<prompt> The following constitutes approximately 75 of total immunoglobin in humans -IgGIgMIgEIgA  <response>: IgG is the main serum immunoglobulin consisting of 80 of the total. equally distributed between intravascular and extravascular compaments. The normal serum concentration of IgG is about 8-16 mg per ml. Reference : Anathanarayan panikers 9th edition, pg no: 96, p 