Which immunoglobulin is predominant in body secretions?

The predominant immunoglobulin found in body secretions is immunoglobulin A (IgA). It plays a crucial role in mucosal immunity and is primarily located in secretions such as saliva, tears, breast milk, and mucous membranes. This helps protect the body from pathogens entering through mucosal surfaces.

IgA exists in two forms: a monomeric form found in serum and a dimeric form, which is secreted at mucosal surfaces. The dimeric form, known as secretory IgA, is especially effective in preventing the attachment and invasion of pathogens in areas such as the gastrointestinal tract, respiratory tract, and urogenital tract.

While other immunoglobulins like IgE, IgD, and IgG have important roles in immune responses, they do not dominate in secretions to the same extent as IgA does, which defines its critical role in maintaining local immunity at mucosal surfaces.