Interactions between Intestinal Microflora/Probiotics and the Immune System

Table 1

Elements of intestinal mucosal immunity.

Structures	Constitution	Effect and mechanism
Lumen	Commensal bacteria	Competitively inhibit pathogenic bacteria
		Produce antimicrobial substances
	Mucus	Traps pathogens
		Prevents access to epithelial layer
		Contains secretory immunoglobulin A
	Glycocalyx	Provides physical barrier
Epithelial layer	Enterocytes	Connected by tight junctions
		Surface TLRs induce secretion of proinflammatory chemokines, cytokines, and growth factors
		Capture some antigens
	Goblet cells	Secrete mucus
	Paneth cells	Produce defensins and antibiotic substances
	Enteroendocrine cells	Produce neuroendocrine mediators
	γδiIELs	Promote αβiIEL activation through cytokine and chemokine secretion
		Produce antimicrobial effectors and protect against pathogens
		Prevent inflammation-induced epithelium damage
	M cells	Capture and transport antigen
Lamina propria	αβT cells, B cells, DCs, and other APCs	Initiate adaptive immune responses in lymphoid follicles
	Treg cells	Suppress activation and effector function of immune cells