56. These unusual T cells expressed high levels of Bcl2, p16, and p53, and had limited, or completely lost, ability to undergo cell division, properties consistent with senescence. CD56 cross-linking without TCR ligation on CD56(+) T cells resulted in extensive protein phosphorylation, NF-kappaB activation, and Bax down-regulation. CD56 cross-linking was also sufficient to drive production of various humoral factors. These data suggest that the immunologic environment in old age is functionally distinct, rather than being a dysfunctional version of that seen at a young age. CD56(+) T cells are unique effectors capable of mediating TCR-independent immune cascades that could be harnessed to enhance protective immunity in the elderly.