53
however, not been studied. The data presented here suggest that the
altered cellular-state (an increase in blast-like cells concommitant
with an increase in TCA precipitable counts of unstimulated cultures)
in bluegill maintained for long laboratory periods are caused by envi
ronmental factors in the laboratory aquaria. A likely factor (admit
tedly speculative) might involve endotoxemia resulting from bacterial
infections acquired in the aquarium.
Evidence for Two Subpopulations of Lymphocytes
The studies reported here show that there are at least two sub
populations of lymphocytes in the bluegill. One population is stimu
lated by PHA and Con A at 32C and very poorly at 22C. Although not
proven directly, the cells responding in mixed lymphocyte cultures are
probably a subset of the PHA/Con A responsive population since MLC's
were obtained only at 32C. The other population of lymphocytes is
LPS-responsive at both 32C and 22C although responsiveness at 22C
was usually greater.
The two subpopulatins were shown to be different by anti-brain
\
serum cytotoxicity and rosette depletion experiments. The 32C, PHA
responsive population was depleted from the total population by anti
brain plus complement treatment and left intact by depletion of rabbit
RBC rosetted lymphocytes. The converse was true for the LPS-responsive
population. LPS-responsiveness was depleted by removal of rosetted
lymphocytes from the total population and was unaffected by anti-brain
cytotoxicity treatments.
Comparison of Bluegill and Rainbow Trout Mitogenic Studies
Differences between the results of mitogenic studies presented
here with the bluegill and those of Etlinger et al. (46) with rainbow