“…subacute bacterial endocarditis [20], infectious mononucleosis [8], trypanosomiasis [21], pulmonary disease [22], in human allograft recipients [23] and in occasional healthy invididuals [24,25]. The antiglobulins present in the sera of patients with rheumatoid arthritis, i.e., rheumatoid factors, are specific mainly for determinants on the Fc portion of both rabbit and human y G [6]; by contrast, the anti globulins found in non-rheumatoid diseases and in occasional healthy subjects aie usually reactive only with human y G [18,22,26]. Moreover, hidden rheumatoid factors have been described recently in the sera of certain rheumatoid subjects [27,28].…”