IgG4: a possible mediator of anaphylaxis in a haemophiliac patient.

Immunological investigations have been carried out on a haemophiliac patient who had developed severe anaphylaxis to bovine factor VII administration. Results have shown that the development of anaphylaxis in this patient was associated with a sudden increase in total and specific IgG4 antibodies. The significance of this observation is discussed in relation to current evidence suggesting the involvement of IgG4 antibodies in some anaphylactic conditions.