Final answer:
IgG is the immunoglobulin with the highest concentration in the bloodstream, playing a vital role in the body's immune defense and providing passive immunity to the developing fetus.
Step-by-step explanation:
The immunoglobulin present in the greatest concentration in the bloodstream is IgG. IgG accounts for about 80% of total serum antibody and is crucial for the body's defense against pathogens. It can penetrate efficiently into tissue spaces and is the only antibody class that can cross the placental barrier during pregnancy to provide passive immunity to the developing fetus. It is also the main antibody of late primary responses and early secondary responses to foreign antigens.
IgG accounts for about 80% of total serum antibody and is the most abundant antibody in human blood. It plays a crucial role in fighting against diseases and can cross the placental barrier, providing passive immunity to the developing fetus during pregnancy.