In infectious mononucleosis, which antibodies does the Monospot test detect in the early weeks after infection?

The Monospot test is designed to detect heterophile antibodies, which are typically Immunoglobulin M (IgM) antibodies produced during the early phase of infectious mononucleosis, primarily due to Epstein-Barr virus (EBV) infection. In the initial weeks following infection, the immune response generates these antibodies rapidly, making them a reliable indicator of recent infection.

IgM antibodies are among the first antibodies produced in response to an infection, providing a crucial early immune response. Their presence confirms that the body is reacting to the infection. In contrast, IgG antibodies develop later and indicate past infection or immunity, while IgA and IgE play different roles in immune response and are not typically assessed in the context of infectious mononucleosis using the Monospot test. Thus, detecting IgM in this scenario is essential for confirming early-stage infectious mononucleosis.