Table 1.—Serum hemagglutination titers of fish immunized by intraperitoneal injection of sheep red 
blood cells (SRBC) at the time of 96-hr cadmium exposure. Sera were drawn 2 wk later (1 wk after a 
second SRBC injection). 
Cadmium concentration (ppm) 
0 3-6 12-24 
No. No. No. 
tested Titer? tested Titer tested Titer 
Immunized fish 12 338411 95} 29+6 17 30+5 
Nonimmunized fish 9 6+1 12 3841 12 6+1 
' Titer is shown as the reciprocal of the mean serum dilution+standard error. 
treatment, no differences were noted in eventual 
amount of antibody produced; therefore, the data 
in the table are grouped as though all antigen injec- 
tions were given on the same day. 
It may be seen from the table that treatment of fish 
with low doses (3-6 ppm) or high doses (12-24 ppm) of 
Cd?* did not cause any significant differences in an- 
tibody response over those produced by fish not ex- 
posed to Cd**. The table also shows that fish had a 
natural, low-level agglutinin to SRBC which was dis- 
tinguishable from immune agglutination by its lower 
titer. About half of the fish tested had no natural 
SRBC agglutinins. All fish treated with 48 ppm cad- 
mium died within the 2-wk holding period even 
though held in fresh, Cd*+free water. 
Effects of Cadmium on Bacterial Clearance 
Experiments were run to determine whether 
cadmium exposure would affect another aspect of im- 
munity in cunners, namely, clearance of bacteria by 
phagocytic cells of the reticuloendothelial system. 
The two primary elements of this system, the liver 
and spleen, were examined. Bacteria injected into the 
bloodstream via intracardial route were counted after 
30 and 90 min for their remaining levels in the blood, 
for quantities picked up in the liver and spleen, and 
(by subtraction) for quantities killed within the 30- 
and 90-min time intervals. Five experiments were run 
in which a total of 10 or 11 fish were used for each of 
the following four variables: 0 ppm Cd’+ at 30 min, 
12 ppm Cd’* at 30 min, 0 ppm Cd?+ at 90 min, and 
12 ppm Cd**+ at 90 min. Fish caught and used in 
the warm summer months had significantly greater 
clearance rates than those caught and used in the 
autumn; however, the relationships of the 30- and 90- 
min effects and the 0 ppm and 12 ppm Cd?**+ effects 
were approximately the same. Therefore, to get a 
representative mean (one in which the low count ex- 
periments would carry as much weight as high count 
experiments), each value within an experiment was 
multiplied by a factor for that experiment according 
to the following example: 
mean of all values 
Factor, = 
mean for experiment #1 
This allowed each experiment to be representative in 
calculating the mean while preserving all the treat- 
ment effect relationships within that experiment. 
Figure 1 depicts the effects of Cd** on clearance of 
bacteria. Wilcoxon’s signed rank test for paired obser- 
vations was used to determine significance of effects 
O ppm CADMIUM 12 ppm CADMIUM 
Significant 
Differences: 
z B (.02<P<.05) 
= L(P.05) 
fo) 
o 
Aes Blood (B) & 
= 3/69 Spleen(S) Ef 
o Ol/yo Liver (L)&Q 
oOo Clg — 
=i Rl 
BE|o 3 
oo\na 
Significant 
Differences: 
yA B+L+S (P01) 
fo) 
Oo 
60 MIN. 
Figure 1.—Bacterial clearance from the blood, liver, and 
spleen. Diagrams represent mean percent of bacteria remain- 
ing (based on number of bacteria injected) after the 30- or 90- 
min time intervals. Values from 10 or 11 fish were used for each 
variable. 
