Age-dependent isotype variation during secondary immune response in MRL/lpr mice producing autoanti-gamma-globulin antibodies.

A profound inability to produce IgG anti-2,4,6-trinitrophenyl (TNP) antibodies during the secondary immune response elicited by a T-dependent antigen was observed in aged MLR/lpr mice. This unresponsiveness is associated with a significantly low indirect anti-TNP plaque-forming cell response and a weak in vitro anti-TNP response upon the culture of keyhole limpet hemocyanin-primed T cells and TNP-primed B cells in the presence of TNP. The markedly low IgG anti-TNP response observed in aged MLR/lpr mice cannot be related to the presence of rheumatoid factors which are observed during the secondary response, since MRL +/+ and 129/J mice, (non-autoimmune disease strains), also produce significant amounts of anti-gamma-globulin antibodies yet mount a strong IgG anti-TNP response.