Immunologic responses of mice to lipopolysaccharide from Escherichia coli.

Abstract

The immune response of athymic and normal mice to lipopolysaccharide (LPS) from Escherichia coli 0113 was studied. Normal mice could be primed by subnanogram amounts of LPS for a secondary response to a dose of the same LPS; the magnitude of the antibody response was proportional to the size of the primary dose, as was the specific plaque-forming cell (PFC) response to a similar regimen of LPS. The amount of LPS required for priming was 106-fold less than that required to initiate a primary PFC response. The thymus-independent nature of the immune response of mice to LPS was confirmed and expanded. Congenitally athymic (nude) mice responded in both primary and secondary fashions to LPS in a manner similar to normal littermates that had intact thymuses. This phenomenon could be demonstrated at various dosage levels. Furthermore, the response to LPS in nude mice was demonstrable concomitantly with the demonstration of a severely impaired response to equine erythrocytes; the latter response is thymus-dependent.