The course of Crohn's disease (CD) varies considerably between patients, but reliable prognostic markers are not available in clinical practice. Even though several parameters have been associated with prognosis in CD-including clinical features, serology and genetic variants-none are sufficient to guide therapy in clinical practice. Trying to find out the mechanisms influencing the effectiveness of treatments and develop a personalized therapy is an urgent problem in the era of biologics as the investigators now have a growing armamentarium of IBD therapies. Several scientists found that the levels of T cells subsets ratio and inflammation cytokines were significantly increased in the intestinal mucosa and serum in active IBD patients, whereas mucosal innate lymph cells had specific effects in inflammation. However the studies about the differences of lymph cell levels between subgroups of IBD patients and their relationships with effectiveness of treatments are relatively rare. Based on above, the investigators plan to recruit patients diagnosed and suspicious of Crohn's disease and a group of diseases in differential diagnosis of CD to keep track of their disease characteristics, therapy and response, collect their blood sample at specific points of time, to investigate the mechanisms of heterogeneity of therapy effectiveness.

Inclusion Criteria:

• Newly diagnosed or Previously diagnosed of Crohn's disease according to 2010 WGO criteria for Crohn's disease
• Aged 14-80 years old.

Exclusion Criteria:

• History of malignancy
• Pregnant/breastfeeding at screening
• Other serious medical or psychiatric illness.
• Unable to comply with protocol requirements

Patients aged 14-80 years old, newly diagnosed or previously diagnosed of Crohn's disease according to 2010 WGO criteria for Crohn's disease were recruited from a specialist IBD clinic.