Table 1.

The intestinal mucus layer is a dynamic part of the innate immune system which undergoes quantitative and qualitative changes in response to inflammation. Evidence collected in clinical studies, as well as information gained from animal experiments, have shed light on some of these changes.

	Condition	Effects observed	References
	Crohn's disease	↑Mucus thickness or no change ↓MUC2, MUC3, MUC4, MUC5B, MUC7 MUC5AC and MUC6 present Goblet cell depletion	(145, 146) (155, 156) (155) (144)
	Ulcerative colitis	↓Mucus thickness ↓Glycosylation and sulphation ↑Sialylation ↓MUC2, MUC9, MUC20 ↑MUC1, MUC16 MUC5AC present Goblet cell depletion	(145, 146) (20) (147, 150, 151) (149, 151) (148) (144)
	Colorectal cancer	↑MUC1 ↓MUC2 De novo MUC5AC synthesis	(158) (12, 161) (162, 163)
	Chemical colitis	↑MUC2 (or no change) ↑MUC2 followed by rapid reduction ↑Th1 cytokines (IL-12, TNF-α etc.)	(166) (167) (165)
	Enteric parasitic infection	↑Th2 cytokines (IL-4 and IL-13 etc.) ↑Mucin production/goblet cell hyperplasia ↑Thickness of glycocalyx/MUC4, MUC13, MUC17	(97, 98, 186) (98–103) (103)
	Genetic models:
	1) Muc4−/− 2) Muc2−/− 3) Atg7ΔIEC 4) IL-1rn−/− 5) C1galt1ΔIEC	↓DSS inflammation severity ↑MUC2 and MUC3 ↑DSS inflammation severity/spontaneous colitis ↑DSS inflammation severity ↓MUC2/mucus layer thickness ↑Goblet cell number Spontaneous colitis Microbially breached mucus layer	(170) (169) (179) (174) (153, 180, 181)