On Assessing Immunocompetence

IVIG also does not contain IgA, IgE, IgM, or isohemagglutinins. [...]the presence of IgA and isohemagglutinins would indicate that the patient's B cells can isotype switch and make specific antibodies. [...]the T cells that are present can be shown to have normal function by testing their ability to proliferate in response to T-cell mitogens or to antigens. [...]these functional assays are of crucial importance in determining immunocompetence and in directing appropriate therapy.