Innate immune system

The innate immune system is the first immunological defence mechanism against environmental factors, such as bacteria, viruses, fungi, and toxins It acts non-specifically and is activated immediately in response to contact with environmental factors. 
Innate immunity comprises different barriers:
1.    anatomic barriers (skin and mucous membranes);
2.    physiologic barriers (fever, low pH, and chemical mediators);
3.    phagocytic and endocytic barriers (cells internalize foreign substances/pathogens to eliminate them), and 
4.    inflammatory barriers.
Immune cells of the innate immune system (phagocytes, mast cells, basophils and eosinophils) act mutually with immune modulatory molecules (eicosanoids, complement system, proteins) and mediate acute immune responses, such as inflammation, immune cell coordination, and opsonisation. In addition, it contributes to prevention of infections (Marshall et al., 2018).