The phrase "heavy chain" refers to a large and strong type of protein in our bodies. These proteins play important roles in various functions, such as supporting our immune system and helping our muscles work. Full definition
This bag is one I have had my eye on for some time, grey velvet with heavy chains, it goes with anything and everything, a superb size too. (lazydaisyjones.com)
Weight: How heavy your chain will weigh on your neck is an important factor when considering how to best choose a chain you can wear comfortably. (geekwrapped.com)
A third section links the two heavy chains together to form the stem of the «Y». (immunology.org)