Immunoglobulin names are abbreviated as Ig, followed by a letter to show the class and an arabic numeral for subclass:
IgA IgE IgG IgM IgG1 IgA2
A number of immunoglobulin fractions are prepared from human plasma and used for treatment of a variety of human conditions. Use lower case for the names, and abbreviate using initial capitals followed by Ig (no space):
intravenous immunoglobulin (IVIg)
subcutaneous immunoglobulin (SCIg)
normal human immunoglobulin (NHIg)