Human memory B cells (MBCs) are generated and diversified in secondary lymphoid tissues throughout the organism. A paired immunoglobulin (Ig)-gene repertoire analysis of peripheral blood (PB) and splenic MBCs from infant, adult, and elderly humans revealed that throughout life, circulating MBCs are comprehensively archived in the spleen. Archive MBC clones are systematically preserved and uncoupled from class-switching. Clonality in the spleen increases steadily, but boosts at midlife, thereby outcompeting small clones. The splenic marginal zone (sMZ) represents a primed MBC compartment, generated from a stochastic exchange within the archive memory pool. This is supported by functional assays, showing that PB and splenic CD21+ MBCs acquire transient CD21high expression upon NOTCH2-stimulation. Our study provides insight that the human MBC system in PB and spleen is composed of three interwoven compartments: the dynamic relationship of circulating, archive, and its subset of primed (sMZ) memory changes with age, thereby contributing to immune aging.

Introduction: The medicinal plant marshmallow Althaea officinalis L. (A. officinalis), is used for the treatment of cough since centuries. Application of medicinal extracts of marshmallow roots shows immediate effects like a protective film on the inflamed mucosa. Because the soothing layer reduce irritation of the mucous system, a faster regeneration is supported by defense mechanisms required to protect the respiratory tract from environmental injury. Macrophages (M), which belong to a group of multipurpose defensive cells, provide the first line of defense against mucosal invasive pathogens. The present study was performed to investigate, whether the herbal medicinal product has anti-inflammatory or anti-oxidative effects on pro-inflammatorily activated M or after oxidative stress induction. Special attention should be payed to elucidate the effects of A. officinalis on the mechanism of intracellular defense as well as on migratory capacity of the M. Results: Treatment of PMA-differentiated human THP-1 M with Phytohustil R increased their viability without affecting the cell number. Phytohustil R or root extracts of A. officinalis (REAo)-an active component of Phytohustil R-were able to protect human M against H 2 O 2-induced cytotoxicity and H 2 O 2-induced ROS production. Phytohustil R , REAo or diclofenac used as anti-inflammatory reference substance, inhibited the LPS-induced release of tumor necrosis factor-alpha (TNF-α) as well as of IL6 in M. Treatment with Phytohustil R , its excipients or REAo did not impair the mitochondrial membrane potential (MMP). Finally, Phytohustil R and REAo activated the migratory capacity of M. Conclusion: The present in vitro investigations indicate protective, i.e., anti-oxidative and anti-inflammatory effects of REAo and Phytohustil R , additionally improving the migratory capacity of M. These antiinflammatory effects were similar or even better than diclofenac. Thus, our data support and may explain the positive effect of Phytohustil R observed in patients during the therapy of inflamed buccal mucosal membranes or treatment of cough.

Neonatal and infant immune responses are characterized by a limited capability to generate protective Ab titers and memory B cells as seen in adults. Multiple studies support an immature or even impaired character of umbilical cord blood (UCB) B cells themselves. In this study, we provide a comprehensive molecular and functional comparison of B cell subsets from UCB and adult peripheral blood. Most UCB B cells have a mature, naive B cell phenotype as seen in adults. The UCB Ig repertoire is highly variable but interindividually conserved, as BCR clonotypes are frequently shared between neonates. Furthermore, UCB B cells show a distinct transcriptional program that confers accelerated responsiveness to stimulation and facilitated IgA class switching. Stimulation drives extensive differentiation into Ab-secreting cells, presumably limiting memory B cell formation. Humanized mice suggest that the distinctness of UCB versus adult B cells is already reflected by the developmental program of hematopoietic precursors, arguing for a layered B-1/B-2 lineage system as in mice, albeit our findings suggest only partial comparability to murine B-1 cells. Our study shows that UCB B cells are not immature or impaired but differ from their adult mature counterpart in a conserved BCR repertoire, efficient IgA class switching, and accelerated, likely transient response dynamics.

SUMMARYThe human infant B cell system is considered premature or impaired. Here we show that neonates have mature and fully functional B cell subsets as seen in adults, albeit with distinct transcriptional programs providing accelerated responsiveness to T cell independent and T cell dependent stimulation and facilitated IgA class switching. Stimulation drives extensive differentiation into antibody secreting cells, thereby presumably limiting memory B cell formation. The neonatal Ig-repertoire is highly variable, but conserved, showing 8% recurrent B cell receptor (BCR) clonotypes shared between neonates. Our study demonstrates that neonatal B cells are neither premature nor impaired, but differ from their adult counterpart in a conserved BCR repertoire and rapid but transient response dynamics. These properties may account for the sensitivity of neonates to infections and limited effectivity of vaccination strategies. Finally, our findings have implications for a limited comparability of mouse models to human infant B cell immunity.

Single-cell RNAseq/VDJseq of tumor cells and normal residual B (NRB) cells from peripheral blood of chronic lymphocytic leukemia (CLL) patients identified three distinct tumor subsets according to phenotype, transcriptome, and immunoglobulin-V-gene (IgV)-mutations. Two major subsets share a typical CLL phenotype but differ in signaling, metabolism and cell cycle control, indicating that the circulating CLL pool is shaped by two states of activity. The third CLL subset shows the phenotype, proliferation capacity and extensive IgV-mutation diversity of normal CD5+ memory B cells. This previously unrecognized CLL tumor subset, which intermingles with NRB cells, was confirmed in 33 IgV-mutated (M-CLL) and IgV-unmutated (U-CLL) cases. Longitudinal IgV-mutation phylogenetics suggest that these NRB-associated CLL cells are generated pathogenetically early, mostly in germinal center reactions, and archive the individual IgV-diversification program, which is conserved throughout CLL course. Our study suggests that diversity is established early in CLL, that each tumor is composed of multiple subclonal expansions, and subclonal evolution can be depicted by IgV mutation phylogenetics.