Inclusion Criteria:

For all groups:

• Written informed consent from parent(s)/legal guardian(s);
• Sex: Males and Females;
• Age: ≥2 years and <18 years.

For study group 1:

- Subjects with suspected or confirmed IBD diagnosis.

For study group 2:

- Subjects with rectal bleeding w/o inflammatory disorders of the gastrointestinal tract.

For study group 3:

• Written consent for participation to TIGET09 study protocol;
• healthy subjects, without known immunodeficiencies, autoimmune, inflammatory or genetic diseases, undergoing genetic, hematological, hematochemical, or HLA compatibility screenings and participating in the TIGET09 study protocol (Title: "Collection of biological samples for the study of blood cells and their microenvironment, and for the development of novel therapeutic approaches for genetic diseases and cancer").

Exclusion Criteria:

For all groups:

• Refusal or inability of the parent(s) or legal guardian(s) to provide written informed consent;
• Age: <2 years and ≥18 years;
• Presence of any medical, psychiatric, or clinical condition that, in the opinion of the clinician, may interfere with participation in the study or interpretation of the study results;

For study group 1:

- patients without IBD diagnosis or suspect;

For study group 2:

- Subjects without rectal bleeding or with known inflammatory/autoimmune disorders of the gastrointestinal tract.

For all groups:

• Refusal or inability of the parent(s) or legal guardian(s) to provide written informed consent;
• Age: <2 years and ≥18 years;
• Presence of any medical, psychiatric, or clinical condition that, in the opinion of the clinician, may interfere with participation in the study or interpretation of the study results;

For study group 1:

- patients without IBD diagnosis or suspect;

For study group 2:

- Subjects without rectal bleeding or with known inflammatory/autoimmune disorders of the gastrointestinal tract.

For study group 3:

• Lack of written consent for participation to TIGET09 study protocol;
• patients belonging to study groups 1 and 2; patients with immunodeficiencies, autoimmune, inflammatory or genetic diseases;
• subjects with signs of systemic inflammation.