EFFECT OF AGE ON ANTIBODY-RESPONSES IN LOW RESPONDER C57BL 10SCSN ANDHIGH RESPONDER A/J STRAINS OF MICE/

The IgM antibody response to sheep red blood cells (SRBC) appeared sig nificantly earlier in A/J strain mice (already in 10-day-old animals), but after 21 days responses were higher in B10 mice. These difference s disappeared after reaching adulthood and IgM responses after either primary or secondary immunization were thereafter comparable in these strains. High-responder A/J mice made significantly more IgG antibodie s than low-responder B10 mice from 21 days of age and strong differenc es lasted until the age of 19 months, when IgG antibody production was again similar. Potentiation of IgM formation by simultaneous applicat ion of 10 mug of LPS was higher in B10 mice until 19 months of age. On the other hand, potentiation of the IgG response was markedly high in B10 mice only in adult animals (3 months). Thereafter the potentiatio n was higher in A/J mice. The onset of Ig secretion in A/J mice was at 15 days and markedly increased at the age of 30 days. Levels of immun oglobulin synthesis remained extremely low in B10 mice, Age-related ch anges in IgG antibody production generally correlated with the decline of MHC class II antigen expression on peritoneal macrophages in these strains.