The B8.2C12 monoclonal antibody reacts with mouse TIM-3 (T cell immunoglobulin and mucin domain-3) also known as CD366. This antibody binds to the BALB/c allele of TIM-3 while reactivity to the C57Bl/6 allele is significantly weaker. TIM-3 is a 60 kDa member of the TIM family of immune checkpoint receptors and exists as a type I transmembrane glycoprotein with a mucin-like domain in its extracellular portion and a tyrosine phosphorylation motif in its cytoplasmic portion. TIM-3 is specifically expressed at high levels on the surface of Th1 lymphocytes whereas Th2 lymphocytes express TIM-1 and TIM-2. TIM-3 activation occurs via binding to the cell-associated C-type lectin galectin-9. Upon binding TIM-3 induces apoptosis of Th1 cells. Inhibition of TIM-3 signaling in mice has been shown to exacerbate experimental autoimmune encephalomyelitis, promote IFNγ production and Th1 cell proliferation. Tim-3 has also been shown to be required for the induction of tolerance, as both TIM-3 knockout animals and mice treated with TIM-3-Ig fusion protein display defects in the induction of antigen-specific tolerance. Additionally, TIM-3 signaling is currently being explored as a cancer immunotherapy target as CD8 T cells which express both TIM-3 and PD-1 exhibit greater defects in both cell-cycle progression and effector cytokine production than cells that express PD-1 alone.

INVIVOMAB ANTI-MOUSE TIM-3 (CD366) (CLONE: B8.2C12)

Wang, H. W., et al. (2015). “Microglia activity modulated by T cell Ig and mucin domain protein 3 (Tim-3).” Cell Immunol 293(1): 49-58. PubMed

Microglia are the main innate immune cells in the central nervous system that are actively involved in maintaining brain homeostasis and diseases. T cell Ig and mucin domain protein 3 (Tim-3) plays critical roles in both the adaptive and the innate immune system and is an emerging therapeutic target for treatment of various disorders. In the brain Tim-3 is specifically expressed on microglia but its functional role is unclear. Here, we showed that Tim-3 was up-regulated on microglia by ATP or LPS stimulation. Tim-3 activation with antibodies increased microglia expression of TGF-beta, TNF-alpha and IL-1beta. Blocking of Tim-3 with antibodies decreased the microglial phagocytosis of apoptotic neurons. Tim-3 blocking alleviated the detrimental effect of microglia on neurons and promoted NG2 cell differentiation in co-cultures. Finally, MAPKs namely ERK1/2 and JNK proteins were phosphorylated upon Tim-3 activation in microglia. Data indicated that Tim-3 modulates microglia activity and regulates the interaction of microglia-neural cells.

Hongo, D., et al. (2014). “Requirement for interactions of natural killer T cells and myeloid-derived suppressor cells for transplantation tolerance.” Am J Transplant 14(11): 2467-2477. PubMed

The goal of the study was to elucidate the cellular and molecular mechanisms by which a clinically applicable immune tolerance regimen of combined bone marrow and heart transplants in mice results in mixed chimerism and graft acceptance. The conditioning regimen of lymphoid irradiation and anti-T cell antibodies changed the balance of cells in the lymphoid tissues to create a tolerogenic microenvironment favoring the increase of natural killer T (NKT) cells, CD4+ CD25+ regulatory T cells and Gr-1+ CD11b+ myeloid-derived suppressor cells (MDSCs), over conventional T cells (Tcons). The depletion of MDSCs abrogated chimerism and tolerance, and add back of these purified cells was restorative. The conditioning regimen activated the MDSCs as judged by the increased expression of arginase-1, IL-4Ralpha and programmed death ligand 1, and the activated cells gained the capacity to suppress the proliferation of Tcons to alloantigens in the mixed leukocyte reaction. MDSC activation was dependent on the presence of host invariant NKT cells. The conditioning regimen polarized the host invariant NKT cells toward IL-4 secretion, and MDSC activation was dependent on IL-4. In conclusion, there was a requirement for MDSCs for chimerism and tolerance, and their suppressive function was dependent on their interactions with NKT cells and IL-4.

Hou, H., et al. (2014). “Tim-3 negatively mediates natural killer cell function in LPS-induced endotoxic shock.” PLoS One 9(10): e110585. PubMed

Sepsis is an exaggerated inflammatory condition response to different microorganisms with high mortality rates and extremely poor prognosis. Natural killer (NK) cells have been reported to be the major producers of IFN-gamma and key players in promoting systematic inflammation in lipopolysaccharide (LPS)-induced endotoxic shock. T-cell immunoglobulin and mucin domain (Tim)-3 pathway has been demonstrated to play an important role in the process of sepsis, however, the effect of Tim-3 on NK cell function remains largely unknown. In this study, we observed a dynamic inverse correlation between Tim-3 expression and IFN-gamma production in NK cells from LPS-induced septic mice. Blockade of the Tim-3 pathway could increase IFN-gamma production and decrease apoptosis of NK cells in vitro, but had no effect on the expression of CD107a. Furthermore, NK cell cytotoxicity against K562 target cells was enhanced after blocking Tim-3 pathway. In conclusion, our results suggest that Tim-3 pathway plays an inhibitory role in NK cell function, which might be a potential target in modulating the excessive inflammatory response of LPS-induced endotoxic shock.

Chabtini, L., et al. (2013). “TIM-3 regulates innate immune cells to induce fetomaternal tolerance.” J Immunol 190(1): 88-96. PubMed

TIM-3 is constitutively expressed on subsets of macrophages and dendritic cells. Its expression on other cells of the innate immune system and its role in fetomaternal tolerance has not yet been explored. In this study, we investigate the role of TIM-3-expressing innate immune cells in the regulation of tolerance at the fetomaternal interface (FMI) using an allogeneic mouse model of pregnancy. Blockade of TIM-3 results in accumulation of inflammatory granulocytes and macrophages at the uteroplacental interface and upregulation of proinflammatory cytokines. Furthermore, TIM-3 blockade inhibits the phagocytic potential of uterine macrophages resulting in a build up of apoptotic bodies at the uteroplacental interface that elicits a local immune response. In response to inflammatory cytokines, Ly-6C(hi)G(neg) monocytic myeloid-derived suppressor cells expressing inducible NO synthase and arginase 1 are induced. However, these suppressive cells fail to downregulate the inflammatory cascade induced by inflammatory granulocytes (Ly-6C(int)G(hi)) and apoptotic cells; the increased production of IFN-gamma and TNF-alpha by inflammatory granulocytes leads to abrogation of tolerance at the FMI and fetal rejection. These data highlight the interplay between cells of the innate immune system at the FMI and their influence on successful pregnancy in mice.

Hongo, D., et al. (2012). “Interactions between NKT cells and Tregs are required for tolerance to combined bone marrow and organ transplants.” Blood 119(6): 1581-1589. PubMed

We used a model of combined bone marrow and heart transplantation, in which tolerance and stable chimerism is induced after conditioning with fractionated irradiation of the lymphoid tissues and anti-T-cell antibodies. Graft acceptance and chimerism required host CD4(+)CD25(+) Treg production of IL-10 that was in-turn enhanced by host invariant natural killer (NK) T-cell production of IL-4. Up-regulation of PD-1 on host Tregs, CD4(+)CD25(-) conventional T (Tcon) cells, and CD8(+) T cells was also enhanced by NKT cell production of IL-4. Up-regulated PD-1 expression on Tregs was linked to IL-10 secretion, on CD8(+) T cells was linked to Tim-3 expression, and on CD4(+) Tcon cells was associated with reduced IFNgamma secretion. Changes in the expression of PD-1 were induced by the conditioning regimen, and declined after bone marrow transplantation. In conclusion, NKT cells in this model promoted changes in expression of negative costimulatory receptors and anti-inflammatory cytokines by Tregs and other T-cell subsets in an IL-4-dependent manner that resulted in tolerance to the bone marrow and organ grafts.

Wang, F., et al. (2009). “Tim-3-Galectin-9 pathway involves the suppression induced by CD4+CD25+ regulatory T cells.” Immunobiology 214(5): 342-349. PubMed

CD4(+)CD25(+) regulatory T cells (Tregs) are considered to play a key role as suppressors of immune-mediated reactions. The mechanisms of this suppression in animals and patients with autoimmune, allergic or oncogenic diseases have been investigated under various conditions. However, the precise mode of suppression by CD4(+)CD25(+) Tregs is still not clear. In this report, Tim-3-Galectin-9 pathway was explored as one of the mechanisms for the suppression and cytotoxicity induced by Tregs. Here, we demonstrated that Galectin-9 was expressed on CD4(+)CD25(+) Tregs by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Interestingly, blocking Tim-3-Galectin-9 pathway resulted in an obvious decreased suppression activity of Tregs and enhanced Th1 cytokine level in vitro. Furthermore, blocking Tim-3-Galectin-9 pathway negated prolonged survival of allogeneic skin grafts induced by CD4(+)CD25(+) Tregs in vivo. Our results suggest that Tim-3-Galectin-9 pathway involves the function of CD4(+)CD25(+) Tregs.

Nakae, S., et al. (2007). “TIM-1 and TIM-3 enhancement of Th2 cytokine production by mast cells.” Blood 110(7): 2565-2568. PubMed

Members of the T-cell immunoglobulin- and mucin-domain-containing molecule (TIM) family have roles in T-cell-mediated immune responses. TIM-1 and TIM-2 are predominantly expressed on T helper type 2 (Th2) cells, whereas TIM-3 is preferentially expressed on Th1 and Th17 cells. We found that TIM-1 and TIM-3, but neither TIM-2 nor TIM-4, were constitutively expressed on mouse peritoneal mast cells and bone marrow-derived cultured mast cells (BMCMCs). After IgE + Ag stimulation, TIM-1 expression was down-regulated on BMCMCs, whereas TIM-3 expression was up-regulated. We also found that recombinant mouse TIM-4 (rmTIM-4), which is a ligand for TIM-1, as well as an anti-TIM-3 polyclonal Ab, can promote interleukin-4 (IL-4), IL-6, and IL-13 production without enhancing degranulation in BMCMCs stimulated with IgE + Ag. Moreover, the anti-TIM-3 Ab, but neither anti-TIM-1 Ab nor rmTIM-4, suppressed mast-cell apoptosis. These observations suggest that TIM-1 and TIM-3 may be able to influence T-cell-mediated immune responses in part through effects on mast cells.

Frisancho-Kiss, S., et al. (2006). “Cutting edge: T cell Ig mucin-3 reduces inflammatory heart disease by increasing CTLA-4 during innate immunity.” J Immunol 176(11): 6411-6415. PubMed

Autoimmune diseases can be reduced or even prevented if proinflammatory immune responses are appropriately down-regulated. Receptors (such as CTLA-4), cytokines (such as TGF-beta), and specialized cells (such as CD4+CD25+ T regulatory cells) work together to keep immune responses in check. T cell Ig mucin (Tim) family proteins are key regulators of inflammation, providing an inhibitory signal that dampens proinflammatory responses and thereby reducing autoimmune and allergic responses. We show in this study that reducing Tim-3 signaling during the innate immune response to viral infection in BALB/c mice reduces CD80 costimulatory molecule expression on mast cells and macrophages and reduces innate CTLA-4 levels in CD4+ T cells, resulting in decreased T regulatory cell populations and increased inflammatory heart disease. These results indicate that regulation of inflammation in the heart begins during innate immunity and that Tim-3 signaling on cells of the innate immune system critically influences regulation of the adaptive immune response.

Monney, L., et al. (2002). “Th1-specific cell surface protein Tim-3 regulates macrophage activation and severity of an autoimmune disease.” Nature 415(6871): 536-541. PubMed

Activation of naive CD4(+) T-helper cells results in the development of at least two distinct effector populations, Th1 and Th2 cells. Th1 cells produce cytokines (interferon (IFN)-gamma, interleukin (IL)-2, tumour-necrosis factor (TNF)-alpha and lymphotoxin) that are commonly associated with cell-mediated immune responses against intracellular pathogens, delayed-type hypersensitivity reactions, and induction of organ-specific autoimmune diseases. Th2 cells produce cytokines (IL-4, IL-10 and IL-13) that are crucial for control of extracellular helminthic infections and promote atopic and allergic diseases. Although much is known about the functions of these two subsets of T-helper cells, there are few known surface molecules that distinguish between them. We report here the identification and characterization of a transmembrane protein, Tim-3, which contains an immunoglobulin and a mucin-like domain and is expressed on differentiated Th1 cells. In vivo administration of antibody to Tim-3 enhances the clinical and pathological severity of experimental autoimmune encephalomyelitis (EAE), a Th1-dependent autoimmune disease, and increases the number and activation level of macrophages. Tim-3 may have an important role in the induction of autoimmune diseases by regulating macrophage activation and/or function.