Where are the majority of antibodies found?

Immunoglobulins are found in blood and other tissues and fluids. They are made by the plasma cells that are derived from the B cells of the immune system. B cells of the immune system become plasma cells when activated by the binding of a specific antigen on its antibody surfaces. It has been estimated that humans generate about 10 billion different antibodies, each capable of binding a distinct epitope of an antigen.

IgG is the most frequently known antibody it shows mostly in the blood and tissue fluids.

But the othe IgA

IgA is commonly found in the mucous membranes lining around the respiratory and gastrointestinal tracts.