99
clearly indicated that there were at least two different effects on the
stimulation of lymphocytes by the different combinations of mitogens.
The effect of LPS + PHA was synergistic since the response was ^2.5
times higher (p < 0.01) than the PHA response alone, 'v 20 times (p <
0.001) higher than the LPS response and greater than a twofold increase
of the sum of the LPS and PHA responses. The effect of PWM + PHA or PWM
+ Con A was antagonistic, in that the responses were 'v 0.6-0.7 times
lower (p < o.o5) than the PHA or Con A responses. The results from LPS
+ PWM, PHA + Con A and LPS + Con A stimulations were not sufficiently
conclusive to determine if the effects were additive or synergistic.
Effect of Environmental Temperature on LPS Responsiveness
During the winter months a decrease in LPS responsiveness of alli
gator peripheral blood lymphocytes was observed. A subsequent return
of responsiveness to LPS occurred with the arrival of spring weather.
The data compiled from studies of one alligator from Nov. 20, 1975,to
Feb. 27, 1976,are presented in Figure 15. Since the animals were housed
outdoors and the winter was unusually cold, it was hypothesized that
such colder environmental temperatures may have effected the circulating
population of LPS-responsive lymphocytes. To test this hypothesis two
alligators were housed indoors at 16C for an extended period of time
and the mitogen responsiveness of their peripheral blood lymphocytes
(cultured at 32C) was monitored periodically. The results presented
in Table 20 indicate that environmental temperature did significantly
effect the LPS-responsive population since a LPS response was not de
tected in either alligator after 36 days at 16C. Although the PHA
response appeared to drop also it was nonetheless present when the