Ig vs immunoglobulin

Ig and immunoglobulin both are nouns.

Word	Noun	Adjective	Verb	Adverb
Ig	Yes	No	No	No
immunoglobulin	Yes	No	No	No

As nouns, Ig and immunoglobulin are synonyms defined as:

Ig and immunoglobulin: a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response

Other synonyms of Ig include immune gamma globulin, immune globulin, immune serum globulin.

Ig (noun)	immunoglobulin (noun)
a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response	a class of proteins produced in lymph tissue in vertebrates and that function as antibodies in the immune response