Many human RF-associated crossreactive idiotypes (CRIs) have been defined. Since these
CRIs probably are the phenotypic markers of Ig variable region genes, the data suggest that
human RFs employ several Ig variable region genes which are common among outbred
human populations. There are at least four types of stimuli which can trigger RF production.
They are aggregated IgG in the form of antigen-antibody complexes, exogenous antigens
bearing cross-reactive determinants to human IgG, autologous antibodies which mimic the …