Macrophages and Neutrophils: Regulation of the Inflammatory Microenvironment in Autoimmunity and Cancer

Macrophages and neutrophils are phagocytes that play major roles in the onset and maintenance of many diseases. These two cell types that belong to the innate immune system are extremely plastic and can move between different modes of activation upon cues received from their immediate microenvironment [1–3]. Once activated, these cells secrete myriad of mediators that shape and regulate the microenvironment, as well as other immune cells, such that this continuous dialogue determines the direction of the immune response and its outcome [4]. This is highlighted in this issue as we focus on the role of macrophages and neutrophils in both cancer and autoimmune diseases. Although these are different diseases, with opposing pathophysiologies and activation of the immune system, some similarities do exist [5]. By comparing these two cell populations in cancer and autoimmune diseases, in the context of their respective microenvironment, we try to examine whether there are similar attributes that could potentially be exploited as new therapeutic strategies. Most of the manuscripts in this issue are dedicated to cancer and the tumor microenvironment (TME), reflecting the abundance of information on macrophages, and the now growing recognition of the role that neutrophils play in the cancerous context. In contrast, the role that both macrophage and neutrophils play in autoimmune diseases is only beginning to emerge and merits more investigation.