{"doi":"10.1002/hon.70093_83","title":"83 | SINGLE CELL ANALYSIS REVEALS EXTENSIVE IMMUNE EXHAUSTION AND MEMORY‐CELL LIKE ORIGIN IN FOLLICULAR LYMPHOMA (FL) WITH INCREASED IRF4 EXPRESSION","abstract":"E. Contreras Guzman and S. Dasari equally contributing authors. 20% of FL patients relapse early with poor outcomes. We showed that this unfavorable group displays increased expression of IRF4, dysregulated immune signaling and an immunosuppressive microenvironment. However, high-resolution studies are required to define biological determinants of FL with different IRF4 status. To address this, we performed scRNA-seq/scBCR-seq of 21 newly diagnosed FL (n = 10 IRF4hi and 11 IRF4lo). UMAP clustering distinguished B cells from immune cells. The immune cells were reclustered in 26 subsets based on gene expression profiles and annotated using key marker genes as T cells, NK, macrophages, mast cells, myeloid and plasmacytoid dendritic cells (Figure 1A). We found a higher abundance of macrophages, Treg, TFH exh, T proliferating and T effector memory (Tem) clusters with cytotoxic and exhaustion markers in IRF4hi FL compared to those IRF4lo. Conversely, T central memory (Tcm) and CD8 naïve clusters were prevalent in IRF4lo tumors. Differential gene expression in T cell clusters from IRF4hi versus IRF4lo FL revealed a marked upregulation of multiple immune exhaustion genes including TOX2, TIGIT and LAG3 (Figure 1B). GSEA showed enrichment in signatures involved in T cell immunity and TNFα signaling. CellChat analysis found a stronger interaction between malignant B cells and multiple T exh cell subsets and Treg cells in IRF4hi versus IRF4lo FL. Notably, the CD70-CD27 signaling axis was present in IRF4hi FL but not in IRF4lo FL. This was accompanied by an increased signaling through BTLA, IL2 and CD80 (Figure 1C). We further showed that the malignant B cells with increased IRF4 expression were those responsible for the altered crosstalk with T cells. Focusing on malignant B cells, we calculated the proportion of Ig isotypes across tumor samples and found a higher proportion of IgM+ cells in IRF4hi FL (59% vs. 37%), while IRF4lo tumors had a greater number of IgG+ cells (60% vs. 38%). Further analysis within each sample revealed that a larger number of IRF4hi malignant B cells expressed IgM+ compared to those that were IRF4lo, thus representing less mature, non-class switched cells. Next, we reclustered the malignant B cells into nine subsets and annotated them based on key marker genes (Figure 1D). We observed a significant expansion of plasmablast, dark zone (DZ) and transitioning cells in IRF4hi FL, while light zone, recycling and pre-memory B cells (pre-MB) were more abundant in IRF4lo FL (Figure 1E). GSEA showed enrichment for BCR, NFkB signaling, antigen presentation and immune response signatures in B cell clusters from IRF4hi versus IRF4lo FL. Using the Slingshot algorithm, we found that IRF4hi FL originate from MB and have 6 times higher risk to transform to an aggressive lymphoma, while IRF4lo FL arise from DZ cells (Figure 1F). Overall, our studies showed extensive T cell exhaustion in IRF4hi FL and link the altered crosstalk to malignant B cells with increased IRF4 expression. We also uncovered the emergence of IRF4hi FL from memory-like precursors. Research funding declaration: The Authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the abstract apart from those disclose. Encore Abstract: EHA 2025 Keywords: microenvironment; tumor biology and heterogeneity; indolent non-Hodgkin lymphoma No potential sources of conflict of interest.","journal":"Hematological Oncology","year":2025,"id":568539,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9489,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":235319,"name":"Surendra Dasari","orcid":"0000-0002-7972-3556","position":1,"is_corresponding":false},{"id":785975,"name":"Vaishali Bhardwaj","orcid":"0000-0002-2880-0187","position":2,"is_corresponding":false},{"id":461051,"name":"Pinku Mukherjee","orcid":"0000-0002-6782-3576","position":3,"is_corresponding":false},{"id":273486,"name":"Xinyi Tang","orcid":"0000-0002-1889-4562","position":4,"is_corresponding":false},{"id":574625,"name":"Zhi-Zhang Yang","orcid":"0000-0002-1468-2300","position":5,"is_corresponding":false},{"id":247014,"name":"Laura Pasqualucci","orcid":"0000-0001-6819-7370","position":6,"is_corresponding":false},{"id":237080,"name":"Mark J. Shlomchik","orcid":"0000-0002-2152-0959","position":7,"is_corresponding":false},{"id":24597,"name":"Harinder Singh","orcid":"0000-0002-6330-8526","position":8,"is_corresponding":false},{"id":262228,"name":"Stephen M. Ansell","orcid":"0000-0003-1244-6758","position":9,"is_corresponding":false},{"id":255852,"name":"Patrizia Mondello","orcid":"0000-0002-0355-3757","position":10,"is_corresponding":false},{"id":451648,"name":"Emmanuel Contreras Guzman","orcid":"0000-0002-1929-3961","position":0,"is_corresponding":true}],"reference_count":0,"raw_metadata":null,"created_at":"2026-07-19T02:56:52.212268Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}