What is the site where an antigen attaches itself called?

The correct answer to the question is "receptor site." This term refers to specific locations on a cell or protein where an antigen can bind. Receptor sites are crucial for the immune response, as they allow cells to recognize and respond to foreign substances, including pathogens like viruses and bacteria.

When an antigen encounters a receptor site, it can trigger a series of biological responses, often leading to the activation of immune cells to target and eliminate the foreign invader. This interaction is fundamental to the functioning of the immune system, helping to identify and respond to threats.

In the context of the question, options such as "immunocyte" and "receptorcyte" do not specifically describe the binding location of an antigen. Instead, they refer to types of cells (like immune cells) involved in the immune response rather than the sites where antigens bind. "Antigen site" lacks specificity and is not commonly used terminology in immunology to denote where an antigen attaches.