Anti-horse globulin antibodies in human sera.

Organ transplant patients who had received ALG, patients with rheumatoid arthritis and normal persons were studied for serum antibodies to horse globulins. Although normal individuals rarely show the presence of anti-horse antibody, rheumatoid patients with high titres of rheumatoid factor usually show anti-horse globulin agglutinins in their IgM globulins and these agglutinins are considered to be a manifestation of their `rheumatoid factors'. These agglutinins are readily absorbable with aggregated human γ-globulin. On the other hand, although most transplant patients administered ALG produce anti-horse antibody, it is usually produced as an IgG globulin and it is not absorbable with aggregated human γ-globulin.