There is external and internal so I'll list th external. The most important is skin then mucus, sweat or secretion, hair, nails and tears which are all part of the integumentary. Some internal defenses are white blood cells and T cells.
HIV tests are used to detect the presence of the human immunodeficiency virus
(HIV) the virus that causes acquired immunodeficiency syndrome (AIDS) in serum, saliva , or urine such tests may antibodies, antigens, or RNA .
