Figure 3.

Serum procalcitonin (PCT) and calcitonin (CT) immunoreactivity in WT and Calca KO mice. (A) Combined levels of serum PCT and CT were measured in WT and KO mice (five per group) using a two-site immunoradiometric assay for rat CT, both under baseline (Bsln) conditions and 24 hours after challenge with 5.0 × 10¹⁰ CFU/ml of aerosolized S. pneumoniae (S.p.) that kills 20–80% of infected mice after 3 days. *P < 0.001 compared with unchallenged WT mice. (B) Combined levels of serum PCT and CT were measured in WT and Calca KO mice (five per group) using a standard radioimmunoassay for human CT under baseline control conditions, 24 hours after challenge with 5.0 × 10¹⁰ CFU/ml of aerosolized S. pneumoniae, or 2 hours after intraperitoneal challenge with human parathyroid hormone (0.5 μg/g body weight) to elevate serum calcium levels. *P < 0.001 compared with unchallenged WT mice.