Establishment of a vascular endothelial cell-reactive type II NKT cell clone from a rat model of autoimmune vasculitis

The role of natural killer T cells in liver transplantation

Natural killer T cells (NKTs) are innate-like lymphocytes that are abundant in the liver and participate in liver immunity. NKT cells express both NK cell and T cell markers, modulate innate and adaptive immune responses. Type I and Type II NKT cells are classified according to the TCR usage, while they recognize lipid antigen in a non-classical major histocompatibility (MHC) molecule CD1d-restricted manner. Once activated, NKT cells can quickly produce cytokines and chemokines to negatively or positively regulate the immune responses, depending on the different NKT subsets. In liver transplantation (LTx), the immune reactions in a series of processes determine the recipients' long-term survival, including ischemia-reperfusion injury, alloresponse, and post-transplant infection. This review provides insight into the research on NKT cells subpopulations in LTx immunity during different processes, and discusses the shortcomings of the current research on NKT cells. Additionally, the CD56-expressing T cells are recognized as a NK-like T cell population, they were also discussed during these processes.

The ratio of CD163-positive macrophages to Iba1-positive macrophages is low in the intima in the early stage of cutaneous arteritis

The etiology of polyarteritis nodosa (PAN) and localized PAN, including cutaneous arteritis (CA), remains unknown; however, initial endothelial damage has been implicated. The intima of the vasculitis lesions is predominantly infiltrated by innate-like bystander-activated CD8 T cells, in addition to the macrophages. Macrophages are among the major inflammatory cells involved in innate immunity and are classified into M1 and M2 subtypes. M1-type macrophages kill pathogens and cause inflammation, while M2-type macrophages promote the repair of tissues. Macrophage subtypes infiltrating in PAN and localized PAN vasculitis lesions have not yet been investigated. Innate immune response to a triggering factor on the endothelial cell surface may initiate CA pathogenesis. Thus, many M1-type macrophages may infiltrate in the intima during early CA. We assessed this hypothesis by immunohistochemical observation of macrophage phenotypes and polarization. Twenty-seven skin biopsy specimens from patients with CA were retrieved. Based on histology, we classified CA into four phases. The phenotypes of infiltrating macrophages in CA were evaluated by immunohistochemistry using antibodies against Iba-1, a pan-macrophage marker, and CD163, an M2-type macrophage marker. Our results showed that the ratio of CD163-positive M2-type macrophages to Iba1-positive macrophages was lower in the intima in the early stage of CA than in the later stage. In the media to adventitia, there was no significant difference in the ratios between these stages. These findings indicate that innate immunity is involved in the intima in the early stage of CA, suggesting that a trigger for CA might exist in endothelial cells.

Type II NKT Cell Agonist, Sulfatide, Is an Effective Adjuvant for Oral Heat-Killed Cholera Vaccines

Oral vaccination has the potential to offer a safer and more efficacious approach for protection against enteric pathogens than injection-based approaches, especially in developing countries. One key advantage is the potential to induce intestinal immune responses in addition to systemic immunity. In general, antigen delivery via the oral route triggers weak immune responses or immunological tolerance. The effectiveness of oral vaccination can be improved by co-administering adjuvants. However, a major challenge is the absence of potent and safe oral adjuvants for clinical application. Here, the Type II NKT cell activator sulfatide is shown for the first time to be an effective oral adjuvant for Vibrio cholerae vaccine antigens in a mouse model. Specifically, administration of sulfatide with the oral cholera vaccine Dukoral^® resulted in enhancement of intestinal antigen-specific IgA in addition to Th1 and Th17 immune responses. In summary, sulfatide is a promising adjuvant for inclusion in an oral cholera vaccine and our data further support the potential of adjuvants targeting NKT cells in new vaccine strategies.

Flip-flops of natural killer cells in autoimmune diseases versus cancers: Immunologic axis

Natural killer (NK) cells play an essential role in the immune response to infections, inflammations, and malignancies. Recent studies suggest that NK cell surface receptors and cytokines are the key points of the disease development and protection. We hypothesized that the interactions between NK cell receptors and targeted cells construct an eventual niche, and this niche has an eventual profile in various autoimmune diseases and cancers. The NK cells preactivated with cytokines, such as interleukin-2 (IL-2), IL-12, IL-15, and IL-18 can have higher cytotoxicity; however, the toxic side effect of IL-2 should be considered. The vicissitudes of NK cell profile and its receptors obey the environmental communications and cell interactions. Our vision around the NK cells as an immune axis remained dual, and we still cannot judge the immune responses based on the NK cell flip-flop. A design of eventual niche to monitor the NK cell and targeted cell interaction is needed to strengthen our ability in diagnosis and treatment approaches based on the NK cells. Here, we have reviewed the shifts in the NK cells and their surface receptors in autoimmune diseases, solid tumors, and leukemia, and also discussed the effective chemokines that affect NK cell activation and proliferation. The main aim of this review is to present a broader vision of the NK cell changes in autoimmune disease and cancers.

The Role of CD1d and MR1 Restricted T Cells in the Liver

The liver is one of the most important immunological organs that remains tolerogenic in homeostasis yet promotes rapid responses to pathogens in the presence of a systemic infection. The composition of leucocytes in the liver is highly distinct from that of the blood and other lymphoid organs, particularly with respect to enrichment of innate T cells, i.e., invariant NKT cells (iNKT cells) and Mucosal-Associated Invariant T cells (MAIT cells). In recent years, studies have revealed insights into their biology and potential roles in maintaining the immune-environment in the liver. As the primary liver-resident immune cells, they are emerging as significant players in the human immune system and are associated with an increasing number of clinical diseases. As such, innate T cells are promising targets for modifying host defense and inflammation of various liver diseases, including viral, autoimmune, and those of tumor origin. In this review, we emphasize and discuss some of the recent discoveries and advances in the biology of innate T cells, their recruitment and diversity in the liver, and their role in various liver diseases, postulating on their potential application in immunotherapy.

Detection of Autoreactive Type II NKT Cells: A Pilot Study of Comparison Between Healthy Individuals and Patients with Vasculitis

NKT cells are defined as T cells that recognize hydrophobic antigens presented by class I MHC-like molecules, including CD1d. Among CD1d-restricted NKT cells, type I and type II subsets have been noted. CD1d-restricted type I NKT cells are regarded as pro-inflammatory cells in general. On the contrary, accumulated evidence has demonstrated an anti-inflammatory property of CD1d-restricted type II NKT cells. In our earlier study using a rat model with vasculitis, we demonstrated the pro-inflammatory function of CD1d-restricted type II NKT cells and identified that one such cell recognized P_518-532 of rat sterol carrier protein 2 (rSCP2_518-532 ), which appeared on vascular endothelial cells presented by CD1d. Based on this evidence, we attempted to detect human CD1d-restricted type II NKT cells in peripheral blood using hSCP2_518-532 , the human counterpart of rSCP2_518-532, together with a CD1d tetramer in flow cytometry. First, we determined the binding of hSCP2_518-532 to CD1d. Next, we detected CD3-positive hSCP2_518-532 -loaded CD1d (hSCP2_518-532 /CD1d) tetramer-binding cells in peripheral blood of healthy donors. The abundance of TGF-β-producing cells rather than TNF-α-producing cells in CD3-positive hSCP2_518-532 /CD1d tetramer-binding cells suggests the anti-inflammatory property of SCP2-loaded CD1d (SCP2/CD1d) tetramer-binding type II NKT cells in healthy individuals. Furthermore, we compared cytokine profile between healthy individuals and patients with vasculitis in a pilot study. Interestingly, the percentage of TGF-β-producing cells in SCP2/CD1d tetramer-binding type II NKT cells in vasculitic patients was significantly lower than that in healthy controls despite the greater number of these cells. Although further studies to clarify the mechanism and significance of this phenomenon are needed, SCP2/CD1d tetramer-binding type II NKT cells in peripheral blood should be examined in more detail to understand the pathophysiology of vasculitides in humans. © 2018 International Society for Advancement of Cytometry.

CD1d-Restricted Type II NKT Cells Reactive With Endogenous Hydrophobic Peptides

NKT cells belong to a distinct subset of T cells that recognize hydrophobic antigens presented by major histocompatibility complex class I-like molecules, such as CD1d. Because NKT cells stimulated by antigens can activate or suppress other immunocompetent cells through an immediate production of a large amount of cytokines, they are regarded as immunological modulators. CD1d-restricted NKT cells are classified into two subsets, namely, type I and type II. CD1d-restricted type I NKT cells express invariant T cell receptors (TCRs) and react with lipid antigens, including the marine sponge-derived glycolipid α-galactosylceramide. On the contrary, CD1d-restricted type II NKT cells recognize a wide variety of antigens, including glycolipids, phospholipids, and hydrophobic peptides, by their diverse TCRs. In this review, we focus particularly on CD1d-restricted type II NKT cells that recognize endogenous hydrophobic peptides presented by CD1d. Previous studies have demonstrated that CD1d-restricted type I NKT cells usually act as pro-inflammatory cells but sometimes behave as anti-inflammatory cells. It has been also demonstrated that CD1d-restricted type II NKT cells play opposite roles to CD1d-restricted type I NKT cells; thus, they function as anti-inflammatory or pro-inflammatory cells depending on the situation. In line with this, CD1d-restricted type II NKT cells that recognize type II collagen peptide have been demonstrated to act as anti-inflammatory cells in diverse inflammation-induction models in mice, whereas pro-inflammatory CD1d-restricted type II NKT cells reactive with sterol carrier protein 2 peptide have been demonstrated to be involved in the development of small vessel vasculitis in rats.

In vasculitis of small muscular arteries, activation of vessel-infiltrating CD8 T cells seems to be antigen-independent

The etiology of polyarteritis nodosa (PAN) and localized PAN is still unknown, although a T cell-mediated immune mechanism has been considered. CD8 T cells participate not only in the antigen-dependent adaptive immune system, but also in the antigen-independent innate immune system. Non-antigen-activated CD8 T cells express a unique phenotype: granzyme B (GrB) positive /CD25 negative /programmed death-1 (PD-1) negative. The aims of this study were to assess the participation of T cells, especially innate CD8 T cells, in the development of vasculitis. Twenty-eight consecutive cases of skin biopsy specimens with cutaneous vasculitis of small muscular arteries (CVSMA) were retrieved. The series comprises of 21 cases of cutaneous arteritis, three cases of PAN, and four cases of rheumatoid vasculitis. Cases of antineutrophil cytoplasmic antibody-associated vasculitis were excluded. The phenotypes of infiltrating lymphocytes in vasculitis lesions were evaluated by immunohistochemistry. In most cases of CVSMA, the number of CD8 T cells infiltrating the intima was higher than that of CD4 T cells, and significant numbers of GrB-positive cells, which represent activated CD8 T cells, were observed. However, GrB/CD25-double-positive cells, which correspond to antigen-activated T cells, were very few in a small number of cases. Cells positive for PD-1, which is also expressed on antigen-activated CD8 T cells, were not detected. We conclude that a T cell-mediated immune mechanism, involving cytotoxic CD8 T cells, may play a role in the development of CVSMA. Low expression of CD25 in activated CD8 T cells suggests that activation was antigen-independent.

Type II Natural Killer T Cells that Recognize Sterol Carrier Protein 2 Are Implicated in Vascular Inflammation in the Rat Model of Systemic Connective Tissue Diseases

We previously generated a rat model that developed systemic connective tissue diseases, including synovitis, myositis, and small-vessel vasculitis (SVV), and established a vascular endothelial cell-reactive T-cell clone, VASC-1, from the model. VASC-1 was determined to be a type II natural killer T-cell clone. In this study, we attempted to identify the antigen recognized by VASC-1. The monkey-derived cell line COS-7 was used because VASC-1 does not bind naturally to COS-7, although the amino acid sequences are well conserved between monkey CD1d and rat CD1d. We generated 98 COS-7 clones transfected with miscellaneous rat cDNA and screened them for VASC-1 binding. Consequently, we found one clone, 4D2, which could bind to VASC-1. Sequencing identified the rat cDNA introduced into 4D2 as sterol carrier protein 2 (SCP2). When VASC-1 was co-cultured with SCP2 knockdown rat vascular endothelial cells, VASC-1 binding was reduced significantly. Moreover, we designed a series of rat SCP2 peptides and introduced them into COS-7 cells. On the basis of VASC-1 binding and proliferation, we revealed that the peptide rSCP2_518-532 included the epitope recognized by VASC-1. Furthermore, immunization with rSCP2_518-532 accelerated the development of SVV in the rat model. The collective findings suggest that type II natural killer T cells reactive with autologous SCP2 are implicated in vascular inflammation in the rat model.