An activated monocyte is also known as a:

A. Most type-1 reactions are allergic: This statement is accurate. Type-1 hypersensitivity reactions are typically associated with allergies. When a person is exposed to a specific allergen (like pollen or certain foods), their immune system overreacts, leading to various symptoms, from mild to severe.

B. It is mediated by IgA: This statement is incorrect. Type-1 hypersensitivity reactions are primarily mediated by immunoglobulin E (IgE) antibodies. When these antibodies bind to allergens, they trigger the release of histamine and other chemicals, causing allergic symptoms.

C. It never contributes to autoimmune diseases: This statement is incorrect. While type-1 hypersensitivity reactions are often associated with allergies, they are distinct from autoimmune diseases. In autoimmune diseases, the immune system mistakenly attacks the body's own cells and tissues, which is a different mechanism from hypersensitivity reactions.

D. Most occur against medications: This statement is not entirely accurate. While some type-1 hypersensitivity reactions can be triggered by medications (like penicillin), they can also be caused by various other allergens such as pollen, animal dander, insect venom, and certain foods. The prevalence of medication-induced type-1 reactions varies, and it's not accurate to say that most occur against medications.

A. Macrophage: This is the correct answer. An activated monocyte is also known as a macrophage. Monocytes are white blood cells that can mature into macrophages when they move into tissues. Macrophages play a crucial role in the immune system by phagocytosing (engulfing and digesting) pathogens and cellular debris.

B. Lymphocyte: Lymphocytes are another type of white blood cell that plays a central role in the immune system. They include B cells, T cells, and natural killer cells. Lymphocytes are primarily involved in adaptive immune responses, such as antibody production (B cells) and cell-mediated immune responses (T cells).

C. Plasma Cell: Plasma cells are a type of B cell that produces antibodies (immunoglobulins). They are involved in the adaptive immune response, specifically in the production of antibodies that target specific pathogens.

D. Polymorphonuclear Leukocyte: This term typically refers to a group of white blood cells that have a multi-lobed nucleus. Neutrophils, eosinophils, and basophils are examples of polymorphonuclear leukocytes. They are involved in innate immune responses, including the phagocytosis of pathogens.