A novel cryopreservation and biobanking strategy to study lymphoid tissue stromal cells in human disease.

Nonhematopoietic lymph node stromal cells (LNSCs) regulate lymphocyte trafficking, survival, and function for key roles in host defense, autoimmunity, alloimmunity, and lymphoproliferative disorders. However, the study of LNSCs in human diseases is complicated by a dependence on viable lymphoid tissues, which are most often excised prior to establishment of a specific diagnosis. Here, we demonstrate that cryopreservation can be used to bank lymphoid tissue for the study of LNSCs in human disease. Using human tonsils and lymph nodes (LN), lymphoid tissue fragments were cryopreserved for subsequent enzymatic digestion and recovery of viable nonhematopoietic cells. Flow cytometry and single-cell transcriptomics identified comparable proportions of LN stromal cell types in fresh and cryopreserved tissue. Moreover, cryopreservation had little effect on transcriptional profiles, which showed significant overlap between tonsils and LN. The presence and spatial distribution of transcriptionally defined cell types were confirmed by in situ analyses. Our broadly applicable approach promises to greatly enable research into the roles of LNSCs in human disease.

A novel cryopreservation and biobanking strategy to study lymphoid tissue stromal cells in human disease.

Non-hematopoietic lymph node stromal cells (LNSCs) regulate lymphocyte trafficking, survival, and function for key roles in host defense, autoimmunity, alloimmunity, and lymphoproliferative disorders. However, study of LNSCs in human diseases is complicated by a dependence on viable lymphoid tissues, which are most often excised prior to establishment of a specific diagnosis. Here, we demonstrate that cryopreservation can be used to bank lymphoid tissue for the study of LNSCs in human disease. Using human tonsils, lymphoid tissue fragments were cryopreserved for subsequent enzymatic digestion and recovery of viable non-hematopoietic cells. Flow cytometry and single-cell transcriptomics identified comparable proportions of LNSC cell types in fresh and cryopreserved tissue. Moreover, cryopreservation had little effect on transcriptional profiles, which showed significant overlap between tonsils and lymph nodes. The presence and spatial distribution of transcriptionally defined cell types was confirmed by in situ analyses. Our broadly applicable approach promises to greatly enable research into the roles of LNSC in human disease.

Lipid nanoparticles enhance the efficacy of mRNA and protein subunit vaccines by inducing robust T follicular helper cell and humoral responses.

Adjuvants are critical for improving the quality and magnitude of adaptive immune responses to vaccination. Lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA vaccines have shown great efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the mechanism of action of this vaccine platform is not well-characterized. Using influenza virus and SARS-CoV-2 mRNA and protein subunit vaccines, we demonstrated that our LNP formulation has intrinsic adjuvant activity that promotes induction of strong T follicular helper cell, germinal center B cell, long-lived plasma cell, and memory B cell responses that are associated with durable and protective antibodies in mice. Comparative experiments demonstrated that this LNP formulation outperformed a widely used MF59-like adjuvant, AddaVax. The adjuvant activity of the LNP relies on the ionizable lipid component and on IL-6 cytokine induction but not on MyD88- or MAVS-dependent sensing of LNPs. Our study identified LNPs as a versatile adjuvant that enhances the efficacy of traditional and next-generation vaccine platforms.

IgA Plasma Cells Are Long-Lived Residents of Gut and Bone Marrow That Express Isotype- and Tissue-Specific Gene Expression Patterns.

Antibody secreting plasma cells are made in response to a variety of pathogenic and commensal microbes. While all plasma cells express a core gene transcription program that allows them to secrete large quantities of immunoglobulin, unique transcriptional profiles are linked to plasma cells expressing different antibody isotypes. IgA expressing plasma cells are generally thought of as short-lived in mucosal tissues and they have been understudied in systemic sites like the bone marrow. We find that IgA+ plasma cells in both the small intestine lamina propria and the bone marrow are long-lived and transcriptionally related compared to IgG and IgM expressing bone marrow plasma cells. IgA+ plasma cells show signs of shared clonality between the gut and bone marrow, but they do not recirculate at a significant rate and are found within bone marrow plasma cells niches. These data suggest that systemic and mucosal IgA+ plasma cells are from a common source, but they do not migrate between tissues. However, comparison of the plasma cells from the small intestine lamina propria to the bone marrow demonstrate a tissue specific gene transcription program. Understanding how these tissue specific gene networks are regulated in plasma cells could lead to increased understanding of the induction of mucosal versus systemic antibody responses and improve vaccine design.

Commensal Microbes Induce Serum IgA Responses that Protect against Polymicrobial Sepsis.

Serum immunoglobulin A (IgA) antibodies are readily detected in mice and people, but the mechanisms underlying the induction of serum IgA and its role in host protection remain uncertain. We report that select commensal bacteria induce several facets of systemic IgA-mediated immunity. Exposing conventional mice to a unique but natural microflora that included several members of the Proteobacteria phylum led to T cell-dependent increases in serum IgA levels and the induction of large numbers of IgA-secreting plasma cells in the bone marrow. The resulting serum IgA bound to a restricted collection of bacterial taxa, and antigen-specific serum IgA antibodies were readily induced after intestinal colonization with the commensal bacterium Helicobacter muridarum. Finally, movement to a Proteobacteria-rich microbiota led to serum IgA-mediated resistance to polymicrobial sepsis. We conclude that commensal microbes overtly influence the serum IgA repertoire, resulting in constitutive protection against bacterial sepsis.