Which of the following are considered viral vaccines? (Select all that apply)

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.

A. They have thin walls – Lymphatic vessels have thin walls, similar to veins, which allow for the passage of lymph.
B. They can contract to propel lymph – Lymphatic vessels do have the ability to contract, aided by smooth muscle and valves, which helps propel lymph in the right direction.
C. They transport lymph to the tissues – This statement is incorrect. Lymphatic vessels carry lymph away from the tissues (not to the tissues) and toward lymph nodes and eventually to the bloodstream.
D. They are blind-ended – Lymphatic capillaries are indeed blind-ended, meaning they begin as closed-ended tubes that absorb interstitial fluid from tissues.