What do low lymphocytes indicate?

Immunodeficiency: lymphocytes are the regulators of our immune system. Low lymphocyte count is less than 500/ mm3 this can be part of a total low white count ( say bone marrow failure or plastic anemia, or after chemotherapy) or it can be caused by connective tissue disease like Lupus. Immunosuppressants, HIV , and Severe acute respiratory distress are viral causes as well. legionella and certain zoonosis can too