FIGURE 6.

The ability of PMNs to kill intracellular bacteria declines with age and is controlled by A1 receptor signaling. (a) PMNs were isolated from the bone marrow of young and old male C57BL/6 mice. (b) PMNs isolated from the bone marrow of young mice were treated with either the A1 receptor inhibitor 8‐cyclopentyl‐1‐3‐dipropylxanthine (3.9 nM) or PBS as vehicle control (VC) for 30 min at 37°C. (c) PMNs isolated from the bone marrow of old mice were treated with either the A1 receptor agonist 2‐chloro‐N6‐cyclopentyl adenosine (0.8 nM) or PBS as vehicle control (VC) for 30 min at 37°C. (a–c) PMNs were then infected with pre‐opsonized S. pneumoniae for 15 min at 37°C. Gentamicin (100 μg/ml) was then added for 30 min to kill extracellular bacteria. PMNs were washed and plated on blood agar plates to determine the % of viable bacteria of the original infecting inoculum. The fold difference in viable intracellular bacteria was then calculated by dividing the values of (a) old reactions by young controls, (b) A1 receptor inhibitor treated reactions by vehicle treated controls, and (c) A1 receptor agonist treated reactions by vehicle treated controls. *Significantly different from 1 by one‐sample t‐test