Induction of lymph follicle formation with several mitogens and adjuvants in the mouse popliteal lymph node

The formation of lymph follicles in draining popliteal nodes was investigated in young adult male mice which had been injected in the rear footpad with several mitogens and adjuvants, and killed after 3-21 days. PPD (100 micrograms-1 mg) and PHA (25-500 micrograms) induced germinal centers in association with existing follicles and mild plasmacytosis, but failed to produce new follicles in draining nodes. Endotoxin LPS (50-200 micrograms), Con A (50 micrograms-1 mg) and PWM (50 micrograms-1 mg) induced germinal centers within existing follicles and plasmacytosis, and also produced new follicles which soon developed germinal centers. Both Freund's complete and incomplete adjuvants (FCA and FICA, 25 microliters) induced virtually no germinal centers and plasmacytosis, but produced a significant number of new primary follicles. Poly (A, U) (600 micrograms) produced neither germinal centers nor plasmacytosis, and did not induce new follicles. Analysis of the distribution of lymphoid cells which had incorporated 3H-thymidine in the draining nodes at 3 days after the injection of test substances indicated that PPD, PHA, LPS, Con A and PWM preferentially stimulated in vivo the same types of lymphocytes as they do in vitro. FCA triggered lymphocyte activation in the deep cortex, whereas Poly (A, U) appeared not to stimulate lymphocytes in vivo. In further experiments, induction of lymph follicles with artificially precipitated PPD and PHA was studied. The draining nodes treated with alum-precipitated PPD or PHA were found to produce a significant number of new follicles.(ABSTRACT TRUNCATED AT 250 WORDS)