The microbiota is an important factor in human development and maintenance of the immune response. Human body harbors 100 trillion commensal microbes, exceeding the number of host cells by more than 10-fold, with a huge amount of genetic information, that is, 100-fold more genes than the human genome. With this enormous pool of genetic information, the microbiota may influence human life at many levels, far beyond host immunity and metabolic functions. Recent studies explaining the interactions between microbiota and the host immune system have revealed the fundamental importance of the microbiome in shaping host immune responses and thereby increasing susceptibility and/or prevention against immune-mediated and/or infectious diseases.

The focus of this special issue is to highlight current status of such relevant research studies, clinical studies, and review articles.

Potential topics include but are not limited to the following:

• Role of human microbiota in maintaining immune homeostasis
• Role of human microbiota in development of specific human diseases, for example, autoimmune diseases and cancers
• Novel approaches and immune-mechanisms induced by human microbiota (probiotics) for prevention and treatment of autoimmune diseases and cancer
• Role of microbiota (specific immune mechanisms) in boosting immunity against the emerging infections (bacterial and viral)