CD57+ T-cells are a subpopulation of T-follicular helper cells in nodular lymphocyte predominant Hodgkin lymphoma

Flow Cytometric Detection of the Double-Positive (CD4+CD8+)/PD-1bright T-Cell Subset Is Useful in Diagnosing Nodular Lymphocyte-Predominant Hodgkin Lymphoma

CONTEXT.—

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is characterized by neoplastic lymphocyte-predominant cells frequently rimmed by CD3+/CD57+/programmed death receptor-1 (PD-1)+ T cells. Because of the rarity of lymphocyte-predominant cells in most cases, flow cytometric studies on NLPHL often fail to show evidence of malignancy.

OBJECTIVE.—

To evaluate the diagnostic utility of PD-1 in detecting NLPHL by flow cytometry, in conjunction with the CD4:CD8 ratio and the percentage of T cells doubly positive for CD4 and CD8.

DESIGN.—

Flow cytometric data obtained from cases of NLPHL (n = 10), classical Hodgkin lymphoma (n = 20), B-cell non-Hodgkin lymphoma (n = 22), T-cell non-Hodgkin lymphoma (n = 5), benign lymphoid lesions (n = 20), angioimmunoblastic T-cell lymphomas (n = 6) and T-cell/histiocyte-rich large B-cell lymphomas (n = 2) were analyzed and compared.

RESULTS.—

Compared with the other groups, NLPHL showed significantly higher values in the following parameters: CD4:CD8 ratio, percentage of T cells doubly positive for CD4 and CD8, percentage of PD-1-positive T cells, and median fluorescence intensity of PD-1 expression in the doubly positive for CD4 and CD8 subset. Using a scoring system (0-4) based on arbitrary cutoffs for these 4 parameters, all 10 NLPHL cases scored 3 or higher, as compared with only 3 cases from the other groups, producing an overall sensitivity of 100% and a specificity of 96% (72 of 75). Two of the 3 outliers were non-Hodgkin lymphoma, and both showed definitive immunophenotypic abnormalities leading to the correct diagnosis. The remaining outlier was a case of T-cell/histiocyte-rich large B-cell lymphoma.

CONCLUSIONS.—

The inclusion of anti-PD-1 in flow cytometry is useful for detecting NLPHL in fresh tissue samples, most of which would have otherwise been labeled as nondiagnostic or reactive lymphoid processes.

An approach to small lymph node biopsies: pearls and pitfalls of reporting in the real world

Recent advances in interventional radiology have resulted in the utilization of small lymph node biopsies, including fine-needle aspiration (FNA) and core needle biopsy (CNB) as an initial diagnostic tool in hematopathology. A major challenge to the utilization of FNA and CNB is the limited-to-scant tissue often available. We propose delegation of the task of handling biopsy specimens to the laboratory staff by the biopsy operators, in order to optimize the utilization of the specimen. Furthermore, in order to effectively diagnose hematolymphoid neoplasms a variety of ancillary tests including immunohistochemistry, flow cytometry, molecular analysis, florescence in situ hybridization (FISH) are necessary. We propose morphological evaluation coupled with careful utilization of ancillary studies along with clinical correlation to approach the correct diagnosis. Our morphological assessment considers the types of proliferating cell population: mainly small cells, sheets of large cells, or scattered large cells among small cells. This is followed by employment of the corresponding immunopanel to assess the differential diagnosis in each of the three categories. We also elaborate on the importance for pathologists to become proficient in understanding the limitations of small tissue biopsies as well as the differences in interpretation, and wording their reports to help clinicians and direct them to further investigate and/or to re-biopsy when necessary.

Lymphocyte predominant cells of nodular lymphocyte predominant Hodgkin lymphoma interact with rosetting T cells in an immunological synapse

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a subtype of Hodgkin lymphoma with a preserved B-cell phenotype and follicular T helper (T_FH ) cells rosetting around the tumor cells, the lymphocyte-predominant (LP) cells. As we recently described reactivity of the B-cell receptors of LP cells of some NLPHL cases with Moraxella spp. proteins, we hypothesized that LP cells could present peptides to rosetting T cells in a major histocompatibility complex class II (MHCII)-bound manner. Rosetting PD1⁺ T cells were present in the majority of NLPHL cases, both in typical (17/20) and variant patterns (16/19). In most cases, T-cell rosettes were CD69⁺ (typical NLPHL, 17/20; NLPHL variant, 14/19). Furthermore, both MHCII alpha and beta chains were expressed in the LP cells in 23/39 NLPHL. Proximity ligation assay and confocal laser imaging demonstrated interaction of the MHCII beta chain expressed by the LP cells and the T-cell receptor alpha chain expressed by rosetting T cells. We thus conclude that rosetting T cells in NLPHL express markers that are encountered after antigenic exposure, that MHCII is expressed by the LP cells, and that LP cells interact with rosetting T cells in an immunological synapse in a subset of cases. As they likely receive growth stimulatory signals in this way, blockade of this interaction, for example, by PD1-directed checkpoint inhibitors, could be a treatment option in a subset of cases in the future.

Lymphocyte predominant Hodgkin lymphoma, antigen-driven after all?

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) was suggested as an entity separate from other types of Hodgkin lymphoma 40 years ago and recognized in the WHO classification in 2001. Based on its relatively benign course with late distant relapses, relation with lymph node hyperplasia with progressively transformed germinal centers, presence of clonal immunoglobulin gene rearrangements with somatic hypermutations and ongoing mutations, and relation with a number of inherited defects affecting the immune system, it has been suspected that NLPHL might be antigen-driven. Recent evidence has shown that cases of IgD-positive NLPHL are associated with infection by Moraxella catarrhalis, a common bacterium in the upper respiratory tract and in lymph nodes. This review summarizes the evidence for NLPHL as a B-cell lymphoma involving follicular T-lymphocytes normally found in germinal centers, its molecular features and relation to inherited immune defects, and its relation and differential diagnosis from similar entities. Finally, it discusses the evidence that in many cases a watch and wait policy might be a viable initial management strategy. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Tissue memory CD4+ T cells expressing IL-7 receptor-alpha (CD127) preferentially support latent HIV-1 infection

The primary reservoir for HIV is within memory CD4+ T cells residing within tissues, yet the features that make some of these cells more susceptible than others to infection by HIV is not well understood. Recent studies demonstrated that CCR5-tropic HIV-1 efficiently enters tissue-derived memory CD4+ T cells expressing CD127, the alpha chain of the IL7 receptor, but rarely completes the replication cycle. We now demonstrate that the inability of HIV to replicate in these CD127-expressing cells is not due to post-entry restriction by SAMHD1. Rather, relative to other memory T cell subsets, these cells are highly prone to undergoing latent infection with HIV, as revealed by the high levels of integrated HIV DNA in these cells. Host gene expression profiling revealed that CD127-expressing memory CD4+ T cells are phenotypically distinct from other tissue memory CD4+ T cells, and are defined by a quiescent state with diminished NFκB, NFAT, and Ox40 signaling. However, latently-infected CD127+ cells harbored unspliced HIV transcripts and stimulation of these cells with anti-CD3/CD28 reversed latency. These findings identify a novel subset of memory CD4+ T cells found in tissue and not in blood that are preferentially targeted for latent infection by HIV, and may serve as an important reservoir to target for HIV eradication efforts.

Expression of the immune checkpoint receptor TIGIT in Hodgkin's lymphoma

Hodgkin's lymphoma (HL) is characterized by a high background of inflammatory cells which play an important role for the pathogenesis of the disease. T cell immunoreceptor with Ig and ITIM domains (TIGIT) is an inhibitory immune checkpoint receptor and a putative target for novel immunotherapies. To study patterns of TIGIT expression in the T cell background surrounding malignant cells including Hodgkin cells, Reed-Sternberg cells and histiocytic cells, a microenvironment (ME) tissue microarray (TMA) was constructed from tissue punches measuring 2 mm in diameter obtained from formalin-fixed tissue samples of Hodgkin's lymphoma lymph nodes (n = 40) and normal human tonsil (n = 2). The ME-TMA was stained by brightfield and fluorescence multiplex immunohistochemistry (IHC) to evaluate expression levels of TIGIT and PD-1 as well as standard lymphocyte markers (CD3, CD8, CD4, FOXP3) in the lymphocytic background. All analyzed cases of HL contained 9-99% (median: 86%) of TIGIT+ lymphoid cells. In general, TIGIT localized to the same cells as PD-1. Strikingly, expression levels of TIGIT and PD-1 were highly variable among the analyzed samples. Highest levels of TIGIT and PD-1 were found in one sample of nodular lymphocytic-predominant HL (NLPHL). In conclusion, TIGIT expression is highly variable between patients with Hodgkin's lymphoma. Our results encourage further studies evaluating the role of TIGIT as a target for immunotherapies in Hodgkin's lymphoma.

Visualizing the Immune System: Providing Key Insights into HIV/SIV Infections

Immunological inductive tissues, such as secondary lymphoid organs, are composed of distinct anatomical microenvironments for the generation of immune responses to pathogens and immunogens. These microenvironments are characterized by the compartmentalization of highly specialized immune and stromal cell populations, as well as the presence of a complex network of soluble factors and chemokines that direct the intra-tissue trafficking of naïve and effector cell populations. Imaging platforms have provided critical contextual information regarding the molecular and cellular interactions that orchestrate the spatial microanatomy of relevant cells and the development of immune responses against pathogens. Particularly in HIV/SIV disease, imaging technologies are of great importance in the investigation of the local interplay between the virus and host cells, with respect to understanding viral dynamics and persistence, immune responses (i.e., adaptive and innate inflammatory responses), tissue structure and pathologies, and changes to the surrounding milieu and function of immune cells. Merging imaging platforms with other cutting-edge technologies could lead to novel findings regarding the phenotype, function, and molecular signatures of particular immune cell targets, further promoting the development of new antiviral treatments and vaccination strategies.

Characterization of the Microenvironment of Nodular Lymphocyte Predominant Hodgkin Lymphoma

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is characterized by a low percentage of neoplastic lymphocyte predominant (LP) cells in a background of lymphocytes. The goal of this study is to characterize the microenvironment in NLPHL. Ten NLPHL cases and seven reactive lymph nodes (RLN) were analyzed by flow cytometry for the main immune cells and multiple specific subpopulations. To discriminate between cells in or outside the tumor cell area, we used CD26. We observed significantly lower levels of CD20+ B-cells and CD56+ NK cells and higher levels of CD4+ T-cells in NLPHL in comparison to RLN. In the subpopulations, we observed increased numbers of PD-1+CD4+ T follicular helper cells (TFH), CD69+CD4+ and CD69+CD8+ T-cells and CCR7-CD45RA-CD4+ effector memory T-cells, while FoxP3+CD4+ T regulatory cells (Tregs) and CCR7-CD45RA+ terminally differentiated CD4+ T-cells were decreased in NLPHL compared to RLN. CD69+ cells were increased in the tumor cell area in CD4+ and CD8+ T-cells, while FoxP3+CD25+CD4+ Tregs and CD25+CD8+ T-cells were significantly increased outside the tumor area. Thus, we show a markedly altered microenvironment in NLPHL, with lower numbers of NK cells and Tregs. PD-1+CD4+ and CD69+ T-cells were located inside, and Tregs and CD25+CD8+ cells outside the tumor cell area.