Final answer:
True. Lymphopenia can be caused by immunodeficiency disorders such as HIV, DiGeorge syndrome, and SCID, which affect the immune system's ability to produce and maintain an adequate number of lymphocytes.
Step-by-step explanation:
Lymphopenia, which is an abnormally low lymphocyte count, can indeed be caused by immunodeficiency disorders such as HIV, DiGeorge syndrome, and SCID (Severe Combined Immunodeficiency). Lymphocytes are crucial components of the immune system and help in both cell-mediated and humoral immune responses. When these cells are low in number due to an immunodeficiency, the body's ability to fight off infections and certain cancers is compromised. HIV, for example, leads to profound CD4 T-cell lymphopenia, significantly weakening the immune response. SCID, a primary immunodeficiency disorder present from birth, results in an absence of functional B and T cells, causing severe vulnerabilities to infections. Treatments like chemotherapy and exposure to radiation can also cause lymphopenia by destroying lymphocyte populations.