Trogocytosis between Non-Immune Cells for Cell Clearance, and among Immune-Related Cells for Modulating Immune Responses and Autoimmunity

Trichomonas gallinae Kills Host Cells Using Trogocytosis

Trichomonas gallinae (T. gallinae) is an infectious parasite that is prevalent worldwide in poultry and can cause death in both poultry and wild birds. Although studies have shown that T. gallinae damages host cells through direct contact, the mechanism is still unclear. In this study, we found that T. gallinae can kill host cells by ingesting fragments of the host cells, that is, by trogocytosis. Moreover, we found that the PI3K inhibitor wortmannin and the cysteine protease inhibitor E-64D prevented T. gallinae from destroying host cells. To the best of our knowledge, our study has demonstrated for the first time that T. gallinae uses trogocytosis to kill host cells. Understanding this mechanism is crucial for the prevention and control of avian trichomoniasis and will contribute to the development of vaccines and drugs for the prevention and control of avian trichomoniasis.

Trogocytosis in innate immunity to cancer is an intimate relationship with unexpected outcomes

Trogocytosis is a cellular process whereby a cell acquires a membrane fragment from a donor cell in a contact-dependent manner allowing for the transfer of surface proteins with functional integrity. It is involved in various biological processes, including cell-cell communication, immune regulation, and response to pathogens and cancer cells, with poorly defined molecular mechanisms. With the exception of eosinophils, trogocytosis has been reported in most immune cells and plays diverse roles in the modulation of anti-tumor immune responses. Here, we report that eosinophils acquire membrane fragments from tumor cells early after contact through the CD11b/CD18 integrin complex. We discuss the impact of trogocytosis in innate immune cells on cancer progression in the context of the evidence that eosinophils can engage in trogocytosis with tumor cells. We also discuss shared and cell-specific mechanisms underlying this process based on in silico modeling and provide a hypothetical molecular model for the stabilization of the immunological synapse operating in granulocytes and possibly other innate immune cells that enables trogocytosis.

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Trogocytosis in innate immune cells can regulate immune responses to cancer

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Eosinophils engage in trogocytosis with tumor cells via CD11b/CD18 integrin complex

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CD11b/CD18 integrin, focal adhesion molecules and actin network enable trogocytosis

Molecular Basis for Paradoxical Activities of Polymorphonuclear Neutrophils in Inflammation/Anti-Inflammation, Bactericide/Autoimmunity, Pro-Cancer/Anticancer, and Antiviral Infection/SARS-CoV-II-Induced Immunothrombotic Dysregulation

Polymorphonuclear neutrophils (PMNs) are the most abundant white blood cells in the circulation. These cells act as the fast and powerful defenders against environmental pathogenic microbes to protect the body. In addition, these innate inflammatory cells can produce a number of cytokines/chemokines/growth factors for actively participating in the immune network and immune homeostasis. Many novel biological functions including mitogen-induced cell-mediated cytotoxicity (MICC) and antibody-dependent cell-mediated cytotoxicity (ADCC), exocytosis of microvesicles (ectosomes and exosomes), trogocytosis (plasma membrane exchange) and release of neutrophil extracellular traps (NETs) have been successively discovered. Furthermore, recent investigations unveiled that PMNs act as a double-edged sword to exhibit paradoxical activities on pro-inflammation/anti-inflammation, antibacteria/autoimmunity, pro-cancer/anticancer, antiviral infection/COVID-19-induced immunothrombotic dysregulation. The NETs released from PMNs are believed to play a pivotal role in these paradoxical activities, especially in the cytokine storm and immunothrombotic dysregulation in the recent SARS-CoV-2 pandemic. In this review, we would like to discuss in detail the molecular basis for these strange activities of PMNs.

Colon cancer cells acquire immune regulatory molecules from tumor-infiltrating lymphocytes by trogocytosis

Cancer cells can develop an immunosuppressive tumor microenvironment to control tumor-infiltrating lymphocytes. The underlying mechanisms still remain unclear. Here, we report that mouse and human colon cancer cells acquire lymphocyte membrane proteins including cellular markers such as CD4 and CD45. We observed cell populations harboring both a tumor-specific marker and CD4 in the tumor microenvironment. Sorted cells from these populations were capable of forming organoids, identifying them as cancer cells. Live imaging analysis revealed that lymphocyte membrane proteins were transferred to cancer cells via trogocytosis. As a result of the transfer in vivo, cancer cells also acquired immune regulatory surface proteins such as CTLA4 and Tim3, which suppress activation of immune cells [T. L. Walunas et al, Immunity 1, 405-413 (1994) and L. Monney et al., Nature 415, 536-541 (2002)]. RNA sequencing analysis of ex vivo-cocultured splenocytes with trogocytic cancer cells showed reductions in Th1 activation and natural killer cell signaling pathways compared with the nontrogocytic control. Cancer cell trogocytosis was confirmed in the patient-derived xenograft models of colorectal cancer and head and neck cancer. These findings suggest that cancer cells utilize membrane proteins expressed in lymphocytes, which in turn contribute to the development of the immunosuppressive tumor microenvironment.

The Role of Trogocytosis in the Modulation of Immune Cell Functions

Trogocytosis is an active process, in which one cell extracts the cell fragment from another cell, leading to the transfer of cell surface molecules, together with membrane fragments. Recent reports have revealed that trogocytosis can modulate various biological responses, including adaptive and innate immune responses and homeostatic responses. Trogocytosis is evolutionally conserved from protozoan parasites to eukaryotic cells. In some cases, trogocytosis results in cell death, which is utilized as a mechanism for antibody-dependent cytotoxicity (ADCC). In other cases, trogocytosis-mediated intercellular protein transfer leads to both the acquisition of novel functions in recipient cells and the loss of cellular functions in donor cells. Trogocytosis in immune cells is typically mediated by receptor–ligand interactions, including TCR–MHC interactions and Fcγ receptor-antibody-bound molecule interactions. Additionally, trogocytosis mediates the transfer of MHC molecules to various immune and non-immune cells, which confers antigen-presenting activity on non-professional antigen-presenting cells. In this review, we summarize the recent advances in our understanding of the role of trogocytosis in immune modulation.

Shaping of T Cell Functions by Trogocytosis

Trogocytosis is an active process whereby plasma membrane proteins are transferred from one cell to the other cell in a cell-cell contact-dependent manner. Since the discovery of the intercellular transfer of major histocompatibility complex (MHC) molecules in the 1970s, trogocytosis of MHC molecules between various immune cells has been frequently observed. For instance, antigen-presenting cells (APCs) acquire MHC class I (MHCI) from allografts, tumors, and virally infected cells, and these APCs are subsequently able to prime CD8⁺ T cells without antigen processing via the preformed antigen-MHCI complexes, in a process called cross-dressing. T cells also acquire MHC molecules from APCs or other target cells via the immunological synapse formed at the cell-cell contact area, and this phenomenon impacts T cell activation. Compared with naïve and effector T cells, T regulatory cells have increased trogocytosis activity in order to remove MHC class II and costimulatory molecules from APCs, resulting in the induction of tolerance. Accumulating evidence suggests that trogocytosis shapes T cell functions in cancer, transplantation, and during microbial infections. In this review, we focus on T cell trogocytosis and the related inflammatory diseases.