AIDS (Acquired Immuno Deficiency Syndrome) is caused by HIV (Human Immuno Deficiency Virus). T4− lymphocytes are the principal target cells of HIV. B-lymphoeytes represent about 5-15% of circulating lymphoid tissue and are classically defined by the presence of endogenously produced immunoglobulins (antibody). Leucocytes white blood cell are the nucleated blood corpuscles lacking haemoglobin. Thrombocytes or platelets are small cell like blood borne fragments shed from megakaryocytes in vertebrate bone marrow and essential to normal blood clotting.