Fine Specificity and Isotype Expression of Anti-PC Antibodies in BALB/c, MRL/Mp-1pr/1pr, and -+/+ Mice at Different Ages

Abstract

The MRL/Mp congenic mouse strains develop autoimmune disease with age. We have investigated age- and autoimmune-related changes in fine specificity, isotype spectra and T15 idiotype expression of the anti-phosphorylcholine (PC) response in BALB/c, MRL/Mp −+ and -lpr congenic mice and in (BALB/c x MRL/Mp-lpr) F1 hybrids. Two groups of anti-PC antibodies with distinct fine specificity are elicited in the memory response. Group I antibodies recognize the PC moiety and express the T15 idiotype. Antibodies of group II are specific for phenyl-phosphorylcholine and are found predominantly in the memory response. In the MRL/Mp-lpr and −+ strains only a minor population of antibodies expresses the T15 idiotype at all ages. However, a third group of antibodies was observed which binds to PC-coated proteins and to Diplococcus pneumoniae R-36A. This binding was not inibited by PC-chloride and appeared mainly in the memory response at old age. The isotype distribution among anti-PC antibodies was similar in all strains analysed. In the initial response primarily μ, γ3 and γ1 isotypes were produced, while in the memory response γ1 was dominant. Thus autoimmune defects and ageing result in altered anti-PC antibody and idiotype profile, probably related to altered states in both the T- and B-cell compartments.