ADA and infectious mononucleosis: This enzyme regulates how these metabolites affect vascular, neurological, and immune systems in a physiologically significant way [30]. ADA is crucial for the development and multiplication of lymphocytes, especially T-cells. ADA activity is elevated in disorders such as typhoid fever, infectious mononucleosis, liver disease, sarcoidosis, leukemia, brucellosis, acute pneumonia, RA, malignancies, and tuberculosis that are linked to cellular system activation [31].