Question

lgA ______.

Options

• is present in milk and saliva

• is involved in hay fever

• activates complement by the classical pathway

• crosses the placenta

Answer 1

lgA is present in milk and saliva.

Explanation:

IgA is a type of immunoglobulin primarily found in body secretions like milk, saliva, tears, and mucosal linings. It plays an important role in mucosal immunity by preventing pathogens from adhering to and invading epithelial cells. IgA is not involved in hay fever (which involves IgE), does not activate complement via the classical pathway (that is IgG and IgM), and does not cross the placenta (this is a feature of IgG).