<prompt> Which of the following immunoglobulin does not fix complementIgAIgGIgMIgE  <response>: Ref Robbins immuno system chapter ... immunoglobulin topic ; see tables for details complement-fixing antibody antibody primarily IgM and the IgG subclasses 1, 2, and 3 that activates complement when reacted with antigen. ... In humans this antibody, also known as reagin, is of the immunoglobulin class known as IgE. 