Graphical Abstract Highlights d NK cell-activating antibodies are selectively transferred across the placenta d Digalactosylated Fc glycans are preferentially transferred across the placenta d Digalactosylated antibodies bind more effectively to FcRn and FCGR3A d Although immature, neonatal NK cells are highly responsive to immune complexes SUMMARY Despite the worldwide success of vaccination, newborns remain vulnerable to infections. While neonatal vaccination has been hampered by maternal antibody-mediated dampening of immune responses, enhanced regulatory and tolerogenic mechanisms, and immune system immaturity, maternal pre-natal immunization aims to boost neonatal immunity via antibody transfer to the fetus. However, emerging data suggest that antibodies are not transferred equally across the placenta. To understand this, we used systems serology to define Fc features associated with antibody transfer. The Fc-profile of neonatal and maternal antibodies differed, skewed toward natural killer (NK) cell-activating antibodies.This selective transfer was linked to digalactosylated Fc-glycans that selectively bind FcRn and FCGR3A, resulting in transfer of antibodies able to efficiently leverage innate immune cells present at birth. Given emerging data that vaccination may direct antibody glycosylation, our study provides insights for the development of next-generation maternal vaccines designed to elicit antibodies that will most effectively aid neonates. Antibodies against pertussis derived filamentous hemagglutinin (FHA), pertactin (PTN), fimbriae (FIM), and pertussis toxin (PTX) antigens were compared in 14 mother:cord pairs. (A) The flow cytometric plots depict the gating strategy for antibody dependent cellular phagocytosis (ADCP). (B) The connected dot-plot shows the phagocytic activity across mother:cord pairs. (C) The box-and-whisker plot shows the transfer ratio of ADCP. The dotted line indicates a 100% transfer efficiency (equivalent levels across both compartments). (D) The flow plots highlight the gating strategy for antibody dependent neutrophil phagocytosis (ADNP). (E) The dot-plot shows the relationship between ADNP activity across mother:cord pairs for each antigen-specificity. (F) The whisker plots show the transfer ratio for ADNP. (G) The flow plots highlighting the gating strategy for the NK cell activation assay. (H-J) The dot-line plots show NK-dependent degranulation plotted as the percentage of NK cells positive for CD107a (H), IFNg (I), and MIP-1b (J). (K-M) The whisker plots depict the transfer ratio across the three NK cell activation markers, CD107a (K), IFNg (L), and MIP-1b (M).

The mucus barrier is selectively permeable to a wide variety of molecules, proteins, and cells, and establishes gradients of these particulates to influence the uptake of nutrients, the defense against pathogens, and the delivery of drugs. Despite its importance for health and disease, the criteria that govern transport through the mucus barrier are largely unknown. Studies with uniformly functionalized nanoparticles have provided critical information about the relevance of particle size and net charge for mucus transport. However, these particles lack the detailed spatial arrangements of charge found in natural mucus-interacting substrates, such as certain viruses, which may have important consequences for transport through the mucus barrier. Using a novel, to our knowledge, microfluidic design that enables us to measure real-time transport gradients inside a hydrogel of mucins, the gel-forming glycoprotein component of mucus, we show that two peptides with the same net charge, but different charge arrangements, exhibit fundamentally different transport behaviors. Specifically, we show that certain configurations of positive and negative charges result in enhanced uptake into a mucin barrier, a remarkable effect that is not observed with either charge alone. Moreover, we show that the ionic strength within the mucin barrier strongly influences transport specificity, and that this effect depends on the detailed spatial arrangement of charge. These findings suggest that spatial charge distribution is a critical parameter to modulate transport through mucin-based barriers, and have concrete implications for the prediction of mucosal passage, and the design of drug delivery vehicles with tunable transport properties.

We introduce an integrated microfluidic device consisting of a biomolecule concentrator and a microdroplet generator, which enhances the limited sensitivity of low-abundance enzyme assays by concentrating biomolecules before encapsulating them into droplet microreactors. We used this platform to detect ultra low levels of matrix metalloproteinases (MMPs) from diluted cellular supernatant and showed that it significantly (∼10-fold) reduced the time required to complete the assay and the sample volume used.

Single-cell analysis provides information critical to understanding key disease processes that are characterized by significant cellular heterogeneity. Few current methods allow single-cell measurement without removing cells from the context of interest, which not only destroys contextual information but also may perturb the process under study. Here we present a microfluidic probe that lyses single adherent cells from standard tissue culture and captures the contents to perform single-cell biochemical assays. We use this probe to measure kinase and housekeeping protein activities, separately or simultaneously, from single human hepatocellular carcinoma cells in adherent culture. This tool has the valuable ability to perform measurements that clarify connections between extracellular context, signals and responses, especially in cases where only a few cells exhibit a characteristic of interest.