Anti-Inflammatory Neutrophil Functions in the Resolution of Inflammation and Tissue Repair.

Neutrophils are highly abundant circulating leukocytes that are amongst the first cells to be recruited to sites of infection or sterile injury. Their ability to generate and release powerful cytotoxic products ties with their role in host defence from bacterial and fungal infections. Neutrophilic inflammation is tightly regulated to limit the amount of 'bystander injury' caused. Neutrophils were in the past regarded as short-lived, indiscriminate killers of invading microorganisms. However, this view has changed quite dramatically in recent years. Amongst other insights, neutrophils are now recognised to also have important anti-inflammatory functions that are critical for the resolution of inflammation and return to homeostasis. This minireview focusses on anti-inflammatory neutrophil functions, placing a particular focus on recent findings linked to neutrophil cell death, several types of which may be anti-inflammatory (apoptosis, secondary necrosis, and neutrophil extracellular traps). These are discussed together with features that may further promote the clearance of dead cells by efferocytosis and reprogramming of macrophages to promote resolution and repair.

Characterisation of dendritic cell frequency and phenotype in bovine afferent lymph reveals kinetic changes in costimulatory molecule expression.

The bovine afferent lymphatic cannulation model allows collection of large volumes of afferent lymph and provides an opportunity to study lymphatic cells trafficking from the periphery directly ex-vivo. The technique requires surgical intervention, but influence of the procedure or time post-surgery on cells trafficking in the lymph has not been well documented. Here, we measured the volume of lymph and number of cells/mL collected daily over a two week time-course. Animal to animal variability was demonstrated but no consistent changes in lymph volume or cell density were observed in relation to time post-cannulation. Cell populations (dendritic cells, αß T-cells, γδ T-cells and NK cells) were analysed by flow cytometry at 1, 3 and 10 days post-cannulation (DPC) and a reduced percentage of γδ T-cells in afferent lymph was observed at 1 DPC. In addition, cell surface molecule expression by afferent lymphatic dendritic cells (ALDC) was assessed due to the key role of these cells in initiating an adaptive immune response. Co-stimulatory molecules CD80 and CD86 were upregulated by CD172a+ve ALDC early in the time-course, suggesting that the cannulation procedure and duration of experiment may impact the activation state of DCs in the naïve host. This should be considered when analysing the response of these cells to vaccines or pathogens.