Induction of lymph follicle formation with endotoxin lipopolysaccharide in the draining lymph node of athymic nude mice.

Formation of lymph follicles in draining popliteal lymph nodes in athymic nude mice and their phenotypically normal littermates (PN mice) was investigated after footpad injection with either endotoxin lipopolysaccharide (LPS) or phytohemagglutinin in soluble and precipitated forms (PHA). The dose of LPS injected ranged from 10 to 100 micrograms, and that of PHA was 50 micrograms. After any dose of LPS, draining nodes of nude mice produced new lymph follicles in the peripheral cortex outside pre-existing follicles, though the number of follicles induced was somewhat less than in the case of PN mice treated with LPS. After injection of PHA in soluble or precipitated form, PN mice developed a significant number of new follicles in the draining nodes, but nude mice failed to do so. The present results are consistent with the view that nude mice have the ability to develop lymph follicles by way of a thymus-independent mechanism in response to exogenous stimuli.