Microbiotal shaping of antigen presenting cell signaling during intestinal immune response

Abstract

Macrophages, dendritic cells (DCs) and to less extent B cells are professional antigen presenting cells (APCs). They sample antigens from the intestinal lumen, process, and present them to cells of the adaptive immune system. While DCs are capable of priming T cell responses, macrophages do polarize the responses. The intestinal lumen contains diverse range of antigens from food proteins, microbiota, and pathogenic microbes that constantly challenge the immune system. While antigens from food proteins and microbiota are not harmful, those from pathogenic microbes are detrimental to the body. The immune system detects both types of antigens and drives immune responses geared at inducing tolerance or reaction to maintain immune homeostasis. Uptake of these antigens is done by the APCs. These cells present antigens to effector cells of the adaptive immune system which generate responses corresponding to particular antigen. The microbiota influences the nature and type of responses generated by APC-activated effector cells by shaping the APC signaling to the adaptive immune system. In a steady state gut environment, the shaping is towards tolerogenic responses while a protective inflammatory reaction results from antigens sampled from harmful microbes. Understanding the interaction between microbiota and APCs in driving immune responses would pave way to improving human and animal health through promotion of maneuvers that maintain immunity.

Keywords: Microbiota, intestine, immunity, dendritic cells, macrophages