Medical Laboratory Scientist (MLS) ASCP Practice Exam

Which part of the immunoglobulin molecule is responsible for the differences among immunoglobulin classes?

1. Light chains

2. Heavy chains

3. Variable regions

4. Constant regions

The correct answer is: Heavy chains

The heavy chains of the immunoglobulin molecule are responsible for the differences among immunoglobulin classes, also known as immunoglobulin isotypes. Each class of immunoglobulin (IgA, IgD, IgE, IgG, and IgM) has a distinct heavy chain structure that defines its unique properties, functions, and roles in the immune response. While the variable regions of immunoglobulin molecules are crucial for antigen specificity, which allows antibodies to bind to various antigens, they do not distinguish between the classes of immunoglobulins. On the other hand, the constant regions of the heavy chains are specifically what varies between the classes and determines the immunoglobulin's biological functions, such as how it interacts with immune cells or activates the complement system. In summary, the heavy chains provide the structural basis for the differentiation of immunoglobulin classes, influencing their function and roles in the immune system, thereby making them pivotal in understanding immune responses and antibody actions.