The article discusses the concept of dysbiosis, which refers to the disruption of the normal microbial community in the human body, and its impact on host immunity and disease. Dysbiosis can lead to improper training of the immune system by the microbiota, contributing to the development of immune-mediated diseases such as inflammatory bowel disease (IBD), multiple sclerosis (MS), type 1 diabetes (T1D), allergies, and asthma. The article highlights three main types of dysbiosis: loss of beneficial microbial organisms, expansion of pathobionts, and loss of microbial diversity. Each type is associated with specific mechanisms that affect host health and immune responses. For example, loss of beneficial microbes can compromise the development of regulatory T cells (Tregs), which are crucial for maintaining immune homeostasis. Expansion of pathobionts, such as Proteobacteria, can contribute to inflammation and disease progression. Loss of microbial diversity can also lead to a loss of protective immune functions. The article emphasizes the importance of restoring a healthy microbial community, referred to as rebiosis, to treat complex immune diseases. This can be achieved through various methods, including fecal microbiota transplantation (FMT) and the use of probiotics and prebiotics. The review underscores the need for further research to understand the complex interactions between the microbiota and the host, and to develop effective therapies that can manipulate these interactions to improve health.The article discusses the concept of dysbiosis, which refers to the disruption of the normal microbial community in the human body, and its impact on host immunity and disease. Dysbiosis can lead to improper training of the immune system by the microbiota, contributing to the development of immune-mediated diseases such as inflammatory bowel disease (IBD), multiple sclerosis (MS), type 1 diabetes (T1D), allergies, and asthma. The article highlights three main types of dysbiosis: loss of beneficial microbial organisms, expansion of pathobionts, and loss of microbial diversity. Each type is associated with specific mechanisms that affect host health and immune responses. For example, loss of beneficial microbes can compromise the development of regulatory T cells (Tregs), which are crucial for maintaining immune homeostasis. Expansion of pathobionts, such as Proteobacteria, can contribute to inflammation and disease progression. Loss of microbial diversity can also lead to a loss of protective immune functions. The article emphasizes the importance of restoring a healthy microbial community, referred to as rebiosis, to treat complex immune diseases. This can be achieved through various methods, including fecal microbiota transplantation (FMT) and the use of probiotics and prebiotics. The review underscores the need for further research to understand the complex interactions between the microbiota and the host, and to develop effective therapies that can manipulate these interactions to improve health.