The Shulman Lab

Tumor-infiltrating B cells have emerged in recent years as key markers of patient prognosis and responsiveness to immunotherapy. Recent technical advances, such as single-cell RNA sequencing and B cell receptor immune profiling, revealed diverse subsets and the immunoglobulin landscape of B cells located within human tumors. Secreted antibodies in solid tumors exhibit multiple effector functions, with the potential to significantly impact distinct immune responses, clinical outcomes, and patient survival. Nonetheless, a few studies examine the tumor reactivity and specificity of these immunoglobulins. Here we describe our current methodology for retrieving single B cells from human primary solid tumors for single-cell RNA sequencing followed by computational analysis to identify B cell subpopulations and immunoglobulin receptor repertoires. Furthermore, we provide a technique for evaluating and quantifying the tumor-binding capabilities of expressed antibodies. This approach holds promise for future immunotherapies and enhances our understanding of their potential clinical applications.

The establishment of long-lasting immunity against pathogens is facilitated by the germinal center (GC) reaction, during which B cells increase their antibody affinity and differentiate into antibody-secreting cells (ASC) and memory cells. These events involve modifications in chromatin packaging that orchestrate the profound restructuring of gene expression networks that determine cell fate. While several chromatin remodelers were implicated in lymphocyte functions, less is known about SMARCA5. Here, using ribosomal pull-down for analyzing translated genes in GC B cells, coupled with functional experiments in mice, we identified SMARCA5 as a key chromatin remodeler in B cells. While the naive B cell compartment remained unaffected following conditional depletion of Smarca5, effective proliferation during B cell activation, immunoglobulin class switching, and as a result GC formation and ASC differentiation were impaired. Single-cell multiomic sequencing analyses revealed that SMARCA5 is crucial for facilitating the transcriptional modifications and genomic accessibility of genes that support B cell activation and differentiation. These findings offer novel insights into the functions of SMARCA5, which can be targeted in various human pathologies.

Nasal vaccination elicits a humoral immune response that provides protection from airborne pathogens¹, yet the origins and specific immune niches of antigen-specific IgA-secreting cells in the upper airways are unclear². Here we define nasal glandular acinar structures and the turbinates as immunological niches that recruit IgA-secreting plasma cells from the nasal-associated lymphoid tissues (NALTs)³. Using intact organ imaging, we demonstrate that nasal vaccination induces B cell expansion in the subepithelial dome of the NALT, followed by invasion into commensal-bacteria-driven chronic germinal centres in a T cell-dependent manner. Initiation of the germinal centre response in the NALT requires pre-expansion of antigen-specific T cells, which interact with cognate B cells in interfollicular regions. NALT ablation and blockade of PSGL-1, which mediates interactions with endothelial cell selectins, demonstrated that NALT-derived IgA-expressing B cells home to the turbinate region through the circulation, where they are positioned primarily around glandular acinar structures. CCL28 expression was increased in the turbinates in response to vaccination and promoted homing of IgA⁺ B cells to this site. Thus, in response to nasal vaccination, the glandular acini and turbinates provide immunological niches that host NALT-derived IgA-secreting cells. These cellular events could be manipulated in vaccine design or in the treatment of upper airway allergic responses.