EFFECTS ON IMMUNE RESPONSE 105Figure 5.7. Effect of 15 rads upon response of A/J mice to varying numbers of
mitomycin-treated Sal cells. Groups of 20 mice were exposed to 15 rads
whole-body irradiation or sham-irradiated, and inoculated subcutaneously
with the indicated numbers of mitomycin-treated tumor cells. Twenty-one
days later, all animals received 104 untreated Sal cells and were followed for
tumor size. A control group (solid line) did not receive mitomycin-treated
cells. Adapted from Anderson et al.12
- The augmentation is much more pronounced and appears to be
unequivocal. - The doses associated with each phase are distinctly different.
The introduction of antigen, either in vivo or in vitro, results in the rapid
expansion of the corresponding subsets of lymphocytes. This entails the
rapid division of the involved cell types. Cell division may also be occa
sioned by the introduction of a group of related plant derivatives termed
mitogens.
In the context of radiation injury of the immune response, mitogens have
the added advantage of selectively stimulating specific subpopulations of
lymphocytes. Phytohemagglutinin (PHA), for example, stimulates both
helper and suppressor T cells, Concanavalin A (Con A) activates propor
tionately more suppressor cells, and lipopolysaccharide (LPS) activates B
cells. Figure 5.13 shows the effect of various doses of radiation on the in
vitro response of mouse spleen cells to the indicated mitogens.24 Augmented
responses are seen with both PHA and Con A.