Which immune response primarily involves IgM production?

The primary immune response is characterized by the initial production of antibodies, primarily IgM, in response to a new antigen. When the immune system first encounters a pathogen, naïve B cells become activated and differentiate into plasma cells that produce IgM antibodies as their first line of response. This initial phase typically takes longer, from a few days to a couple of weeks, before antibody levels peak.

In contrast, the secondary immune response involves memory B cells that have been previously activated and are capable of quickly producing higher affinity antibodies, mainly of the IgG class, upon re-exposure to the same antigen. While both the humoral and cell-mediated responses are important components of the adaptive immune system, the humoral response refers broadly to antibody-mediated immunity and involves different antibody classes beyond just IgM. Cell-mediated responses, on the other hand, primarily involve T cells and do not directly involve IgM production. Thus, focusing specifically on IgM, the primary response is correctly identified as the phase where its production is most pronounced.