Ig vs human gamma globulin

Ig and human gamma globulin both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ig	Yes	No	No	No
human gamma globulin	Yes	No	No	No

As nouns, human gamma globulin is a hypernym of Ig; that is, human gamma globulin is a word with a broader meaning than Ig:

Ig: a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response
human gamma globulin: a plasma protein containing the immunoglobulins that are responsible for immune responses

Other hypernyms of Ig include gamma globulin, antibody.

Ig (noun)	human gamma globulin (noun)
a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response	a plasma protein containing the immunoglobulins that are responsible for immune responses