What mechanisms prevent the penetration of microbes into the body?

There are many factors that prevent a microbe from entering the body. Firstly, these are the skin (periodically self-cleaning due to peeling, secretion of sebum by the glands), mucous membranes (also capable of self-cleaning, and they also contain mucin, macrophages and antibodies that capture microbes). Lymph nodes, which contain many immune cells, are also a barrier. There are also immune cells in the blood, and various antibodies are secreted there.