This study has defined the effects of cell concentration, culture cond
itions and mitogen concentration on the uptake of H-3-labelled thymidi
ne by mononuclear cells (SMC) purified from the spleens of ducks. The
mitogen stimulation of cultures containing from 5 x 10(2) to 2 x 10(6)
cells per well indicated that the optimal concentration of duck SMC w
as 5 x 10(5) cells per well. Cultures with concentrations of 1 x 10(6)
cells per well or more took up H-3-thymidine without the need for mit
ogenic stimulation. The response to each mitogen tested - phytohaemagg
lutinin (PHA), concanavalin A (ConA) and lipopolysaccharide (LPS) - wa
s distinctive, with between duck variation in the time for peak stimul
ation, the level of stimulation and the mitogen concentration required
for maximum stimulation. The response of the SMC of all the ducks was
strongest to stimulation with PHA, the response to ConA was variable
and the response to LPS was poor. Supplementation of the media with 20
per cent fetal calf serum instead of autologous duck serum was satisf
actory.