Question

What specialized tissue in the gut wall serves to monitor luminal microflora, what cells are involved in this monitoring, and how do those cells interact with lymphoid cells of the adaptive immune systems?

Answer 1

The human gastrointestinal tract is resided by millions of micro organisms known as gut microbiota that helps in digestion and synthesis of various vitamins.

The gut cells lives in a symbiotic relationship with the gut microbiota and do not evoke a inflammatory response against them. But when a microorganisms that harms the gut enters the GIT it is sensed by specialized tissue present in the gut known as gut associated lymphoid tissue (GALT).
The GALT senses the presence of pathological particle in the gut and stimulates the immune response against it.
The Peyer's patch are the lymphoid follicles present in GALT and contains B and T lymphocytes. Peyer's patch also consists M cells that present the antigen to the antigen presenting cells such as macrophages and dendritic cells. The antigen presenting cells stimulates the B and T lymphocytes. These cells then interact with mesenteric lymph nodes. The lymphoid system gets activated and release lymphocytes in blood that travel to the gut through thoracic duct and destroys the antigen.