Figure 4.

Effects of age on tolerance to other TAChR α-chain epitopes. Young (5 months of age) and old (23-25 months of age) mice were immunized s.c. in multiple sites with the recombinant Talpha (aa 1-210) as described in Methods. The immunizations were repeated twice at monthly intervals. The tertiary immunization was given at staggered time points (experiments A, B, and C) and draining lymph nodes were harvested 7 days later. T cells were stimulated with incremental concentrations of Talpha (aa 1-210) or the TAChR peptide, p146-162 and [³H]-thymidine incorporation was measured. The responses to 19 nM Talpha (Panel A) or 19 nM p146-162 (Panel B) are shown graphically for individual mice. One old nontransgenic and two old transgenic mice had enlarged spleens (>7 mg/g body weight) but responded to positive controls and thus were included in the tolerance study. Two mice with insufficient draining lymph node cells or with T cells that were not responsive to the Mtb control were not included; these mice also had enlarged spleens. The upper 95% confidence limit for the mean of young transgenic responses (dashed line) and the mean values for each group (solid line) are indicated.