Bound immunoglobulin and complement in heart allografts undergoing rejection

A series of dog heart allografts and one human heart transplant undergoing rejection were examined by immunofluorescence for bound immunoglobulin. Deposits of y-globulin were seen in a few scattered myocardial fibers in canine heart allografts 2 or 3 days after grafting, progressing to widespread, intense staining in hearts examined by the 5th and 7th days. A human heart rejected on the 5th day showed extensive deposits of IgG in the myocardium, as well as complement components Clq and C3 and fibrin, in the same location. Both in the human and in some of the later dog heart transplants, large mononuclear cells containing y-globulin were seen infiltrating the myocardium. Serum from six human heart transplant recipients was examined for presence of antibodies. Two of these recipients had alloantibodies reacting with an established human tissue culture cell line and four demonstrated autoantibodies to human heart. Immunoglobulin deposits in rejecting heart allografts, here described, could also represent either alloantibodies or autoantibodies, or both. Their role in rejection remains speculative