115
quantitated by indirect immunofluorescence. The results are presented
in Table 24. Very few positive cells were seen in cell preparations
(Hypaque-Ficoll isolates) before culturing. There was an increase in
the number of immunoglobulin containing cells in PHA-stimulated cultures
as compared to cells which were not cultured. However a similar in
crease was also seen in unstimulated cultured controls as well, and was
considered to be a nonspecific increase due to culture conditions. On
the other hand LPS-stimulated cultures showed a significant ( p < 0.01)
increase in the number of immunoglobulin positive cells over uncultured
control, cultured control and PHA-stimulated cultures indicating that
LPS stimulates immunoglobulin production in alligator lymphocytes as
it does in mouse lymphocytes.
In Vitro Studies on Antibody Producing Cells
Due to the limited number of alligators available and the necessity
of maintaining "normal" alligators as blood donors for in vitro experi
ments, it was not possible to study rn vivo immune responses. However,
one preliminary experiment was performed to determine if peripheral
white blood cells isolated from Hypaque-Ficoll were immunocompetent in
a primary in vitro immunization assay (Mishell-Dutton type cultures).
Control (without SRBC) or immunized (with SRBC) cultures were maintained
at 32C and assayed for the number of cells producing antibody to SRBC's
after various periods of incubation. The results are presented in Table
25. Only cells from immunized cultures contained plaque-forming cells.
The peak response occured after seven days of culture (two days later
than the optimal time for mitogenic stimulation). It should be pointed
out that a decrease in the number of plaque-forming cells on day 10 may