Which antibody class is usually the first one made during a primary response?

1. Mature B cells leaving the bone marrow carry IgM and IgD on their surface, but only IgM is secreted. 2. IgM is usually the first antibody made during a primary response. 3. It consists of five four-chain structures, giving ten identical antigen-binding sites and a large shape that binds many bacterial surfaces well. 4. IgG, IgA and IgE appear only later, once class switching has taken place during the primary response. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 21 "The Lymphatic and Immune System", section 21.4 The Adaptive Immune Response: B-lymphocytes and Antibodies_