Which of the following is NOT true of antibodies?

Antibodies are highly specialized proteins produced by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody consists of two primary regions: the variable region and the constant region. The variable region is responsible for binding specifically to antigens, while the constant region serves a supportive role, determining the mechanism of action and the type of immune response that will be elicited.

In this context, the statement that antibodies have a constant region that binds to an antigen is not accurate. It is the variable region that directly interacts with and specifically binds to antigens. The constant region does not bind to antigens itself; rather, it is involved in other immune functions, such as recruiting other immune cells or molecules once an antigen has been recognized.

The Y-shaped structure of antibodies, their classification into five distinct classes (IgG, IgA, IgM, IgE, and IgD), and their mechanism of neutralization of pathogens are all established truths in immunology. These elements are crucial for understanding how antibodies function within the immune response and their role in providing protection against pathogens.