Suppression of the PCA reaction correlate with fasting duration and serum D-BHB concentrations. Evans blue dye (EVD) leakage (A), Typical photographs of the PCA reaction (B), Bar: 10 mm Serum D-BHB concentration (C). Values are means ± SEM, n = 7-27 rats. *P < 0.05 significantly different from ad libitium (AL). Correlation between EVD leakage and D-BHB concentrations (D). n = 87 rats. Fasting duration was determined as the time between food removal and antigen challenge.