Antibodies 

• IgG: The most abundant antibody in blood, providing long-term protection and passive immunity to the fetus.
• IgA: The main antibody found in mucosal secretions, protecting respiratory and gastrointestinal surfaces.
• IgM: The first antibody produced during an acute infection, indicating recent exposure.
• IgE: An antibody involved in allergic reactions and defense against parasites.
• IgD: A regulatory antibody involved in B-cell activation, present in low concentrations.