Immune responses to polyethylene glycol modified L-asparaginase in mice

Suppression of anti-L-asparaginase (anti-A-ase) IgG and IgE antibody responses was achieved in Balb/c mice with polyethylene glycol (PEG, MW, 5,000) conjugated Escherichia coli A-ase. Following the administration of the mixture of A-ase and PEG-A-ase, antibody production to A-ase was reduced. PEG-A-ase administration prior to A-ase suppressed the primary and secondary responses to A-ase antibody. The suppression could be transferred to normal mice with spleen cells from A-ase tolerant mice. The cell transfer experiment showed that the suppression was caused by suppressor T cells. Since PEG-A-ase administration failed to suppress antibody response to ovalbumin, the suppression seemed to be A-ase specific. PEG-A-ase administration also suppressed the delayed type hypersensitivity reaction. IgG and IgE antibodies to PEG or PEG-A-ase were not detected in mice immunized with PEG or PEG-A-ase in the presence of Freund's complete adjuvant or A1(OH)3, respectively.