Double immuno diffusion method

Question

What do you mean by the double immuno diffusion method?

Answer 1

In this approach, both the antigens and the antibodies diffuse radically from the wells towards each other by forming the concentration gradient. As equivalence is achieved, a visible line of the precipitation is observed.
The patterns of the precipitin lines which are formed when the two different antigens are situated in the adjacent wells indicate if they share any common epitope or not.

Recognition takes place when the two antigens share the same epitopes; therefore, the line of precipitation made by them will combine to provide single curve line of identity.
Non-identity occurs when the two antigens are unrelated. The antiserum form independent precipitin lines which cross each other.

Partial identity takes place when two antigens share the common epitope. The antiserum forms line of identity along with the common epitope and the curved spur with unique epitope.