Final answer:
IgG is the most abundant immunoglobulin found in the blood, lymph, and intestines. It makes up about 80% of serum antibodies and is critical for fighting diseases, penetrating tissues, and providing passive immunity to fetuses.
Step-by-step explanation:
The most abundant immunoglobulin found in the blood, lymph, and intestines is IgG. IgG is the immunoglobulin with the highest concentration in the blood, accounting for about 80% of all serum antibodies.
IgG stands out due to its ability to be more specific for antigens and it is capable of efficiently penetrating into tissue spaces. It is also unique in that it is the only antibody class that can cross the placental barrier, providing passive immunity to the developing fetus during pregnancy.
While IgA is abundant in seromucous secretions, like saliva and intestinal secretions, and plays a key role in mucosal immunity, it is IgG that is the most prevalent immunoglobulin in the systemic circulation.