T-Cell Immunodeficiency is a condition where the body has a reduced ability to produce or function T-cells, a type of white blood cell crucial for the immune system. T-cells help fight infections and protect the body from diseases. When these cells are deficient, individuals become more susceptible to infections, particularly from viruses and certain bacteria. This immunodeficiency can be caused by genetic disorders, such as Severe Combined Immunodeficiency (SCID), or acquired conditions like HIV/AIDS. Diagnosis often involves blood tests to measure T-cell levels, and treatment may include medications, immunotherapy, or stem cell transplants to restore immune function.