T lymphocytes, especially CD4+ T cells, have been implicated in the development of sarcoidosis (45) and other diseases such as gastrointestinal diseases (e.g., celiac disease, IBD), endocrine diseases (e.g., T1DM), liver diseases (e.g., primary biliary cholangitis), neurological diseases (e.g., multiple sclerosis), and cutaneous diseases (e.g., psoriasis) (46–48). Here, CD4 is linked to gastrointestinal disease.