Cells that produce MHC class II molecules are collectively referred to as:

• A. plasma cells
• B. cytotoxic T cells
• C. natural killer (NK) cells
• D. antigen-presenting cells (APCs)

Answer: (D)

Verified step by step guidance

1. Understand the role of MHC class II molecules: These molecules are essential for the immune system, as they present antigens to helper T cells, initiating an immune response.
2. Learn which cells produce MHC class II molecules: MHC class II molecules are produced by specialized immune cells known as antigen-presenting cells (APCs). These include dendritic cells, macrophages, and B cells.
3. Differentiate APCs from other immune cells: Plasma cells, cytotoxic T cells, and natural killer (NK) cells do not produce MHC class II molecules. Plasma cells secrete antibodies, cytotoxic T cells destroy infected cells, and NK cells target cells without MHC molecules.
4. Recognize the function of APCs: APCs process and present antigens on their MHC class II molecules to helper T cells, which then activate other immune cells to respond to the pathogen.
5. Conclude that cells producing MHC class II molecules are antigen-presenting cells (APCs), as they are specifically designed to interact with helper T cells in the immune system.