A germinal center–independent pathway generates unswitched memory B cells early in the primary response

Innate immune responses provoke the accumulation of leukocytes at sites of inflammation. In addition to monocytes and granulocytes, B cells also participate in antimicrobial innate immune responses; however, the mechanisms for accumulation of B cells to sites of inflammation are not well understood. To study B cell accumulation following systemic inflammation, we used a model synthetic ligand that stimulates a specific pattern recognition molecule, nucleotide-binding oligomerization domain–containing protein 1 (Nod1). Upon exposure to Nod1 agonists, both B cells and neutrophils rapidly accumulate within the spleen, and dendritic cells migrate into the periarterial lymphoid sheath. Nod1 stimulation led to a marked increase in several chemokines within the spleen, including CXCL13, CCL2, and CCL20. Whereas the lymphotoxin pathway was critical for the induction of the B cell chemoattractant CXCL13 in response to Nod1 agonists, B cell accumulation within the spleen following Nod1-induced systemic inflammation was independent of the lymphotoxin pathway. In contrast, a CCR6/CCL20 chemokine loop instructed rapid increase of B cells in the spleen in response to systemic administration of Nod1 agonists in a TNF-α–dependent manner. Moreover, CCR6 was required to regulate Nod1-mediated B cell responses. These results reveal a novel mechanism of B cells during inflammation and shed light on how B cells participate in innate immune responses to microbial stimulation.

Section: Discussionsupporting

confidence: 59%

Section: Flow Cytometrymentioning

confidence: 99%

A TNF-α–CCL20–CCR6 Axis Regulates Nod1-Induced B Cell Responses

Paradis

Mindt

Duerr

et al. 2014

“…Memory B cells can display a wide variety of affinities for B cell epitopes present in HA (65-67) because they are developed from both GCdependent and -independent pathways (68,69). Consistent with this development, memory B cells stimulated in vitro secreted HA-binding IgG1 Abs with a wide avidity spectrum after wholevirion vaccination (Fig.…”

Section: Discussionmentioning

confidence: 81%

Whole-Virion Influenza Vaccine Recalls an Early Burst of High-Affinity Memory B Cell Response through TLR Signaling

Onodera

Hosono

Odagiri

et al. 2016

Inactivated influenza vaccines have two formulations, whole- and split-virion types; however, how differential formulations impact their booster effects remain unknown. In this study, we demonstrate that whole-virion vaccines recall two waves of Ab responses, early T cell–independent (TI) and late T cell–dependent responses, whereas split-virion vaccines elicit the late T cell–dependent response only. Notably, higher-affinity Abs with improved neutralizing activity are provided from the early TI response, which emphasizes the important contribution of the formulation-dependent response in the protective immunity. Moreover, we show that the early TI response completely requires B cell–intrinsic TLR7 signaling, which can be delivered through viral RNAs within whole-virion vaccine. Thus, our results indicate that TLR agonists in whole-virion type improve recall Ab responses by directly targeting memory B cells, a finding with important implications for vaccine strategies aimed at the prompt recall of high-affinity neutralizing Abs.

“…To further elucidate germinal center cell commitment to memory B cells or PB/PCs, future studies should incorporate markers that can characterize additional B cell subsets through their intracellular Ig levels, capacity to secrete Ab, or proliferate (56), as well as analyze additional tissues where most Absecreting cells preferentially reside (27,47). In addition, reagents to detect specific BCRs as described for rotavirus, influenza, papillomavirus, and other Ags (27,(76)(77)(78)(79) could be used to reveal SPADE clusters that are enriched with vaccine-specific cells.…”

Section: Discussionmentioning

confidence: 99%

Identification of Vaccine-Altered Circulating B Cell Phenotypes Using Mass Cytometry and a Two-Step Clustering Analysis

Pejoski¹,

Tchitchek²,

Pozo³

et al. 2016

Broadening our understanding of the abundance and phenotype of B cell subsets that are induced or perturbed by exogenous Ags will improve the vaccine evaluation process. Mass cytometry (CyTOF) is being used to increase the number of markers that can be investigated in single cells, and therefore characterize cell phenotype at an unprecedented level. We designed a panel of CyTOF Abs to compare the B cell response in cynomolgus macaques at baseline, and 8 and 28 d after the second homologous immunization with modified vaccinia virus Ankara. The spanning-tree progression analysis of density-normalized events (SPADE) algorithm was used to identify clusters of CD20+ B cells. Our data revealed the phenotypic complexity and diversity of circulating B cells at steady-state and significant vaccine-induced changes in the proportions of some B cell clusters. All SPADE clusters, including those altered quantitatively by vaccination, were characterized phenotypically and compared using double hierarchical clustering. Vaccine-altered clusters composed of previously described subsets including CD27hiCD21lo activated memory and CD27+CD21+ resting memory B cells, and subphenotypes with novel patterns of marker coexpression. The expansion, followed by the contraction, of a single memory B cell SPADE cluster was positively correlated with serum anti-vaccine Ab titers. Similar results were generated by a different algorithm, automatic classification of cellular expression by nonlinear stochastic embedding. In conclusion, we present an in-depth characterization of B cell subphenotypes and proportions, before and after vaccination, using a two-step clustering analysis of CyTOF data, which is suitable for longitudinal studies and B cell subsets and biomarkers discovery.