The immunomodulatory effect of human IgG Fc fragments on the oxazolone-specific immune response of high and low responder mice.

Intravenous injection of human IgG Fc fragments in mice resulted in the stimulation or inhibition of an oxazolone-specific antibody response depending on the schedule of Fc fragment injection. High and low responder mice for oxazolone were injected with Fc fragments according to two protocols: either on the day of oxazolone priming, or together with the oxazolone boost, and the isotype composition of oxazolone-specific antibodies was analysed by solid phase radioimmunoassay. We found the primary and secondary anti-oxazolone IgM levels increased in all instances, irrespective of the schedule of Fc fragment treatment. In contrast, the oxazolone-specific IgG production was increased only if Fc fragments were injected at the time of antigen priming. Injection of Fc fragments together with a secondary injection of oxazolone resulted in the inhibition of oxazolone-specific IgG production. Both stimulation and inhibition of oxazolone-specific antibodies were more pronounced in the low responder C57BL/6 mice strain.