Which of the following refer to passive immunity? (select all that apply)

A. Lacteals are specialized lymphatic capillaries located in the villi of the small intestine. They absorb digested fats (in the form of chylomicrons) and transport them into the lymphatic system, eventually entering the bloodstream.
B. Peyer patches are clusters of lymphoid tissue found in the small intestine, important for immune surveillance, but they are not involved in fat absorption.
C. Kupffer cells are specialized macrophages in the liver that filter blood, not involved in lymphatic fat transport.
D. Lymph capillaries generally collect interstitial fluid to form lymph, but lacteals are the specific type of lymph capillary responsible for absorbing dietary fats.

A. An antigen is any foreign substance (such as bacteria, viruses, or toxins) that triggers an immune response in the body. The immune system recognizes and responds to antigens, typically by producing antibodies.
B. Inflammation is a response of the body to injury or infection, characterized by redness, heat, swelling, and pain, but it is not a foreign substance itself.
C. An allergen is a specific type of antigen that causes an allergic reaction. While all allergens are antigens, not all antigens are allergens.
D. A lymphocyte is a type of white blood cell involved in the immune response, but it is not a foreign substance. Lymphocytes help recognize and respond to antigens.