What is the first class of antibody that plasma cells release?

• A. IgA
• B. IgD
• C. IgG
• D. IgM

Answer: (D)

The first class of antibody that plasma cells release is IgM. This antibody serves as the initial response to an antigen and is crucial during the early stages of an immune response. When B cells are activated by an antigen, they differentiate into plasma cells, which are responsible for producing antibodies. IgM is typically produced first before any class-switching to other antibodies occurs, making it essential for primary immune responses.

IgM plays a pivotal role in agglutination and activating the complement system, contributing to the body's ability to eliminate pathogens effectively during this early phase of infection. Its pentameric structure, consisting of five antibody units, enhances its ability to bind multiple antigens, increasing its effectiveness in neutralizing foreign invaders and recruiting other immune cells to the site of infection. This distinguishes IgM as the primary antibody that marks the beginning of an adaptive immune response.