Rheumatoid factors in mice: non-specific activators of heterophile rheumatoid factor production.

Although possibly the best, LPS is by no means the only non-specific activator of immune responsiveness (AIr). Plant lectins such as PHA and PWM have some ability to stimulate both total IgM production (reverse IgM PFC) and more particularly heterophile and homophile IgM rheumatoid factor (RF) responses, together with IgM 'antibody' responses to target antigens such as xenogeneic red blood cells or haptens such as TNP. Some parasitic infections and/or parasite antigens were shown to be powerful non-specific AIr, while the injection of dextran sulphate was shown to lead to a great increase in spleen cellularity and total IgM (reverse) PFC but failed to stimulate a heterophile (BIG) RF PFC response.