96
for each mitogen, with the exception of the splenic lymphocyte response
to LPS, in which case no response was observed. PHA and Con A responses
in the two preparations were comparable. Responses to PWM and PPD were
similar (p > 0.1) for splenic and peripheral blood lymphocytes.
Mixed Lymphocytes Cultures
Peripheral blood lymphocytes from different alligators were test
ed for their ability to respond in two-way mixed lymphocyte cultures
(MLC's). Eight alligators were bled and the lymphocytes isolated by
Hypaque-Ficoll. The results of all possible two way MLC's as well as
PHA stimulation indices (from individual animals) are presented in
Table 18. Optimal MLC responses were obtained on day 5 and remained
high through day 7. There was a wide spectrum of responses, expressed
as stimulation index, ranging from 1 (no response) to 12.5. Although
the response to PHA was significantly lower (p < 0.05) in one of the
alligators (alligator number 4) than the other seven, there was no
correlation between a low response to PHA and the ability to respond in
MLC.
The Combined Mitogen Effects on Lymphocyte Stimulation
The responses of alligator peripheral blood lymphocytes to various
combinations of the mitogens w'ere assayed to determine if different com
binations would give additive, synergistic or antagonistic effects. The
data from one experiment are presented in Table 19. Although in some
cases it was difficult to determine if the combined effects were addi
tive, synergistic or antagonistic when compared to the results from
cultures stimulated with only one mitogen, the results from culturing
lymphocytes with combinations of LPS + PHA, PWM + PHA and PWM + Con A