Macrophages play a nutritive role in post-metamorphic maturation in Drosophila.

In the body of multicellular organisms, macrophages play an indispensable role in maintaining tissue homeostasis by removing old, apoptotic and damaged cells. In addition, macrophages allow significant remodeling of body plans during embryonic morphogenesis, regeneration and metamorphosis. Although the huge amount of organic matter that must be removed during these processes represents a potential source of nutrients, their further use by the organism has not yet been addressed. Here, we document that, during metamorphosis, Drosophila larval adipose tissue is infiltrated by macrophages, which remove dying adipocytes by efferocytosis and engulf leaking RNA-protein granules and lipids. Consequently, the infiltrating macrophages transiently adopt the adipocyte-like metabolic profile to convert remnants of dying adipocytes to lipoproteins and storage peptides that nutritionally support post-metamorphic development. This process is fundamental for the full maturation of ovaries and the achievement of early fecundity of individuals. Whether macrophages play an analogous role in other situations of apoptotic cell removal remains to be elucidated.

Mass-Spectrometric Identification of Proteins and Pathways Responsible for Fouling on Poly(ethylene glycol) Methacrylate Polymer Brushes.

Prevention of fouling from proteins in blood plasma attracts significant efforts, and great progress is made in identifying surface coatings that display antifouling properties. In particular, poly(ethylene glycol) (PEG) is widely used and dense PEG-like cylindrical brushes of poly[oligo(ethylene glycol) methacrylate] (poly(OEGMA)) can drastically reduce blood plasma fouling. Herein, a comprehensive study of the variation of blood plasma fouling on this surface, including the analysis of the composition of protein deposits on poly(OEGMA) coatings after contact with blood plasma from many different donors, is reported. Correlation between the plasma fouling behavior and protein deposit composition points to the activation of the complement system as the main culprit of dramatically increased and accelerated deposition of blood plasma proteins on this type of antifouling coating, specifically through the classical pathway. These findings are consistent with observations on PEGylated drug carriers and highlight the importance of understanding the potential interactions between antifouling coatings and their environment.

From the fat body to the hemolymph: Profiling tick immune and storage proteins through transcriptomics and proteomics.

Ticks are blood-feeding arachnids that are known to transmit various pathogenic microorganisms to their hosts. During blood feeding, ticks activate their metabolism and immune system to efficiently utilise nutrients from the host's blood and complete the feeding process. In contrast to insects, in which the fat body is known to be a central organ that controls essential metabolic processes and immune defense mechanisms, the function of the fat body in tick physiology is still relatively unexplored. To fill this gap, we sought to uncover the repertoire of genes expressed in the fat body associated with trachea (FB/Tr) by analyzing the transcriptome of individual, partially fed (previtellogenic) Ixodes ricinus females. The resulting catalog of individual mRNA sequences reveals a broad repertoire of transcripts encoding proteins involved in nutrient storage and distribution, as well as components of the tick immune system. To gain a detailed insight into the secretory products of FB/Tr specifically involved in inter-tissue transport and humoral immunity, the transcriptomic data were complemented with the proteome of soluble proteins in the hemolymph of partially fed female ticks. Among these proteins, the hemolipoglyco-carrier proteins were predominant. When comparing immune peptides and proteins from the fat body with those produced by hemocytes, we found that the fat body serves as a unique producer of certain immune components. Finally, time-resolved transcriptional regulation of selected immune transcripts from the FB/Tr was examined in response to experimental challenges with model microbes and analyzed by RT-qPCR. Overall, our data show that the fat body of ticks, similar to insects, is an important metabolic tissue that also plays a remarkable role in immune defense against invading microbes. These findings improve our understanding of tick biology and its impact on the transmission of tick-borne pathogens.