Chimeric antigen receptor-induced antigen loss protects CD5.CART cells from fratricide without compromising on-target cytotoxicity.

Chimeric antigen receptor T cells (CART) targeting lymphocyte antigens can induce T cell fratricide and require additional engineering to mitigate self-damage. We demonstrate that the expression of a chimeric antigen receptor (CAR) targeting CD5, a prominent pan-T cell antigen, induces rapid internalization and complete loss of the CD5 protein on T cells, protecting them from self-targeting. Notably, exposure of healthy and malignant T cells to CD5.CART cells induces similar internalization of CD5 on target cells, transiently shielding them from cytotoxicity. However, this protection is short-lived, as sustained activity of CD5.CART cells in patients with T cell malignancies results in full ablation of CD5+ T cells while sparing healthy T cells naturally lacking CD5. These results indicate that continuous downmodulation of the target antigen in CD5.CART cells produces effective fratricide resistance without undermining their on-target cytotoxicity.

The significance of T-BET-positive CD8 T-cells with diminished CD5 expression in Kikuchi-Fujimoto disease.

Kikuchi-Fujimoto disease (KFD), also known as histiocytic necrotizing lymphadenitis, is a rare condition characterized by benign localized lymphadenopathy and clinical symptoms such as fever, sore throat, odynophagia, and leukopenia. Though the etiology of KFD is unknown, this condition is similar to viral infection, including increased infiltration of activated plasmacytoid dendritic cells. KFD exhibits three histological phases that reflect its progression status: proliferative, necrotic, and xanthomatous lesions. The expression loss of pan T-cell markers, such as CD2, CD5, and CD7, of infiltrating T-cells is observed in KFD cases, complicating the distinction from T-cell lymphoma. However, reports on the loss of their expression in KFD have been limited. Furthermore, the precise population of the T-cell subset in KFD is still unclear. Here, we focused on surface markers and transcription factors for T-cell differentiation and analyzed them immunohistochemically in 46 KFD cases. We observed diminished CD5 expression of CD8-positive (CD5dim CD8+) T-cells in the proliferative lesion of KFD cases. Furthermore, these CD5dim CD8+ T-cells expressed T-BET, a master regulator of type 1 helper T-cells. The upregulation of T-BET and downregulation of CD5 in CD8+ T-cells causes dysregulated activation and proliferation of CD8+ T-cells, potentially contributing to the unique histopathological features of KFD. Recognizing the frequent infiltration of T-BET-positive CD5dim CD8+ T-cells in KFD is important for distinguishing it from mature T-cell lymphoma. Our findings suggest that the immune response in KFD shares similarities with viral infections and highlight the importance of characterizing T-BET-positive CD5dim CD8+ T-cell populations for understanding KFD pathogenesis.

Early reappearance of intraclonal proliferative subpopulations in ibrutinib-resistant chronic lymphocytic leukemia.

The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib represents an effective strategy for treatment of chronic lymphocytic leukemia (CLL), nevertheless about 30% of patients eventually undergo disease progression. Here we investigated by flow cytometry the long-term modulation of the CLL CXCR4dim/CD5bright proliferative fraction (PF), its correlation with therapeutic outcome and emergence of ibrutinib resistance. By longitudinal tracking, the PF, initially suppressed by ibrutinib, reappeared upon early disease progression, without association with lymphocyte count or serum beta-2-microglobulin. Somatic mutations of BTK/PLCG2, detected in 57% of progressing cases, were significantly enriched in PF with a 3-fold greater allele frequency than the non-PF fraction, suggesting a BTK/PLCG2-mutated reservoir resident within the proliferative compartments. PF increase was also present in BTK/PLCG2-unmutated cases at progression, indicating that PF evaluation could represent a marker of CLL progression under ibrutinib. Furthermore, we evidence different transcriptomic profiles of PF at progression in cases with or without BTK/PLCG2 mutations, suggestive of a reactivation of B-cell receptor signaling or the emergence of bypass signaling through MYC and/or Toll-Like-Receptor-9. Clinically, longitudinal monitoring of the CXCR4dim/CD5bright PF by flow cytometry may provide a simple tool helping to intercept CLL progression under ibrutinib therapy.

[Clinical Features and Prognosis of Patients with CD5+ Diffuse Large B-Cell Lymphoma].

OBJECTIVE: To analyze the clinical characteristics and prognosis of patients with CD5+ diffuse large B-cell lymphoma (DLBCL). METHODS: The clinical data of 161 newly treated DLBCL patients in Gansu Provincial Hospital from January 2013 to January 2020 were retrospectively analyzed. According to CD5 expression, the patients were divided into CD5+ group and CD5- group. The clinical characteristics and prognosis of the two groups were statistically analyzed. RESULTS: The median age of patients in CD5+ group was 62 years, which was higher than 56 years in CD5- group (P =0.048). The proportion of women in CD5+ group was 62.96%, which was significantly higher than 41.79% in CD5- group (P =0.043). The proportion of patients with IPI score > 2 in CD5+ group was 62.96%, which was higher than 40.30% in CD5- group (P =0.031). Survival analysis showed that the median overall survival and progression-free survival time of patients in CD5+ group were 27(3-77) and 31(3-76) months, respectively, which were both shorter than 30(5-84) and 32.5(4-83) months in CD5- group (P =0.047, P =0.026). Univariate analysis showed that advanced age, positive CD5 expression, triple or double hit at initial diagnosis, high IPI score and no use of rituximab during chemotherapy were risk factors for the prognosis of DLBCL patients. Further Cox multivariate regression analysis showed that these factors were also independent risk factors except for advanced age. CONCLUSION: CD5+ DLBCL patients have a worse prognosis than CD5- DLBCL patients. Such patients are more common in females, with advanced age and high IPI score, which is a special subtype of DLBCL.

Identification of CD5/SOX11 double-negative pleomorphic mantle cell lymphoma.

Cyclin D1 protein-positive diffuse large B cell lymphoma (DLBCL) has an immunophenotype of CD5(-) cyclin D1(+) SOX11(-), and most cases lack a CCND1 rearrangement and have a gene expression profile of DLBCL. Rarely, cyclin D1 protein-positive DLBCL harbors a CCND1 rearrangement, and some genetic copy number features typical of mantle cell lymphoma (MCL) have been detected. Since gene expression studies have not been performed, whether such CCND1-rearranged cases represent cyclin D1 protein-positive DLBCL or CD5/SOX11 double-negative pleomorphic MCL remains unclear. To date, no cases of CD5/SOX11 double-negative MCL have been reported. In this study, we collected eight cases initially diagnosed as cyclin D1 protein-positive DLBCL, including four with a CCND1 rearrangement and four without. Immunohistochemically, all four CCND1-rearranged cases had >50% of tumor cells positive for cyclin D1 protein, whereas only one (25%) non-rearranged case had >50% positive tumor cells. Analysis of genome-wide copy number, mutational, and gene expression profiles revealed that CCND1-rearranged cases were similar to MCL, whereas CCND1-non-rearranged cases resembled DLBCL. Despite the SOX11 negativity by immunohistochemistry, CCND1-rearranged cases had a notable trend (P = 0.064) of higher SOX11 mRNA levels compared to non-rearranged cases. Here, we show for the first time that CCND1 rearrangement could be useful for identifying CD5/SOX11 double-negative pleomorphic MCL in cases diagnosed as cyclin D1 protein-positive DLBCL. Cases with >50% cyclin D1 protein-positive tumor cells immunohistochemically and higher SOX11 mRNA levels are more likely to have a CCND1 rearrangement, and fluorescence in situ hybridization can be used to detect the rearrangement.

Benzo[a]pyrene exposure causes exonal switch resulting in reduced surface CD5 expression in an AHR-dependent manner.

The function of CD5 protein in T cells is well documented, but regulation of its surface-level expression has yet to be fully understood. However, variation in its surface expression is associated with various immunopathological conditions and haematological malignancies. Briefly, expression of an alternate exon E1B of a human endogenous retroviruses (HERV) origin directly downregulates the conventional transcript variant (E1A), as its expression leads to the retention of the resultant protein at the intracellular level (cCD5). A separate promoter governs the expression of E1B and may be influenced by different transcription factors. Hence, we performed in silico transcription factor binding site (TFBS) analysis of the 3 kb upstream region from TSS of exon E1B and found five putative DREs (Dioxin Response elements) with good similarity scores. Further, we observed the upregulation in E1B expression after the exposure of BaP (a dioxin) and the reduction of E1A expression and their respective protein, i.e. sCD5 and cCD5. The binding of AHR at the predicted DRE sites was confirmed by ChIP qPCR and AHR specific inhibitor and gene silencing studies suggested the involvement of AHR in exonal switch. This study indicates that the polycyclic aromatic hydrocarbon decreases the sCD5 expression by upregulating alternative exon expression, which may adversely affect the overall T cell functions.

[Salivary carcinoma showing thymus-like differentiation: clinicopathological analysis of 7 cases].

Objective: To analyze the clinicopathological features of salivary carcinoma showing thymus-like differentiation(CASTLE). Methods: Cases diagnosed with salivary CASTLE from January 2020 to December 2023 were collected and selected from the Department of Oral Pathology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine. A total of 7 cases of salivary CASTLE were identified. All the cases originated from parotid. There were 3 males and 4 females. The patients' age range was 11-70 years.The clinical, microscopic, immunohistochemical and prognostic features of these cases were analyzed. Results: The duration of disease ranged from 1 month to 1 year, and 1 patient had facial numbness and 1 with swelling sensation occasionally. Radiographically, 4 cases showed malignant signs. Microscopically, 4 cases involved in parotid gland, and all the tumors had different degrees of lymphoid tissue background. The tumor cells arranged in nests, 5 cases with lymphoepithelial carcinoma-like and 2 cases with squamous cell carcinoma morphology. The tumor cells expressed CD5 and CD117 proteins diffusely in lymphoepithelial carcinoma-like cases. However, the tumor cells expressed CD5 diffusely and CD117 focally in cases with squamous cell carcinoma morphology. All the cases had no Epstein-Barr virus infection. Among the 6 patients with follow-up information, all of them underwent postoperative radiotherapy, and none of them had local recurrence and lymph node metastasis. Conclusions: Salivary CASTLE is a rare tumor, it should be distinguished from lymphoepithelial carcinoma and squamous cell carcinoma. The patients often have better prognosis and CD5 protein expression has a valuable role in the differential diagnosis.

CD5 expression by dendritic cells directs T cell immunity and sustains immunotherapy responses.

The induction of proinflammatory T cells by dendritic cell (DC) subtypes is critical for antitumor responses and effective immune checkpoint blockade (ICB) therapy. Here, we show that human CD1c+CD5+ DCs are reduced in melanoma-affected lymph nodes, with CD5 expression on DCs correlating with patient survival. Activating CD5 on DCs enhanced T cell priming and improved survival after ICB therapy. CD5+ DC numbers increased during ICB therapy, and low interleukin-6 (IL-6) concentrations promoted their de novo differentiation. Mechanistically, CD5 expression by DCs was required to generate optimally protective CD5hi T helper and CD8+ T cells; further, deletion of CD5 from T cells dampened tumor elimination in response to ICB therapy in vivo. Thus, CD5+ DCs are an essential component of optimal ICB therapy.

CD5-Negative Primary Mantle Cell Lymphoma Presenting with a Bilateral Conjunctival Mass: A Potential Diagnostic Pitfall.

Mantle cell lymphoma is a B-cell malignancy, which, in its classic form, usually involves lymph nodes and extranodal sites, and, among the extranodal sites, the gastrointestinal tract and the Waldeyer's ring are most prevalent. MCL is rarely reported in the ocular adnexa, a site more frequently affected by extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, which is a form of low-grade malignancy. The diagnosis of MCL presenting in the ocular adnexa requires special attention as its rarity in this location combined with the not uncommon CD5 negativity of the disease when occurring in the ocular adnexa, may lead the pathologist to overlook the diagnosis and misinterpret MCL as marginal zone B cell lymphoma, which has a totally different behavior. Herein, we present a case of primary bilateral conjunctival CD5-negative MCL in a patient having no other sites affected by lymphoma and we discuss possible diagnostic pitfalls.

Human coagulation factor X and CD5 antigen-like are potential new members of the zonulin family proteins.

Zonulin is a physiologic epithelial and endothelial permeability modulator. Zonulin increases antigen trafficking from the gut lumen into the bloodstream and in between body compartments, a mechanism linked to many chronic inflammatory diseases. Upon its initial discovery, it was noted that zonulin was not a single protein, but rather a family of structurally and functionally related proteins referred to as the zonulin family proteins (ZFPs). ZFPs are members of the mannose associated serine proteases (MASP) family and are the result of high mutation rates leading to many zonulin polymorphisms. Pre-haptoglobin 2, the precursor of haptoglobin 2, was identified as the first eukaryotic member of the ZFPs, and properdin, a key positive regulator of the alternative pathway, as a second member. In this study, we report two additional proteins that are likely ZFPs. Human coagulation factor X (FX) and CD5 antigen-like (CD5L). Both FX and CD5L recombinant proteins were detected by anti-zonulin antibody in Western immunoblot analysis, and both proteins decreased epithelial barrier competency of Caco-2 cell monolayers as established by the Trans Epithelial Electrical Resistance (TEER) assay. These results indicate that FX and CD5L have structural and functional similarities with previously identified ZFPs and, therefore, can be considered new members of this family of proteins.

Signal inhibitory receptor on leukocytes-1 regulates the formation of the neutrophil extracellular trap in rheumatoid arthritis.

BACKGROUND: Neutrophil extracellular trap (NET) has been demonstrated to play important roles in the pathogenesis and progression of rheumatoid arthritis (RA). Emerging evidence indicates that ligation of signal inhibitory receptor on leukocytes-1 (SIRL-1) can dampen Fc receptor-induced reactive oxygen species (ROS) production in primary human neutrophils by reducing extracellular signal-regulated kinase (ERK) activation. The current study aimed to determine the regulatory effects of SIRL-1 on the NET formation and ROS production by comparing RA patients and healthy controls (HC). METHODS: Multiple assays were employed to detect the expression level of SIRL-1, including immunohistochemical staining, quantitative reverse transcription polymerase chain reaction (RT-PCR) and flow cytometry. Peripheral blood neutrophils from both HC and RA patients were freshly isolated. The NET formation was assessed spontaneously before and after exposure to serum samples from HC and RA patients, respectively. The quantification of NET formation was determined by fluorescence microscopy and Spectra Max M5 fluorescent plate reader. The ROS production was examined by flow cytometry. RESULTS: The expression level of SIRL-1 in peripheral blood neutrophils was decreased in RA, comparing to HC. The RA-originated neutrophils showed higher levels of ROS production and NET formation. Ligation of SIRL-1 to neutrophils suppressed ROS production and NET formation. Stimulation of neutrophils with severe anti-cyclic citrullinated peptides (CCP) induced NET formation, which could be inhibited by application of SIRL-1 ligation. CONCLUSION: The current study identified SIRL-1 differentially expressed in neutrophils between RA and HC. Ligation of SIRL-1 inhibited ROS production and NET formation. Downregulation of SIRL-1 showed correlation with upregulation of NET formation in RA. These findings showed the regulation of SIRL-1 on NET formation and provided a potential therapeutic target for RA.

CD5+ diffuse large B-cell lymphoma has heterogeneous clinical features and poor prognosis: a single-center retrospective study in China.

OBJECTIVE: De novo CD5-positive (CD5+) diffuse large B-cell lymphoma (DLBCL) has different clinical characteristics compared with CD5-negative (CD5-) DLBCL. However, few studies have been reported in Chinese cohorts. We investigated the clinical features and prognosis of patients with CD5+ DLBCL and summarized the related literature. METHODS: Data from 245 patients with newly diagnosed DLBCL were retrospectively assessed. RESULTS: Thirty-one and 214 patients were diagnosed with CD5+ DLBCL or CD5- DLBCL, respectively. In the CD5+ DLBCL group, there were significantly higher proportions of patients with older age (≥60 years), International Prognostic Index (IPI) ≥3, Eastern Cooperative Oncology Group (ECOG) scores ≥ 2, bone marrow involvement, positive B-cell lymphoma 2 expression, and positive MYC expression. Survival analysis showed that CD5+ DLBCL had a markedly poorer 2-year progression-free survival than CD5- DLBCL (18.2% vs. 56.2%). Univariate analysis indicated that age ≥60 years, ECOG score ≥ 2, IPI ≥ 3, B symptoms, and no rituximab-based treatment were poor predictive factors for overall survival (OS). Multivariate analysis revealed that B symptoms and no rituximab-based treatment, but not positive CD5 expression, were independent factors for OS. CONCLUSIONS: Patients with CD5+ DLBCL had heterogeneous clinical characteristics and poor survival. The development of more targeted and effective therapies is needed.

CD5 Suppresses IL-15-Induced Proliferation of Human Memory CD8+ T Cells by Inhibiting mTOR Pathways.

IL-15 induces the proliferation of memory CD8+ T cells as well as NK cells. The expression of CD5 inversely correlates with the IL-15 responsiveness of human memory CD8+ T cells. However, whether CD5 directly regulates IL-15-induced proliferation of human memory CD8+ T cells is unknown. In the current study, we demonstrate that human memory CD8+ T cells in advanced stages of differentiation respond to IL-15 better than human memory CD8+ T cells in stages of less differentiation. We also found that the expression level of CD5 is the best correlate for IL-15 hyporesponsiveness among human memory CD8+ T cells. Importantly, we found that IL-15-induced proliferation of human memory CD8+ T cells is significantly enhanced by blocking CD5 with Abs or knocking down CD5 expression using small interfering RNA, indicating that CD5 directly suppresses the IL-15-induced proliferation of human memory CD8+ T cells. We also found that CD5 inhibits activation of the mTOR pathway, which is required for IL-15-induced proliferation of human memory CD8+ T cells. Taken together, the results indicate that CD5 is not just a correlative marker for IL-15 hyporesponsiveness, but it also directly suppresses IL-15-induced proliferation of human memory CD8+ T cells by inhibiting mTOR pathways.

A Case of CD5-Positive Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type Secondary to Chronic Lymphedema.

ABSTRACT: Primary cutaneous lymphoma occurring at the site of lymphedema is a rare complication. A total of 13 cases of primary cutaneous lymphoma associated with chronic lymphedema have been reported in international studies. We reported a case of cutaneous diffuse large B-cell lymphoma (DLBCL) (leg type) secondary to chronic lymphedema of the lower limbs. Histopathology showed hyperkeratosis of epidermis, acanthosis, and significant edema in the superficial dermis, with diffuse mononuclear infiltration in the dermis. Immunohistochemical studies revealed the expression of CD5, CD20, Pax-5, Bcl-2, Bcl-6, MUM-1, c-myc, and Ki-67. Therefore, the diagnosis of cutaneous DLBCL (leg type) was made. The study further confirmed the association between lymphoma and lymphedema. Especially, it showed CD5 expression. CD5-positive DLBCLs is a specific subgroup of DLBCLs, only approximately 10% of DLBCLs express CD5.

B cell depletion with anti-CD20 mAb exacerbates anti-donor CD4+ T cell responses in highly sensitized transplant recipients.

Pretransplant desensitization with rituximab has been applied to preformed donor-specific anti-human leukocyte antigen antibody (DSA)-positive recipients for elimination of preformed DSA. We investigated the impact of pretransplant desensitization with rituximab on anti-donor T cell responses in DSA-positive transplant recipients. To monitor the patients' immune status, mixed lymphocyte reaction (MLR) assays were performed before and after desensitization with rituximab. Two weeks after rituximab administration, the stimulation index (SI) of anti-donor CD4+ T cells was significantly higher in the DSA-positive recipients than in the DSA-negative recipients. To investigate the mechanisms of anti-donor hyper responses of CD4+ T cells after B cell depletion, highly sensitized mice models were injected with anti-CD20 mAb to eliminate B cells. Consistent with clinical observations, the SI values of anti-donor CD4+ T cells were significantly increased after anti-CD20 mAb injection in the sensitized mice models. Adding B cells isolated from untreated sensitized mice to MLR significantly inhibited the enhancement of anti-donor CD4+ T cell response. The depletion of the CD5+ B cell subset, which exclusively included IL-10-positive cells, from the additive B cells abrogated such inhibitory effects. These findings demonstrate that IL-10+ CD5+ B cells suppress the excessive response of anti-donor CD4+ T cells responses in sensitized recipients.

CD5+ diffuse large B-cell lymphoma: a narrative review.

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous entity, and cell surface cluster of differentiation (CD) 5 expression may represent a distinct subset. Here, we provide a narrative review of CD5+ DLBCL to understand its clinical implications. Between 5-10% of DLBCL express CD5, making it an uncommon subset. Studies have variably shown that CD5+ DLBCL may be associated with increased age, high lactate dehydrogenase, B symptoms, extra-nodal sites, higher International Prognostic Index score, and advanced stage. CD5+ DLBCLs are more likely to express Bcl-2, MYC, and MUM1; a large proportion exhibit an activated B-cell (ABC)-like phenotype. The balance of studies generally supports an independent prognostic value of CD5 in DLBCL While more aggressive first-line regimens have been advocated for CD5+ DLBCL, including dose-adjusted R-EPOCH and autologous stem cell transplant, evidence to support these approaches is lacking; further study is warranted to identify the optimal treatment strategy for this disease entity.

Expression Level of Membrane Markers CD5, CD19, and CD20 in B Cells after UV-Irradiation and Incubation in the Presence of Autologous Plasma.

The effect of UV-light (240-390 nm) in doses of 151 and 755 J/m2 on the expression of membrane markers CD5, CD19, CD20 in human peripheral blood B cells was studied by flow cytometry. In 24 h after exposure to UV light, we observed activation of processes accompanied by structural rearrangements of B-cell membranes leading to changes in the expression of receptor molecules: the content of of CD19 and CD20 increased due to activation of the synthesis of these proteins, while the content of CD5 decreased. The percentage of CD5+ cells decreased over 24 h after UV-irradiation of lymphocytes, while addition of autologous plasma to the incubation medium produced a photoprotective effect on CD5+ cells.