Development of lymphocyte blastogenic response in the neonatal period of foals

The blastogenic response of lymphocytes and serum concentration of cortisol from eighteen foals were evaluated during various stages of the neonatal period. The results of blastogenic responses were expressed by a stimulation index (SI). Blastogenic response to three mitogens was lowest at birth (PHA: 1.17 +/- 0.02, Con A: 1.11 +/- 0.05 and PWM: 1.02 +/- 0.01), then increased gradually with slight variations postpartum. The serum concentration of cortisol was highest at birth (44.0 ng/ml) and decreased rapidly to 19.3 ng/ml within 1 week postpartum, and then was maintained at this level. The high serum concentration of cortisol at birth may be associated with decreased blastogenic response of lymphocytes in foals.