Heavy chains

The heavy chains of Antibodies contain both the CDRH3 loop mediating a disproportionate number of contacts with antigens, as well as larger constant regions. They are also similar to Nanobodies (albeit larger).

Diversity

Heavy chains differ across different types of antibodies:

• IgA antibodies: $\alpha$-type heavy chain with three immunoglobulin domains
  • IgA1: $\alpha 1$
  • IgA2: $\alpha 2$
• IgD antibodies: $\delta$-type heavy chain with three immunoglobulin domains
• IgE antibodies: $ϵ$-type heavy chain with four immunoglobulin domains
• IgG antibodies: $\gamma$-type heavy chain with three immunoglobulin domains
  • IgG1: $\gamma 1$
  • IgG2: $\gamma 2$
  • IgG3: $\gamma 3$
  • IgG4: $\gamma 4$
• IgM antibodies: $\mu$-type heavy chain with four immunoglobulin domains