Human peripheral CD2−/lo T cells: an extrathymic population of early differentiated, developing T cells

Advances in CAR-T-cell therapy in T-cell malignancies

Significant advances have been made in chimeric antigen receptor T (CAR-T)-cell therapy for the treatment of recurrent or refractory B-cell hematologic malignancies. However, CAR-T-cell therapy has not yet achieved comparable success in the management of aggressive T-cell malignancies. This article reviews the challenges of CAR-T-cell therapy in treating T-cell malignancies and summarizes the progress of preclinical and clinical studies in this area. We present an analysis of clinical trials of CAR-T-cell therapies for the treatment of T-cell malignancies grouped by target antigen classification. Moreover, this review focuses on the major challenges encountered by CAR-T-cell therapies, including the nonspecific killing due to T-cell target antigen sharing and contamination with cell products during preparation. This review discusses strategies to overcome these challenges, presenting novel therapeutic approaches that could enhance the efficacy and applicability of CAR-T-cell therapy in the treatment of T-cell malignancies. These ideas and strategies provide important information for future studies to promote the further development and application of CAR-T-cell therapy in this field.

An "off-the-shelf" CD2 universal CAR-T therapy for T-cell malignancies

T-cell malignancies are associated with frequent relapse and high morbidity, which is partly due to the lack of effective or targeted treatment options. To broaden the use of CAR-T cells in pan T-cell malignancies, we developed an allogeneic "universal" CD2-targeting CAR-T cell (UCART2), in which the CD2 antigen is deleted to prevent fratricide, and the T-cell receptor is removed to prevent GvHD. UCART2 demonstrated efficacy against T-ALL and CTCL and prolonged the survival of tumor-engrafted NSG mice in vivo. To evaluate the impact of CD2 on CAR-T function, we generated CD19 CAR-T cells (UCART19) with or without CD2 deletion, single-cell secretome analysis revealed that CD2 deletion in UCART19 reduced frequencies of the effector cytokines (Granzyme-B and IFN-γ). We also observed that UCART19ΔCD2 had reduced anti-tumor efficacy compared to UCART19 in a CD19+NALM6 xenograft model. Of note is that the reduced efficacy resulting from CD2 deletion was reversed when combined with rhIL-7-hyFc, a long-acting recombinant human interleukin-7. Treatment with rhIL-7-hyFc prolonged UCART2 persistence and increased survival in both the tumor re-challenge model and primary patient T-ALL model in vivo. Together, these data suggest that allogeneic fratricide-resistant UCART2, in combination with rhIL-7-hyFc, could be a suitable approach for treating T-cell malignancies.

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.

Normal or reactive minor cell populations in bone marrow and peripheral blood mimic minimal residual leukemia by flow cytometry

BACKGROUND

Measurable residual disease (MRD) is a strong independent poor prognostic factor for acute leukemia. Multiparameter flow cytometry (FCM) is a commonly used MRD detection method. However, FCM MRD detection is not well standardized, and the interpretation is subjective. There are normal/reactive minor cell populations in bone marrow (BM) and peripheral blood (PB), which could be confused with MRD.

METHODS

The FCM data of 231 BM and 44 PB pediatric samples performed in a recent 15-month period were retrospectively reviewed. These samples were from 56 B-lymphoblastic leukemia (B-ALL) patients, 11 T-lymphoblastic leukemia (T-ALL) patients, 28 acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) patients, 44 cytopenia/leukocytosis patients, and five patients with mycosis fungoides.

RESULTS

There were over 10 normal or reactive minor cell populations identified with certain phenotypes mimicking MRD of acute leukemia. These mimickers included CD19+ NK cells, CD22+ basophils, CD22+ dendritic cells (DCs), and plasma cells for B-ALL MRD; CD4/8 double-negative T cells, CD4/8 double-positive T cells, cytoplasmic CD3+ NK cells, CD2- T cells, CD7- T cells, CD5- gamma delta T cells, CD56+ NKT cells for T-ALL MRD; CD33+ NK cells, CD117+ NK cells, basophils, plasmacytoid DCs, non-classical monocytes, CD56+ and/or CD61+ monocytes for AML MRD.

CONCLUSIONS

These data confirm the presence of a variety of normal/reactive minor cell populations that could mimic MRD of acute leukemia by FCM. Recognizing these MRD mimickers is important for correct FCM MRD interpretation.

Expression of T-Bet, Eomesodermin, and GATA-3 Correlates With Distinct Phenotypes and Functional Properties in Porcine γδ T Cells

Unlike mice and humans, porcine γδ T cells represent a prominent subset of T cells in blood and secondary lymphatic organs. GATA-3, T-bet and Eomesodermin (Eomes) are transcription factors with crucial functions in T-cell development and functional differentiation, but their expression has not been investigated in porcine γδ T cells so far. We analyzed the expression of these transcription factors in γδ thymocytes, mature γδ T cells from blood, spleen, lymph nodes, and lung tissue as well as in vitro stimulated γδ T cells on the protein level by flow cytometry. GATA-3 was present in more than 80% of all γδ-thymocytes. Extra-thymic CD2⁻ γδ T cells expressed high levels of GATA-3 in all investigated organs and had a CD8α^−/dimCD27⁺perforin⁻ phenotype. T-bet expression was mainly found in a subset of CD2⁺ γδ T cells with an opposing CD8α^highCD27^dim/−perforin⁺ phenotype. Eomes⁺ γδ T cells were also found within CD2⁺ γδ T cells but were heterogeneous in regard to expression of CD8α, CD27, and perforin. Eomes⁺ γδ T cells frequently co-expressed T-bet and dominated in the spleen. During aging, CD2⁻GATA-3⁺ γδ T cells strongly prevailed in young pigs up to an age of about 2 years but declined in older animals where CD2⁺T-bet⁺ γδ T cells became more prominent. Despite high GATA-3 expression levels, IL-4 production could not be found in γδ T cells by intracellular cytokine staining. Experiments with sorted and ConA + IL-2 + IL-12 + IL-18-stimulated CD2⁻ γδ T cells showed that proliferating cells start expressing CD2 and T-bet, produce IFN-γ, but retain GATA-3 expression. In summary, our data suggest a role for GATA-3 in the development of γδ-thymocytes and in the function of peripheral CD2⁻CD8α^−/dimCD27⁺perforin⁻ γδ T cells. In contrast, T-bet expression appears to be restricted to terminal differentiation stages of CD2⁺ γδ T cells, frequently coinciding with perforin expression. The functional relevance of high GATA-3 expression levels in extra-thymic CD2⁻ γδ T cells awaits further clarification. However, their unique phenotype suggests that they represent a thymus-derived separate lineage of γδ T cells in the pig for which currently no direct counterpart in rodents or humans has been described.

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.

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.

CD56 marks an effector T cell subset in the human intestine

T cells are key mediators of intestinal immunity, and specific T cell subsets can have differing immunoregulatory roles in animal models of mucosal inflammation. In this study, we describe human CD56+ T cells as a morphologically distinct population expressing a mature, nonproliferative phenotype that is frequent in the gut. Enhanced potential for IFN-gamma and TNF synthesis suggested a proinflammatory function, and we directly demonstrate effector function mediated by direct T-T interaction with responder cells in vitro. CD56+ T cells from peripheral blood responded to the gut-related CD2 signal, and were necessary for effective CD2-mediated proliferation of peripheral blood CD56- T cells. Our findings associate CD56+ T cells with the intestinal immune compartment and suggest a putative effector function in human mucosal immunity.

Bovine CD2-/NKp46+ cells are fully functional natural killer cells with a high activation status

BACKGROUND

Natural killer (NK) cells in the cow have been elusive due to the lack of specific NK cell markers, and various criteria including a CD3-/CD2+ phenotype have been used to identify such cells. The recent characterization of the NK-specific NKp46 receptor has allowed a more precise definition of bovine NK cells. NK cells are known as a heterogeneous cell group, and we here report the first functional study of bovine NK cell subsets, based on the expression of CD2.

RESULTS

Bovine CD2- NK cells, a minor subset in blood, proliferated more rapidly in the presence of IL-2, dominating the cultures after a few days. Grown separately with IL-2, CD2- and CD2+ NK cell subsets did not change CD2 expression for at least two weeks. In blood, CD2- NK cells showed a higher expression of CD44 and CD25, consistent with a high activation status. A higher proportion of CD2- NK cells had intracellular interferon-gamma in the cytoplasm in response to IL-2 and IL-12 stimulation, and the CD2- subset secreted more interferon-gamma when cultured separately. Cytotoxic capacity was similar in both subsets, and both carried transcripts for the NK cell receptors KIR, CD16, CD94 and KLRJ. Ligation by one out of two tested anti-CD2 monoclonal antibodies could trigger interferon-gamma production from NK cells, but neither of them could alter cytotoxicity.

CONCLUSION

These results provide evidence that bovine CD2- as well as CD2+ cells of the NKp46+ phenotype are fully functional NK cells, the CD2- subset showing signs of being more activated in the circulation.