In certain classes of antibody, the monomeric versions join to form dimers. what portions of the molecules adhere to each other to form these dimers?

There are five classes of antibody.

1) IgA (immunoglobin A)

2) IgD (immunoglobin D)

3) IgE (immunoglobin E)

4) IgG (immunoglobin G)

5) IgM (immunoglobin M)

They form Y shaped antibodies. The crystallized fragment is the stalk of the Y shaped antibodies. The bond formed by this stalk will determine the form of the antibody. One Y is called monomer, two connected Ys are called dimers, and 5 connected Ys are called pentamers.