Innate immunity is non-specific type of defence, that is present at the time of birth. This is accomplished by providing different types of barriers to the entry of the foreign agents into our body.Acquired immunity, on the other hand, is pathogen specific. It is characterised by memory. This means that our body when it encounters a pathogen for the first time produces a response called primary response.When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity. Different types of antibodies are produced in our body. IgA, IgM, IgE, IgG are some of them.

Which immunoglobulin is largest?

IgM

The structure of IgM is predominantly hexameric, This makes IgM most largest.