Antibodies selected from combinatorial libraries block a tumor antigen that plays a key role in immunomodulation

Dendritic cell subpopulations in carcinoma ex-pleomorphic adenoma: A multicenter study

OBJECTIVE

Carcinoma ex-pleomorphic adenoma (CEXPA) represents a malignant transformation from a recurrent or primary pleomorphic adenoma (PA), and the immune response may be essential in this process. Therefore, in this study, we aimed to identify and quantify subpopulations of dendritic cells (DCs) in CEXPA, residual PA in CEXPA (rPA), and PA.

MATERIALS AND METHODS

A multicenter study was performed collecting salivary gland tumor (SGT) samples from three Oral and Maxillofacial Pathology Centers. A tissue microarray containing 41 samples of CEXPA and 22 samples of PA was included in this study and submitted to immunohistochemical reactions against CD1a, CD83, CD207, and Ki67 antibodies.

RESULTS

Both PA and rPA showed a higher quantification of CD207+ and CD83+ cells when compared to CEXPA (p < 0.001 and p < 0.01, respectively). There was also a difference when comparing the cell proliferation index between PA/rPA and CEXPA using the Ki-67 marker (p = 0.043). However, there was no difference in the DC population regarding clinical parameters such as sex, anatomical location, size, and metastases (p > 0.06).

CONCLUSIONS

Immunohistochemical profile of DC subpopulations and cell proliferation biomarkers in SGTs can contribute as an important tool in the differentiation of benign and malignant tumors or detection of initial areas with malignant transformation.

Targeting Histone 3 Variants Epigenetic Landscape and Inhibitory Immune Checkpoints: An Option for Paediatric Brain Tumours Therapy

Despite little progress in survival rates with regular therapies, which do not provide complete care for curing pediatric brain tumors (PBTs), there is an urgent need for novel strategies to overcome the toxic effects of conventional therapies to treat PBTs. The co-inhibitory immune checkpoint molecules, e.g., CTLA-4, PD-1/PD-L1, etc., and epigenetic alterations in histone variants, e.g., H3K27me3 that help in immune evasion at tumor microenvironment have not gained much attention in PBTs treatment. However, key epigenetic mechanistic alterations, such as acetylation, methylation, phosphorylation, sumoylation, poly (ADP)-ribosylation, and ubiquitination in histone protein, are greatly acknowledged. The crucial checkpoints in pediatric brain tumors are cytotoxic T lymphocyte antigen-4 (CTLA-4), programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PDL1), OX-2 membrane glycoprotein (CD200), and indoleamine 2,3-dioxygenase (IDO). This review covers the state of knowledge on the role of multiple co-inhibitory immunological checkpoint proteins and histone epigenetic alterations in different cancers. We further discuss the processes behind these checkpoints, cell signalling, the current scenario of clinical and preclinical research and potential futuristic opportunities for immunotherapies in the treatment of pediatric brain tumors. Conclusively, this article further discusses the possibilities of these interventions to be used for better therapy options.

Leishmania antigens activated CD4+ T cells expressing CD200R receptors are the prime IL-10 producing phenotype and an important determinant of visceral leishmaniasis pathogenesis

The excessive production of IL-10, an anti-inflammatory cytokine, by Leishmania antigen-activated T cells is supposed to be a key player in the onset and progression of visceral leishmaniasis (VL). The IL-10-producing sources in VL remain unidentified and uncharacterized. In this study, we reveal that antigen-activated CD4+ T cells, i.e., CD44+CD4+ T cells expressing CD200R receptors, are the prime IL-10-producing phenotypes in Leishmania donovani infection-induced pathogenesis. These phenotypes are separate from CD25+Foxp3+CD4+ T regulatory cells, which are classical IL-10-producing phenotypes. In order to ascertain the role of CD200R and CD25 receptors in IL-10 overexpression-associated VL pathogenesis, we abrogated CD200R and CD25 receptor-mediated signaling in the infected mice. The splenic load of parasites and the size of the liver and spleen were significantly reduced in CD200-blocked mice as compared to CD25-blocked mice. Further, the CD200 blocking polarized CD4+ T cells to pro-inflammatory cytokines-producing phenotypes, as we observed a higher frequency of IFN-γ, TNF-α, and IL-12 positive cells as compared to controls including the CD25 blocking. Our findings suggest that in L. donovani infection-induced pathogenesis the expression of CD200R on antigen-activated T cells helps them to acquire IL-10-producing abilities as part of its one of the survival strategies. However, more studies would be warranted to better understand CD200R receptors role in VL pathogenesis and to develop the next generation of therapeutic and prophylactic control measures.

Evaluation of Diagnostic Usefulness of CD200 Expression in B-cell Chronic Lymphoproliferative Disorders

Immunophenotyping by flow cytometry (FCM) is a useful diagnostic tool for the evaluation of mature B-cell neoplasms (MBN). Here, CD200 expression may play a significant role and improve the distinction between various MBNs, but any potential as a prognostic marker is yet to be established. The present prospective study was conducted on all the suspected cases of MBNs. Immunophenotyping was done using a BD FACS Canto FCM using a panel of 4 to 6 color combinations of monoclonal antibodies; CD45, CD34, CD5, CD19, CD20, CD22, CD23, CD79b, FMC7, CD10, CD38, ZAP70, CD200, IgG, IgM, CD25, CD103, CD2, CD3, CD11c as well as κ and λ light chains. CD200 expression was compared in different subgroups. Of the total of 130 cases included in the study, CD200 was positive in 118 cases (90%). CD200 was expressed in 100% of the cases of CLL(86 cases), atypical CLL(06 cases), HCL(14 cases), FL(02 cases), SMZL(04 cases), LPL (01 case), and low-grade NHL (05 cases), with the highest intensity of fluorescence in HCL followed by CLL. All the cases of MCL and PLL were exclusively negative for CD200. In conclusion, the results of the present study support inclusion of this marker in the flow cytometric panels for the differential diagnosis of MBNs.

The Use of CD200 in the Differential Diagnosis of B-Cell Lymphoproliferative Disorders

Background: B-Cell Lymphoproliferative Disorders (B-LPDs) are a group of heterogenous disorders characterised by the accumulation of B-cells in peripheral blood, bone marrow, lymph nodes and spleen. They have a variable disease course and outcome and many share similar features making differential diagnosis challenging. Therefore, accurate diagnosis is fundamental in particular for determining treatment options. Immunophenotyping by flow cytometry plays a crucial role in the diagnosis of B-LPDs. However, overlapping immunophenotyping patterns exist and the use of novel monoclonal antibodies has become increasingly important in immunophenotyping analysis. More recently differential expression of CD200 has been reported in various B-LPDs and that CD200 may improve the differentiation between chronic lymphocytic leukaemia (CLL) and mantle cell lymphoma (MCL). In this study CD200 expression is evaluated in different B-LPDs. Methods: A total of 100 samples were collected and analysed by immunophenotyping flow cytometry over a period of 1 year (2017-2018), by a panel of monoclonal antibodies including CD200. The percentage of CD200 and its expression intensity was evaluated and compared between different groups of B-LPDs. Results: All of the 50 cases of CLL expressed CD200 with moderate to bright intensity, 6 MCL cases lacked the expression of CD200. Furthermore, all 5 cases of hairy cell leukaemia (HCL) expressed CD200. Out of all B-LPDs evaluated, CD200 expression in HCL cases was noted to be the brightest. The other 39 cases were not found to be B-LPDs. Conclusion: CD200 has an important role in differentiating CLL from MCL, HCL has a consistent bright expression of CD200. By adding CD200 to the combinations of markers in routine testing panel, Immunophenotyping by flow cytometry can be an effective tool in the diagnosis of B-LPDs especially in cases with atypical immunophenotyping pattern. Our result support that CD200 can be added to routine testing panel as it is useful in differentiating them.

Recombinant antibodies by phage display for bioanalytical applications

Antibody phage display, aimed at preparing antibodies to defined antigens, is a useful replacement for hybridoma technology. The phage system replaces all work stages that follow animal immunization with simple procedures for manipulating DNA and bacteria. It enables the time needed to generate stable antibody-producing clones to be shortened considerably, making the process noticeably cheaper. Antibodies prepared by phage display undergo several affinity selection steps and can be used as selective receptors in biosensors. This article briefly describes the techniques used in the making of phage antibodies to various antigens. The possibilities and prospects are discussed of using phage antibodies as selective agents in analytical systems, including biosensors.

The immunoregulatory protein CD200 as a potentially lucrative yet elusive target for cancer therapy

CD200 is an immunoregulatory cell surface ligand with proven pro-tumorigenic credentials via its ability to suppress CD200 receptor (CD200R)-expressing anti-tumor immune function. This definitive role for the CD200-CD200R axis in regulating an immunosuppressive tumor microenvironment has garnered increasing interest in CD200 as a candidate target for immune checkpoint inhibition therapy. However, while the CD200 blocking antibody samalizumab is still in the early stages of clinical testing, alternative mechanisms for the pro-tumorigenic role of CD200 have recently emerged that extend beyond direct suppression of anti-tumor T cell responses and, as such, may not be susceptible to CD200 antibody blockade. Herein, we will summarize the current understanding of CD200 expression and function in the tumor microenvironment as well as alternative strategies for potential neutralization of multiple CD200 mechanisms in human cancers.

CD200 ectodomain shedding into the tumor microenvironment leads to NK cell dysfunction and apoptosis

The basis of immune evasion, a hallmark of cancer, can differ even when cancers arise from one cell type such as in the human skin keratinocyte carcinomas: basal and squamous cell carcinoma. Here we showed that the basal cell carcinoma tumor-initiating cell surface protein CD200, through ectodomain shedding, was responsible for the near absence of NK cells within the basal cell carcinoma tumor microenvironment. In situ, CD200 underwent ectodomain shedding by metalloproteinases MMP3 and MMP11, which released biologically active soluble CD200 into the basal cell carcinoma microenvironment. CD200 bound its cognate receptor on NK cells to suppress MAPK pathway signaling that in turn blocked indirect (IFN-γ release) and direct cell killing. In addition, reduced ERK phosphorylation relinquished negative regulation of PPARγ-regulated gene transcription and led to membrane accumulation of the Fas/FADD death receptor and its ligand, FasL, which resulted in activation-induced apoptosis. Blocking CD200 inhibition of MAPK or PPARγ signaling restored NK cell survival and tumor cell killing, with relevance to many cancer types. Our results thus uncover a paradigm for CD200 as a potentially novel and targetable NK cell-specific immune checkpoint, which is responsible for NK cell-associated poor outcomes in many cancers.

Single-Chain Fragment Variable: Recent Progress in Cancer Diagnosis and Therapy

Simple Summary

Recombinant antibody fragments have shown remarkable potential as diagnostic and therapeutic tools in the fight against cancer. The single-chain fragment variable (scFv) that contains the complete antigen-binding domains of a whole antibody, has several advantages such as a high specificity and affinity for antigens, a low immunogenicity, and the proven ability to penetrate tumor tissues and diffuse. This review provides an overview of the current studies on the principle, generation, and applications of scFvs, particularly in the diagnosis and therapy of cancer, and underscores their potential use in clinical trials.

Abstract

Cancer remains a public health problem worldwide. Although conventional therapies have led to some excellent outcomes, some patients fail to respond to treatment, they have few therapeutic alternatives and a poor survival prognosis. Several strategies have been proposed to overcome this issue. The most recent approach is immunotherapy, particularly the use of recombinant antibodies and their derivatives, such as the single-chain fragment variable (scFv) containing the complete antigen-binding domains of a whole antibody that successfully targets tumor cells. This review describes the recent progress made with scFvs as a cancer diagnostic and therapeutic tool, with an emphasis on preclinical approaches and their potential use in clinical trials.

CD200 Blockade Modulates Tumor Immune Microenvironment but Fails to Show Efficacy in Inhibiting Tumor Growth in a Murine Model of Melanoma

CD200-CD200R pathway regulates immune responses and has been implicated in the pathogenesis of a number of cancer types. CD200 blockade is considered a strategy for immunotherapy of CD200-positive cancers such as melanoma. Thus, it is critical to understand the potential impacts of CD200 blockade in a more human relevant tumor model. In this study, we evaluated these issues using the CD200⁺ Yumm1.7 mouse melanoma model. Yumm1.7 cells bear Braf/Pten mutations resembling human melanoma. We found that Yumm1.7 tumors grow significantly faster in CD200R^–/– mice compared to wild type mice. Analysis of tumor immune microenvironment (TIME) revealed that tumors from CD200R^–/– or anti-CD200 treated mice had downregulated immune cell contents and reduced TCR clonality compared to tumors from untreated wild type mice. T cells also showed impaired effector functions, as reflected by reduced numbers of IFN-γ⁺ and TNF-α⁺ T cells. Mechanistically, we found upregulation of the CCL8 gene in CD200R^–/– tumors. In vitro co-culture experiments using Yumm1.7 tumor cells with bone marrow derived macrophages (BMDM) from WT and CD200R^–/– mice confirmed upregulation of macrophage CCL8 in the absence of CD200-CD200R interaction. Finally, we found that anti-CD200 therapy failed to show efficacy either alone or in combination with checkpoint inhibitors such as anti-PD-1 or anti-CTLA4 in inhibiting Yumm1.7 tumor growth. Given that CD200R-deficiency or anti-CD200 treatment leads to reduced T cell responses in TME, using blockade of CD200 as an immunotherapy for cancers such as melanoma should be practiced with caution.

Signaling by the inhibitory receptor CD200R is rewired by type I interferon

CD200 receptor 1 (CD200R) is an inhibitory immunoreceptor that suppresses Toll-like receptor (TLR)–induced cytokine production through the adaptor protein Dok2 and the GTPase activating protein (GAP) p120-RasGAP, which can be cleaved during mild cellular stress. We found that in the presence of cleaved p120-RasGAP, CD200R lost its capacity to inhibit phosphorylation of ribosomal S6 protein (rpS6), suggesting the reduced activity of mammalian target of rapamycin complex 1 (mTORC1). Furthermore, treatment of human peripheral blood mononuclear cells (PBMC) with interferon-α (IFN-α) resulted in increased amounts of cleaved p120-RasGAP. Upon pretreatment of cells with increasing concentrations of IFN-α, CD200R switched from inhibiting to potentiating the TLR7- and TLR8-induced expression of the gene encoding IFN-γ, a cytokine that is important for innate and adaptive immunity and is implicated in systemic lupus erythematosus (SLE) pathogenesis. PBMC from patients with SLE, a prototypic type I IFN disease, had an increased abundance of cleaved p120-RasGAP compared to that in cells from healthy controls. In a subset of SLE patients, CD200R stopped functioning as an inhibitory receptor or potentiated TLR-induced IFNG mRNA expression. Thus, our data suggest that type I IFN rewires CD200R signaling to be proinflammatory, which could contribute to the perpetuation of inflammation in patients with SLE.

The CD200-CD200R axis promotes squamous cell carcinoma metastasis via regulation of cathepsin K

The CD200-CD200R immunoregulatory signaling axis plays an etiological role in the survival and spread of numerous cancers primarily through suppression of anti-tumor immune surveillance. Our previous work outlined a pro-metastatic role for the CD200-CD200R axis in cutaneous squamous cell carcinoma (cSCC) that is independent of direct T cell suppression but modulates the function of infiltrating myeloid cells. To identify effectors of the CD200-CD200R axis important for cSCC metastasis, we conducted RNA-Seq profiling of infiltrating CD11B+Cd200R+ cells isolated from CD200+ versus CD200-null cSCCs and identified the cysteine protease cathepsin K (Ctsk) to be highly upregulated in CD200+ cSCCs. CD11B+Cd200R+ cells expressed phenotypic markers associated with myeloid-derived suppressor cell-like cells and tumor-associated macrophages and were the primary source of Ctsk expression in cSCC. A Cd200R+ myeloid cell-cSCC co-culture system showed that induction of Ctsk was dependent on engagement of the CD200-CD200R axis, indicating that Ctsk is a target gene of this pathway in the cSCC tumor microenvironment. Inhibition of Ctsk, but not matrix metalloproteinases (MMP), significantly blocked cSCC cell migration in vitro. Finally, targeted CD200 disruption in tumor cells and Ctsk pharmacological inhibition significantly reduced cSCC metastasis in vivo. Collectively, these findings support the conclusion that CD200 stimulates cSCC invasion and metastasis via induction of Ctsk in CD200R+ infiltrating myeloid cells.

Identification of a novel conserved signaling motif in CD200 receptor required for its inhibitory function

The inhibitory signaling of CD200 receptor 1 (CD200R) has been attributed to its NPxY signaling motif. However, NPxY-motifs are present in multiple protein families and are mostly known to mediate protein trafficking between subcellular locations rather than signaling. Therefore, we investigated whether additional motifs specify the inhibitory function of CD200R. We performed phylogenetic analysis of the intracellular domain of CD200R in mammals, birds, bony fish, amphibians and reptiles. Indeed, the tyrosine of the NPxY-motif is fully conserved across species, in line with its central role in CD200R signaling. In contrast, P295 of the NPxY-motif is not conserved. Instead, a conserved stretch of negatively charged amino acids, EEDE279, and two conserved residues P285 and K292 in the flanking region prior to the NPxY-motif are required for CD200R mediated inhibition of p-Erk, p-Akt308, p-Akt473, p-rpS6 and LPS-induced IL-8 secretion. Altogether, we show that instead of the more common NPxY-motif, CD200R signaling can be assigned to a unique signaling motif in mammals defined by: EEDExxPYxxYxxKxNxxY.

CD200 and Chronic Lymphocytic Leukemia: Biological and Clinical Relevance

CD200, a transmembrane type Ia glycoprotein belonging to the immunoglobulin protein superfamily, is broadly expressed on a wide variety of cell types, such as B lymphocytes, a subset of T lymphocytes, dendritic cells, endothelial and neuronal cells. It delivers immunosuppressive signals through its receptor CD200R, which is expressed on monocytes/myeloid cells and T lymphocytes. Moreover, interaction of CD200 with CD200R has also been reported to play a role in the regulation of tumor immunity. Overexpression of CD200 has been reported in chronic lymphocytic leukemia (CLL) and hairy cell leukemia but not in mantle cell lymphoma, thus helping to better discriminate between these different B cell malignancies with different prognosis. In this review, we focus on the role of CD200 expression in the differential diagnosis of mature B-cell neoplasms and on the prognostic significance of CD200 expression in CLL, where conflicting results have been published so far. Of interest, increasing evidences indicate that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing malignancies, such as CLL.

Molecular Immunotherapy: Promising Approach to Treat Metastatic Colorectal Cancer by Targeting Resistant Cancer Cells or Cancer Stem Cells

The immune system is able to recognize and eliminate tumor cells. Some tumors, including colorectal cancer (CRC), induce immune tolerance via different mechanisms of “immunoediting” and “immune evasion” and can thus escape immune surveillance. The impact of immunotherapy on cancer has been investigated for many years, but so far, the application was limited to few cancer types. Immuno-oncological therapeutic strategies against metastatic colorectal cancer (mCRC), the adaptive immune system activating approaches, offer a high potential for adaptation to the great heterogeneity of CRC. Moreover, novel treatment approaches are currently being tested that might specifically target the disease initiating and maintaining population of colorectal cancer stem cells (CSCs). In this review, we aim to summarize the current state of immune-oncology and tumor immunotherapy of patients with mCRC and discuss different therapeutic modalities that focus on the activation of tumor-specific T-cells and their perspectives such as tumor vaccination, checkpoint inhibition, and adoptive T-cell transfer or on the eradication of colorectal CSCs.

Clinical significance of CD200 expression in newly diagnosed multiple myeloma patients and dynamic changing during treatment

The aim of our study was to determine the impact of CD200 expression in newly diagnosed myltiple myeloma (MM) patients. CD200⁺ patients had significantly shorter median overall survival time (OS) than CD200^- patients (41.0 months vs. not reached, p = .009). The ratio of CD4⁺ to CD8⁺ T cells was lower in CD200⁺ patients and this reduction was significantly related to the increase of CD8⁺ T cells (p = .021). Moreover, we analyzed dynamic changes of CD200 expression in 47 CD200⁺ patients during treatment. Thirty-eight (80.9%) patients switched to CD200^- during treatment. Those patients had a favorable survival compared with the others (median OS, 65.0 vs. 32.0 months, p < .001; median PFS, 29.0 vs. 11.5 months, p = .027). We concluded that CD200 expression is an independent marker for MM prognostic estimation during treatment.

CD200 is overexpressed in neuroblastoma and regulates tumor immune microenvironment

Patients with pediatric cancers such as neuroblastoma (NB) are often unresponsive to checkpoint blockade immunotherapy. One major factor in pediatric tumor resistance to immunotherapy is considered to be the low mutation rate of pediatric tumors. Another factor may be the overexpression of additional inhibitory pathways. While analyzing the RNA-sequencing database TARGET, we found that human NB tumors overexpress immune checkpoint molecule CD200. To determine its significance and impact on tumor immune microenvironment, we analyzed 49 cases of previously untreated, surgically removed NB tumors using immunohistochemistry and multi-color flow cytometry (FACS). We found that CD200 is overexpressed in more than 90% of NB tumors. In the tumor microenvironment of NB, CD200 is mainly overexpressed in CD45^- NB tumor cells, while its cognate receptor (CD200R) is mainly expressed in HLA-DR⁺CD14⁺ myeloid cells and CD11c⁺ dendritic cells. Low-level expression of CD200R is also observed in tumor-infiltrating CD4⁺ and CD8⁺ T cells. In NB tumors with higher CD200 expression (CD200^high), we observed lower numbers of HLA-DR⁺CD14⁺ myeloid cells and less tumor-infiltrating CD4⁺ and CD8⁺ T cells. Moreover, we found that CD4⁺ and CD8⁺ T cells produced less IFN-γ and/or TNF-α in CD200^high NB tumors. Thus, CD200-CD200R pathway appears to downregulate anti-tumor immunity in the tumor microenvironment of NB tumors, and blockade of this pathway may be beneficial for NB patients.

Construction of Antibody Phage Libraries and Their Application in Veterinary Immunovirology

Antibody phage display (APD) technology has revolutionized the field of immunovirology with its application in viral disease diagnostics and antiviral therapy. This robust and versatile technology allows the expression of an antibody fused to a phage coat protein on the surface of a filamentous phage. The DNA sequence coding for the antibody is packaged within the phage, linking the phenotype to genotype. Antibody phage display inherits the ability to rapidly generate and modify or improve high-affinity monoclonal antibodies, rendering it indispensable in immunology. In the last two decades, phage-display-derived antibodies have been extensively used in human medicine as diagnostic and therapeutic modalities. Recently, they are also gaining significant ground in veterinary medicine. Even though these advancements are mainly biased towards economically important animals such as chicken, cattle, and pigs, they are laying the foundation of fulfilling the unmet needs of veterinary medicine as antibody-based biologics in viral diagnostics, therapeutics, and immunoprophylaxis. This review provides a brief overview of the construction of antibody phage libraries and their application in diagnosis, prevention, and control of infectious viral diseases in veterinary medicine in detail.

Leukemia-induced dysfunctional TIM-3+CD4+ bone marrow T cells increase risk of relapse in pediatric B-precursor ALL patients

Interaction of malignancies with tissue-specific immune cells has gained interest for prognosis and intervention of emerging immunotherapies. We analyzed bone marrow T cells (bmT) as tumor-infiltrating lymphocytes in pediatric precursor-B cell acute lymphoblastic leukemia (ALL). Based on data from 100 patients, we show that ALL is associated with late-stage CD4⁺ phenotype and loss of early CD8⁺ T cells. The inhibitory exhaustion marker TIM-3 on CD4⁺ bmT increased relapse risk (RFS = 94.6/70.3%) confirmed by multivariate analysis. The hazard ratio of TIM-3 expression nearly reached the hazard ratio of MRD (7.1 vs. 8.0) indicating that patients with a high frequency of TIM-3⁺CD4⁺ bone marrow T cells at initial diagnosis have a 7.1-fold increased risk to develop ALL relapse. Comparison of wild type primary T cells to CRISPR/Cas9-mediated TIM-3 knockout and TIM-3 overexpression confirmed the negative effect of TIM-3 on T cell responses against ALL. TIM-3⁺CD4⁺ bmT are increased in ALL overexpressing CD200, that leads to dysfunctional antileukemic T cell responses. In conclusion, TIM-3-mediated interaction between bmT and leukemia cells is shown as a strong risk factor for relapse in pediatric B-lineage ALL. CD200/TIM-3-signaling, rather than PD-1/PD-L1, is uncovered as a mechanism of T cell dysfunction in ALL with major implication for future immunotherapies.

The CD200-CD200R cross-talk helps Leishmania donovani to down regulate macrophage and CD4+CD44+ T cells effector functions in an NFκB independent manner

The lacuna in the knowledge of immunobiology, especially in visceral infections that are fatal if left untreated, are a major hurdle in getting a vaccine candidate for leishmaniasis. Till date, only a few drugs are available to combat human leishmaniasis and a vaccine candidate either prophylactic or preventive is still awaited. Therefore, identification of host and parasitic factors involved in the regulation of specific immune mechanisms are essentially needed. In this study, we observed that CD200-CD200R immune inhibitory axis regulates host macrophages effectors properties and helps antigen experienced T cells (CD4⁺CD44⁺ T cells) to acquire anti-inflammatory cytokines (IL-4, IL-10, TGF-β, IL-27) producing abilities in an NFkB independent manner. After CD200 blocking the macrophages effectively inhibited proliferation of Leishmania amastigotes and also induced the production of IL-12, IFN-γ, TNF-α and nitric oxide (NOx). Further, the blocking of CD200 signaling also restored macrophages MHC-II expression and helped CD4⁺CD44⁺ T cells to produce pro-inflammatory cytokines like IL-2, IL-12 and IFN-γ. The finding of this study suggested the importance of immune inhibitory mechanisms in controlling Leishmania growth and survival and therefore, requires more studies to understand its role in vaccine induced immunity.

NK Cell-Based Immune Checkpoint Inhibition

Immunotherapy, with an increasing number of therapeutic dimensions, is becoming an important mode of treatment for cancer patients. The inhibition of immune checkpoints, which are the source of immune escape for various cancers, is one such immunotherapeutic dimension. It has mainly been aimed at T cells in the past, but NK cells are a newly emerging target. Simultaneously, the number of checkpoints identified has been increasing in recent times. In addition to the classical NK cell receptors KIRs, LIRs, and NKG2A, several other immune checkpoints have also been shown to cause dysfunction of NK cells in various cancers and chronic infections. These checkpoints include the revolutionized CTLA-4, PD-1, and recently identified B7-H3, as well as LAG-3, TIGIT & CD96, TIM-3, and the most recently acknowledged checkpoint-members of the Siglecs family (Siglec-7/9), CD200 and CD47. An interesting dimension of immune checkpoints is their candidacy for dual-checkpoint inhibition, resulting in therapeutic synergism. Furthermore, the combination of immune checkpoint inhibition with other NK cell cytotoxicity restoration strategies could also strengthen its efficacy as an antitumor therapy. Here, we have undertaken a comprehensive review of the literature to date regarding NK cell-based immune checkpoints.

CD200-CD200R Pathway in the Regulation of Tumor Immune Microenvironment and Immunotherapy

Tumor-associated inflammation and immune responses are key components in the tumor microenvironment (TME) which regulate tumor growth, progression, and metastasis. Tumor-associated myeloid cells (TAMCs) are a group of cells that play multiple key roles including induction of tumor-associated inflammation/angiogenesis and regulation of tumor-specific T-cell responses. Thus, identification and characterization of key pathways that can regulate TAMCs are of critical importance for developing cancer immunotherapy. Recent studies suggest that CD200-CD200 receptor (CD200R) interaction may be important in regulating the TME via affecting TAMCs. In this chapter, we will give a brief overview of the CD200-CD200R axis, including the biology behind CD200-CD200R interaction and the role(s) it plays in tumor microenvironment and tumor growth, and activation/effector functions of T cells. We will also discuss CD200-CD200R's role as potential checkpoint molecules for cancer immunotherapy. Further investigation of the CD200-CD200R pathway will not only advance our understanding of tumor pathogenesis and immunity but also provide the rationale for CD200-CD200R-targeted immunotherapy of human cancer.

CD200-CD200R signaling and diseases: a potential therapeutic target?

CD200 and its receptor, CD200R, constitutes an endogenous inhibitory signaling, and is being increasingly recognized in studies of various central nervous system (CNS) disorders. Emerging data have demonstrated that neuronal CD200 binds to CD200R to modulate immune responses to pathogenic stimuli. However, on which component of the immune response that CD200-CD200R signaling acts is not well understood. In this review, we focused on cellular expression of the signaling, the effects on immune cell activation, and the function in pathological procedures of neurodegenerative diseases, in both clinical and experimental disease models. Essential functions of CD200-CD200R interaction and the treatment relevance have been elaborated. Immune responses to diseases under the control of CD200-CD200R axis were also discussed in the review.

Phase I study of samalizumab in chronic lymphocytic leukemia and multiple myeloma: blockade of the immune checkpoint CD200

PURPOSE

Samalizumab is a novel recombinant humanized monoclonal antibody that targets CD200, an immunoregulatory cell surface member of the immunoglobulin superfamily that dampens excessive immune responses and maintains self-tolerance. This first-in-human study investigated the therapeutic use of samalizumab as a CD200 immune checkpoint inhibitor in chronic lymphocytic leukemia (CLL) and multiple myeloma (MM).

EXPERIMENTAL DESIGN

Twenty-three patients with advanced CLL and 3 patients with MM were enrolled in an open-label phase 1 study (NCT00648739). Patients were assigned sequentially to one of 7 dose level cohorts (50 to 600 mg/m²) in a 3 + 3 study design, receiving a single dose of samalizumab intravenously once every 28 days. Primary endpoints were safety, identification of the maximum tolerated dose (MTD), and pharmacokinetics. Secondary endpoints were samalizumab binding to CD200, pharmacodynamic effects on circulating tumor cells and leukocyte subsets, and clinical responses.

RESULTS

Twenty-one patients received > 1 treatment cycle. Adverse events (AEs) were generally mild to moderate in severity. Samalizumab produced dose-dependent decreases in CD200 expression on CLL cells and decreased frequencies of circulating CD200 + CD4+ T cells that were sustained at higher doses. The MTD was not reached. Decreased tumor burden was observed in 14 CLL patients. One CLL patient achieved a durable partial response and 16 patients had stable disease. All MM patients had disease progression.

CONCLUSIONS

Samalizumab had a good safety profile and treatment was associated with reduced tumor burden in a majority of patients with advanced CLL. These preliminary positive results support further development of samalizumab as an immune checkpoint inhibitor.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00648739 registered April 1, 2008.

Interaction of CD200 Overexpression on Tumor Cells with CD200R1 Overexpression on Stromal Cells: An Escape from the Host Immune Response in Rectal Cancer Patients

CD200 imparts an immunoregulatory signal through its receptor, CD200R1, leading to the suppression of tumor specific immunity. The mechanism of CD200:CD200R1 signaling pathway is still uncertain. Our aim was to investigate the expression and localization of CD200 and its receptor CD200R1 and their clinical significance in rectal cancer patients. We examined the immunohistochemical expressions and localizations of CD200 and CD200R1 in 140 rectal cancer patients. Among the patients, 79 underwent the preoperative radiotherapy and the others were untreated prior to the surgery. In addition, 121 matched normal rectal mucosa samples were evaluated. The results of immunohistochemical analysis showed a strikingly high level of CD200 in tumor cells (p=0.001) and CD200R1 expression in normal mucosal epithelium and stromal cells. Importantly, CD200R1 was overexpressed in stromal cells of the metastatic cancer patients compared to patients without metastases (p=0.002). More than that, 87% of metastatic patients had a phenotype of upregulated CD200 in tumor cells accompanied by overexpressed CD200R1 in stromal cells. In addition, low levels of CD200 were correlated with improved overall survival in untreated patients. We showed that tumor-stroma communication through CD200 and its receptor interaction is selected in patients with high risk of relapse. High levels of these molecules support instigation of the far and local metastatic nest that provides solid ground for metastasis. Our current data also disclose a mechanism by which CD200:CD200R1 affects tumor progression and may strengthen the feasibility of targeting CD200 or CD200R1 as anticancer strategy.

Cellular distribution of CD200 receptor in rats and its interaction with cytomegalovirus e127 protein

CD200 is a membrane protein that interacts with CD200R on the surface of immune cells and delivers an inhibitory signal. In this study, we characterized the distribution of inhibitory CD200R in rats. In addition, we investigated if e127, a homologue of rat CD200 expressed by rat cytomegalovirus (RCMV), can suppress immune functions in vitro. RT-PCR analysis was carried out to test the expression of CD200R in different rat tissues and flow cytometry was performed to characterize CD200R at the cellular level. To test the inhibitory functions of e127, a co-culture system was utilized in which immune cells were incubated with e127-expressing cells. The strongest CD200R expression was detected in lymphoid organs such as bone marrow and spleen. Flow cytometry analyses showed that CD200R⁺ cells were mainly CD4^- dendritic cells (DC) and CD4⁺ T cells in the spleen. In blood, nearly all monocytes and granulocytes expressed CD200R and in bone marrow the NKRP1^low subset of natural killer cells highly expressed CD200R. In addition, both peritoneal macrophages and the NR8383 macrophage cell line carried CD200R. At the functional level, viral e127 conferred an inhibitory signal on TNFα and IL6 cytokine release from IFNγ-stimulated macrophages. However, e127 did not affect the cytotoxic activity of DC. CD200R in the rat is mainly expressed on myeloid cells but also on non-myeloid cell subsets, and RCMV e127 can deliver inhibitory signals to immune cells by engaging CD200R. The RCMV model provides a useful tool to study potential immune evasion mechanisms of the herpesviridae and opens new avenues for understanding and controlling herpesvirus infections.

An autologous tumor vaccine for CLL

Chronic Lymphocytic Leukemia B cells (CLL) are malignant cells which retain at least some functions of normal B cells. Paramount amongst the latter is that when such cells are appropriately stimulated, they are able to present antigens, including any potential tumor antigens, making them excellent choices as a candidate tumor vaccine. We show that following stimulation of CLL cells with Phorbol myristic acetate, IL-2, the TLR7 agonist imiquimod (P2I) and ionomycin (P2Iio), markedly increased expression of CD54 and CD83 was seen, indicative of B cell activation and a transition to antigen-presenting cells. However, this occurred in the context of augmented expression of the known immunoregulatory molecule, CD200. Accordingly we explored the effect of stimulation of CLL cells with P2Iio, followed by coating of cells with a non-depleting anti-CD200mAb, on the ability of those cells to immunize PBL in vitro to become cytotoxic to CLL cells, or to protect NOD-SCIDγc^null (NSG) mice from subsequent CLL tumor challenge. Our data indicate that this protocol is effective in inducing CD8⁺ CTL able to lyse CLL cells in vitro, and decrease tumor burden in vivo in spleen and marrow of mice injected with CLL cells. Pre-treatment of mice with a CD8 depleting antibody before vaccination with P2Iio/anti-CD200 coated cells abolished any protection seen. These data suggest a potential role for blockade of CD200 expression on CLL cells as a component of a tumor vaccination strategy.

Low expression of CD200 predicts shorter time-to-treatment in chronic lymphocytic leukemia

CD200, formerly known as OX-2, is a type I glycoprotein that is expressed on a variety of cell types. CD200 has been shown to be overexpressed in chronic lymphocytic leukemia (CLL). Although previous studies have confirmed the diagnostic value of CD200 in differentiating CLL from to other B-cell chronic lymphoproliferative disorders especially mantle cell lymphoma, whether CD200 has prognostic significance in CLL remains to be determined. We evaluated the mean fluorescence intensity (MFI) of CD200 in 307 consecutive, untreated patients with CLL in our center using flow cytometry. Using a CD200 MFI cutoff of 189.5, these cases could be divided into two groups. Patients with lower CD200 MFI (< 189.5) had a significantly shorter time-to-treatment (TTT) than those with higher CD200 MFI (≥ 189.5) (median TTT: 2 months vs 28 months, p = 0.0008). However, the effect of CD200 MFI on overall survival was not significant (CD200 MFI < 189.5: undefined vs CD200 MFI ≥ 189.5: undefined, P = 0.2379). In subgroup analysis, CD200 MFI retained its prognostic value in patients with favourable characteristics such as Binet stage A disease, mutated IGHV status, normal TP53 or negative CD38 expression. In conclusion, our study identified CD200 MFI as a potential prognostic factor in CLL.

Flow Cytometric Patterns of CD200 and CD1d Expression Distinguish CD10-Negative, CD5-Negative Mature B-Cell Lymphoproliferative Disorders

OBJECTIVES

The importance of distinguishing mature B-cell lymphoproliferative disorders (B-LPDs) is highlighted by the distinct treatments used for and varying prognoses seen in association with these different diseases. Immunophenotyping allows for accurate and efficient differentiation of many B-LPDs. Recently, we showed that CD200 is highly expressed in hairy cell leukemia (HCL) but not in marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma (LPL), or hairy cell leukemia-variant (HCL-v). Here, we assessed the usefulness of a flow cytometric panel combining CD200 and CD1d with CD25, CD103, and CD11c to distinguish CD10-, CD5- B-LPDs.

METHODS

We analyzed the expression of CD200 and CD1d by flow cytometric analysis in 79 cases of CD10-, CD5- mature B-LPDs.

RESULTS

Distinct patterns of CD200 and CD1d expression were seen in the examined B-LPDs. HCL showed bright positivity for CD200 along with positive staining for CD1d, whereas HCL-v showed low levels of expression for both markers. LPL demonstrated positive staining for CD200 in combination with dim to negative staining for CD1d. In contrast, MZL was commonly positive for CD1d and negative for CD200.

CONCLUSIONS

Flow cytometric analysis of CD200 and CD1d, along with CD25, CD103, and CD11c, can aid in the diagnosis of CD10-, CD5- mature B-LPDs.

Checkpoint Proteins in Pediatric Brain and Extracranial Solid Tumors: Opportunities for Immunotherapy

Pediatric brain and extracranial solid tumors are a diverse group of malignancies that represent almost half of all pediatric cancers. Standard therapy includes various combinations of surgery, cytotoxic chemotherapy, and radiation, which can be very harmful to a developing child, and survivors carry a substantial burden of long-term morbidities. Although these therapies have improved survival rates for children with solid tumors, outcomes still remain extremely poor for subsets of patients. Recently, immunosuppressive checkpoint molecules that negatively regulate immune cell function have been described. When found on malignant cells or in the tumor microenvironment, they contribute to immune evasion and tumor escape. Agents designed to inhibit these proteins have demonstrated significant efficacy in human adult solid tumor studies. However, there is limited research focusing on immune checkpoint molecules and inhibitors in pediatric solid tumors. In this review, we examine the current knowledge on immune checkpoint proteins with an emphasis on cytotoxic T lymphocyte antigen-4 (CTLA-4); programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1); OX-2 membrane glycoprotein (CD200); and indoleamine 2,3-dioxygenase (IDO). We review T-cell signaling, the mechanisms of action of these checkpoint molecules, pediatric preclinical studies on checkpoint proteins and checkpoint blockade, pediatric checkpoint inhibitor clinical trials conducted to date, and future immunotherapy opportunities for childhood cancers. Clin Cancer Res; 23(2); 342-50. ©2016 AACR.

CD200 Expression on Plasma Cell Myeloma Cells is Associated with the Efficacies of Bortezomib, Lenalidomide and Thalidomide

Plasma cell myeloma (PCM) is a devastating disease with a highly heterogeneous outcome, with survival ranging from a few months to longer than 10 years. Treatment of multiple myeloma has changed markedly in the past decade due to the development of new drugs such as bortezomib, lenalidomide and thalidomide, which have greatly improved the outcome of PCM. The clinical and prognostic value of immunophenotyping in PCM remains questionable. The aim of this study was to determine the diagnostic and prognostic significance of CD200 expression in newly diagnosed PCM. We retrospectively reviewed the records of 107 patients newly diagnosed with PCM at Showa University Hospital between January 2004 and September 2013. Expression of CD200 was studied by immunohistochemistry. Clinical and pathological parameters were compared between CD200-positive and CD200-negative cases. CD200-positive PCM cases had lower serum albumin (p = 0.0001) compared to those without CD200 expression. Our results showed no significant difference in median overall survival between patients with CD200-positive and CD200-negative PCM. However, there was a strong correlation between CD200 expression and serum albumin level. In the CD200-negative group, median overall survival was significantly longer in patients who received new drug treatment. These findings suggest that CD200 expression is a useful marker for evaluation of the severity of PCM and that lack of CD200 expression may improve the sensitivity of PCM to therapy with new drugs.

Radiation-Guided Peptide Delivery in a Mouse Model of Nasopharyngeal Carcinoma

Purpose. This study aimed to evaluate the characteristics of the HVGGSSV peptide, exploring radiation-guided delivery in a mouse model of nasopharyngeal carcinoma. Methods. Mice with CNE-1 nasopharyngeal carcinoma were assigned to two different groups treated with Cy7-NHS and Cy7-HVGGSSV, respectively. Meanwhile, each mouse received a single dose of 3 Gy radiation. Biological distribution of the recombinant peptide was assessed on an in vivo small animal imaging system. Results. The experimental group showed maximum fluorescence intensity in irradiated tumors treated with Cy7-labeled HVGGSSV, while untreated (0 Gy) control tumors showed lower intensity levels. Fluorescence intensities of tumors in the right hind limbs of experimental animals were 7.84 × 10⁷ ± 1.13 × 10⁷, 1.35 × 10⁸ ± 2.66 × 10⁷, 4.05 × 10⁸ ± 1.75 × 10⁷, 5.57 × 10⁸ ± 3.47 × 10⁷, and 9.26 × 10⁷ ± 1.73 × 10⁷ photons/s/cm² higher compared with left hind limb values at 1, 2, 15, 24, and 48 h, respectively. Fluorescence intensities of tumor in the right hind limbs of the experimental group were 1.66 × 10⁸ ± 1.71 × 10⁷, 1.51 × 10⁸ ± 3.23 × 10⁷, 5.38 × 10⁸ ± 1.96 × 10⁷, 5.89 × 10⁸ ± 3.57 × 10⁷, and 1.62 × 10⁸ ± 1.69 × 10⁷ photons/s/cm² higher compared with control group values at 1, 2, 15, 24, and 48 h, respectively. Fluorescence was not specifically distributed in the control group. Compared with low fluorescence intensity in the heart, lungs, and tumors, high fluorescence distribution was found in the liver and kidney at 48 h. Conclusions. HVGGSSV was selectively bound to irradiated nasopharyngeal carcinoma, acting as a targeting transport carrier for radiation-guided drugs that are mainly metabolized in the kidney and liver.

A Critical Role for CD200R Signaling in Limiting the Growth and Metastasis of CD200+ Melanoma

CD200 is a cell surface glycoprotein that functions through engaging CD200R on cells of the myeloid lineage and inhibits their functions. Expression of CD200 was implicated in a variety of human cancer cells, including melanoma cells; however, its roles in tumor growth and immunity are not clearly understood. In this study, we used CD200R-deficient mice and the B16 tumor model to evaluate this issue. We found that CD200R-deficient mice exhibited accelerated growth of CD200(+), but not CD200(-), B16 tumors. Strikingly, CD200R-deficient mice receiving CD200(+) B16 cells i.v. exhibited massive tumor growth in multiple organs, including liver, lung, kidney, and peritoneal cavity, whereas the growth of the same tumors in wild-type mice was limited. CD200(+) tumors grown in CD200R-deficient mice contained higher numbers of CD11b(+)Ly6C(+) myeloid cells, exhibited increased expression of VEGF and HIF1α genes with increased angiogenesis, and showed significantly reduced infiltration of CD4(+) and CD8(+) T cells, presumably as the result of reduced expression of T cell chemokines, such as CXCL9 and CXCL16. The liver from CD200R-deficient mice, under metastatic growth of CD200(+) tumors, contained significantly increased numbers of CD11b(+)Gr1(-) myeloid cells and Foxp3(+) regulatory T cells and reduced numbers of NK cells. Liver T cells also had a reduced capacity to produce IFN-γ or TNF-α. Taken together, we revealed a critical role for CD200R signaling in limiting the growth and metastasis of CD200(+) tumors. Thus, targeting CD200R signaling may potentially interfere with the metastatic growth of CD200(+) tumors, like melanoma.

Chronic lymphocytic leukemia cells diversify and differentiate in vivo via a nonclassical Th1-dependent, Bcl-6-deficient process

Xenografting primary tumor cells allows modeling of the heterogeneous natures of malignant diseases and the influences of the tissue microenvironment. Here, we demonstrate that xenografting primary chronic lymphocytic leukemia (CLL) B lymphocytes with activated autologous T cells into alymphoid mice results in considerable CLL B cell division and sizable T cell expansion. Nevertheless, most/all CD5⁺CD19⁺ cells are eventually lost, due in part to differentiation into antibody-secreting plasmablasts/plasma cells. CLL B cell differentiation is associated with isotype class switching and development of new IGHV-D-J mutations and occurs via an activation-induced deaminase-dependent pathway that upregulates IRF4 and Blimp-1 without appreciable levels of the expected Bcl-6. These processes were induced in IGHV-unmutated and IGHV-mutated clones by Th1-polarized T-bet⁺ T cells, not classical T follicular helper (Tfh) cells. Thus, the block in B cell maturation, defects in T cell action, and absence of antigen-receptor diversification, which are often cardinal characteristics of CLL, are not inherent but imposed by external signals and the microenvironment. Although these activities are not dominant features in human CLL, each occurs in tissue proliferation centers where the mechanisms responsible for clonal evolution operate. Thus, in this setting, CLL B cell diversification and differentiation develop by a nonclassical germinal center-like reaction that might reflect the cell of origin of this leukemia.

Regulatory B lymphocyte functions should be considered in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by an abnormal expansion of mature B cells in the bone marrow and their accumulation in blood and secondary lymphoid organs. Tumor CLL cells share expression of various surface molecules with many subsets of B cells and have several common characteristics with regulatory B cells (B regs). However, the identification of B regs and their role in CLL remain elusive. The aim of this review is to summarize recent works regarding the regulatory and phenotypic characteristic of B regs and their associated effects on the immune system. It is also meant to highlight their potential importance with regards to the immunotherapeutic response.

Negative immune checkpoints on T lymphocytes and their relevance to cancer immunotherapy

The term 'inhibitory checkpoint' refers to the broad spectrum of co-receptors expressed by T cells that negatively regulate T cell activation thus playing a crucial role in maintaining peripheral self-tolerance. Co-inhibitory receptor ligands are highly expressed by a variety of malignancies allowing evasion of anti-tumour immunity. Recent studies demonstrate that manipulation of these co-inhibitory pathways can remove the immunological brakes that impede endogenous immune responses against tumours. Antibodies that block the interactions between co-inhibitory receptors and their ligands have delivered very promising clinical responses, as has been shown by recent successful trials targeting the CTLA-4 and PD-1 pathways. In this review, we discuss the mechanisms of action and expression pattern of co-inhibitory receptors on different T cells subsets, emphasising differences between CD4(+) and CD8(+) T cells. We also summarise recent clinical findings utilising immune checkpoint blockade.

Brain innate immunity in the regulation of neuroinflammation: therapeutic strategies by modulating CD200-CD200R interaction involve the cannabinoid system

The central nervous system (CNS) innate immune response includes an arsenal of molecules and receptors expressed by professional phagocytes, glial cells and neurons that is involved in host defence and clearance of toxic and dangerous cell debris. However, any uncontrolled innate immune responses within the CNS are widely recognized as playing a major role in the development of autoimmune disorders and neurodegeneration, with multiple sclerosis (MS) Alzheimer's disease (AD) being primary examples. Hence, it is important to identify the key regulatory mechanisms involved in the control of CNS innate immunity and which could be harnessed to explore novel therapeutic avenues. Neuroimmune regulatory proteins (NIReg) such as CD95L, CD200, CD47, sialic acid, complement regulatory proteins (CD55, CD46, fH, C3a), HMGB1, may control the adverse immune responses in health and diseases. In the absence of these regulators, when neurons die by apoptosis, become infected or damaged, microglia and infiltrating immune cells are free to cause injury as well as an adverse inflammatory response in acute and chronic settings. We will herein provide new emphasis on the role of the pair CD200-CD200R in MS and its experimental models: experimental autoimmune encephalomyelitis (EAE) and Theiler’s virus induced demyelinating disease (TMEV-IDD). The interest of the cannabinoid system as inhibitor of inflammation prompt us to introduce our findings about the role of endocannabinoids (eCBs) in promoting CD200-CD200 receptor (CD200R) interaction and the benefits caused in TMEV-IDD. Finally, we also review the current data on CD200-CD200R interaction in AD, as well as, in the aging brain.

Differential expression of CD200 in B-cell neoplasms by flow cytometry can assist in diagnosis, subclassification, and bone marrow staging

OBJECTIVES

To analyze CD200 expression by flow cytometry in a large series of B-cell neoplasms in a variety of tissue types in comparison with benign B-lineage cells.

METHODS

We measured CD200 expression levels in 505 peripheral blood (PB), bone marrow (BM), and lymphoid tissue biopsy specimens, including 364 cases positive for B-cell leukemias and lymphomas.

RESULTS

CD200 expression in chronic lymphocytic leukemia cases was as bright as or brighter than normal PB B cells in nearly all cases, while mantle cell lymphoma (MCL) cases were usually dim or negative. However, rare MCL cases (about 5%) were moderately bright for CD200. Marginal zone lymphomas varied by subtype, with nodal cases brighter, splenic cases dimmer, and extranodal cases heterogeneous for CD200 expression. Follicular lymphoma (FL) cells were brighter for CD200 in BM specimens than in lymph nodes. In some BM specimens, dim CD200 could distinguish FL cells from background hematogones. Large B-cell lymphomas of the non-germinal center type tended to be brighter for CD200 than those of the germinal center type, while Burkitt lymphomas were negative.

CONCLUSIONS

CD200 staining by flow cytometry can be useful in the differential diagnosis of B-cell neoplasms and in their detection in the BM.

Spiradenoma and cylindroma originate from the hair follicle bulge and not from the eccrine sweat gland: an immunohistochemical study with CD200 and other stem cell markers

BACKGROUND

Spiradenoma and cylindroma have historically been described as sweat gland tumors and have often been considered to be of eccrine lineage. However, (a) associations with trichoepitheliomas in Brooke-Spiegler syndrome or with trichoepitheliomas and milia in Rasmussen syndrome, (b) neoplastic combinations with hair follicle tumors in solitary cases, and (c) anatomical considerations support a folliculosebaceous-apocrine lineage. Follicular stem cell markers may allow for further characterization of these neoplasms.

METHODS

A total of 97 tumors were examined for the expression pattern of follicular stem cell markers cytokeratin 15 (CK15), cytokeratin 19 (CK19), pleckstrin homology-like domain, family A, member 1 (PHLDA1), and CD200. The tumors were comprised of 27 spiradenomas, 30 cylindromas, 16 hidradenomas, 19 poromas, 4 dermal duct tumors and 1 hidroacanthoma simplex.

RESULTS

All spiradenomas and cylindromas were CD200-positive whereas the other tumors classified as eccrine in lineage were all CD200-negative. CK15 also discriminated between spiradenomas and cylindromas and the remaining neoplasms but not to the degree of CD200. PHLDA1 and CK19 were noncontributory.

CONCLUSIONS

It is concluded that both spiradenoma and cylindroma are not eccrine but follicular tumors. More specifically, it is proposed that both adnexal neoplasms are derived from the hair follicle bulge and as such represent one of the least differentiated follicular tumors.

Comparison of immunity in mice cured of primary/metastatic growth of EMT6 or 4THM breast cancer by chemotherapy or immunotherapy

PURPOSE

We have compared cure from local/metastatic tumor growth in BALB/c mice receiving EMT6 or the poorly immunogenic, highly metastatic 4THM, breast cancer cells following manipulation of immunosuppressive CD200:CD200R interactions or conventional chemotherapy.

METHODS

We reported previously that EMT6 tumors are cured in CD200R1KO mice following surgical resection and immunization with irradiated EMT6 cells and CpG oligodeoxynucleotide (CpG), while wild-type (WT) animals developed pulmonary and liver metastases within 30 days of surgery. We report growth and metastasis of both EMT6 and a highly metastatic 4THM tumor in WT mice receiving iv infusions of Fab anti-CD200R1 along with CpG/tumor cell immunization. Metastasis was followed both macroscopically (lung/liver nodules) and microscopically by cloning tumor cells at limiting dilution in vitro from draining lymph nodes (DLN) harvested at surgery. We compared these results with local/metastatic tumor growth in mice receiving 4 courses of combination treatment with anti-VEGF and paclitaxel.

RESULTS

In WT mice receiving Fab anti-CD200R, no tumor cells are detectable following immunotherapy, and CD4+ cells produced increased TNFα/IL-2/IFNγ on stimulation with EMT6 in vitro. No long-term cure was seen following surgery/immunotherapy of 4THM, with both microscopic (tumors in DLN at limiting dilution) and macroscopic metastases present within 14 d of surgery. Chemotherapy attenuated growth/metastases in 4THM tumor-bearers and produced a decline in lung/liver metastases, with no detectable DLN metastases in EMT6 tumor-bearing mice-these latter mice nevertheless showed no significantly increased cytokine production after restimulation with EMT6 in vitro. EMT6 mice receiving immunotherapy were resistant to subsequent re-challenge with EMT6 tumor cells, but not those receiving curative chemotherapy. Anti-CD4 treatment caused tumor recurrence after immunotherapy, but produced no apparent effect in either EMT6 or 4THM tumor bearers after chemotherapy treatment.

CONCLUSION

Immunotherapy, but not chemotherapy, enhances CD4+ immunity and affords long-term control of breast cancer growth and resistance to new tumor foci.

Addressing the Inflammatory Response to Clinically Relevant Polymers by Manipulating the Host Response Using ITIM Domain-Containing Receptors

Tissue contacting surfaces of medical devices initiate a host inflammatory response, characterized by adsorption of blood proteins and inflammatory cells triggering the release of cytokines, reactive oxygen species (ROS) and reactive nitrogen species (RNS), in an attempt to clear or isolate the foreign object from the body. This normal host response contributes to device-associated pathophysiology and addressing device biocompatibility remains an unmet need. Although widespread attempts have been made to render the device surfaces unreactive, the establishment of a completely bioinert coating has been untenable and demonstrates the need to develop strategies based upon the molecular mechanisms that define the interaction between host cells and synthetic surfaces. In this review, we discuss a family of transmembrane receptors, known as immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing receptors, which show promise as potential targets to address aberrant biocompatibility. These receptors repress the immune response and ensure that the intensity of an immune response is appropriate for the stimuli. Particular emphasis will be placed on the known ITIM-containing receptor, Signal Regulatory Protein Alpha (SIRPhα), and its cognate ligand CD47. In addition, this review will discuss the potential of other ITIM-containing proteins as targets for addressing the aberrant biocompatibility of polymeric biomaterials.

The rhesus rhadinovirus CD200 homologue affects immune responses and viral loads during in vivo infection

Rhesus macaque rhadinovirus (RRV) is a gammaherpesvirus of rhesus macaque (RM) monkeys that is closely related to human herpesvirus 8 (HHV-8)/Kaposi's Sarcoma-associated herpesvirus (KSHV), and it is capable of inducing diseases in simian immunodeficiency virus (SIV)-infected RM that are similar to those seen in humans coinfected with HIV and HHV-8. Both HHV-8 and RRV encode viral CD200 (vCD200) molecules that are homologues of cellular CD200, a membrane glycoprotein that regulates immune responses and helps maintain immune homeostasis via interactions with the CD200 receptor (CD200R). Though the functions of RRV and HHV-8 vCD200 molecules have been examined in vitro, the precise roles that these viral proteins play during in vivo infection remain unknown. Thus, to address the contributions of RRV vCD200 to immune regulation and disease in vivo, we generated a form of RRV that lacked expression of vCD200 for use in infection studies in RM. Our data indicated that RRV vCD200 expression limits immune responses against RRV at early times postinfection and also impacts viral loads, but it does not appear to have significant effects on disease development. Further, examination of the distribution pattern of CD200R in RM indicated that this receptor is expressed on a majority of cells in peripheral blood mononuclear cells, including B and T cells, suggesting potentially wider regulatory capabilities for both vCD200 and CD200 that are not strictly limited to myeloid lineage cells. In addition, we also demonstrate that RRV infection affects CD200R expression levels in vivo, although vCD200 expression does not play a role in this phenomenon.

IMPORTANCE

Cellular CD200 and its receptor, CD200R, compose a pathway that is important in regulating immune responses and is known to play a role in a variety of human diseases. A number of pathogens have been found to modulate the CD200-CD200R pathway during infection, including human herpesvirus 8 (HHV-8), the causative agent of Kaposi's sarcoma and B cell neoplasms in AIDS patients, and a closely related primate virus, rhesus macaque rhadinovirus (RRV), which infects and induces disease in rhesus macaque monkeys. HHV-8 and RRV encode homologues of CD200, termed vCD200, which are thought to play a role in preventing immune responses against these viruses. However, neither molecule has been studied in an in vivo model of infection to address their actual contributions to immunoregulation and disease. Here we report findings from our studies in which we analyzed the properties of a mutant form of RRV that lacks vCD200 expression in infected rhesus macaques.

Targeted therapy aimed at cancer stem cells: Wilms' tumor as an example

Wilms' tumor (WT), a common renal pediatric solid tumor, serves as a model for a malignancy formed by renal precursor cells that have failed to differentiate properly. Here we review recent evidence showing that the tumors' heterogeneous cell population contains a small fraction of cancer stem cells (CSC) identified by two markers: Neural Cell Adhesion Molecule 1 (NCAM1) expression and Aldehyde dehydrogenase 1 (ALDH1) enzymatic activity. In vivo studies show these CSCs to both self-renew and differentiate to give rise to all tumor components. Similar to other malignancies, the identification of a specific CSC fraction has allowed the examination of a novel targeted therapy, aimed at eradicating the CSC population. The loss of CSCs abolishes the tumor's ability to sustain and propagate, hence, causing tumor degradation with minimal damage to normal tissue.