LPS augments adoptive transfer of experimental allergic encephalomyelitis in the Lewis rat

Adoptive transfer of experimental allergic encephalomyelitis (EAE) is enhanced after in vitro culture of myelin basic protein (BP)-sensitized lymphoid cells with BP. Addition of lipopolysaccharide (LPS) to the culture further augments transfer of EAE to a level 5 times greater than that achieved with cells activated only with BP. Neither the proliferative response of a BP-specific cell line nor the production of IL-2 by BP-sensitized lymphoid cells in response to BP was augmented by the addition of LPS to the culture. Augmentation of EAE was also observed if recipients received simultaneous injections of BP-sensitized lymph node cells (BP/LNC) cultured with BP (BP-activated) and normal spleen cells cultured independently with LPS (LPS/Spl-C). To analyze the effect of contact between these two cell populations in vivo, we mixed the two cell populations in vitro at reduced cell concentrations. When BP-activated BP-LNC were mixed with LPS-Spl-C in vitro, a marked synergistic proliferative response was observed. Irradiation of BP-activated BP/LNC abrogated this synergistic response, whereas irradiation of LPS/Spl-C did not, suggesting that the proliferating population was in the BP/LNC and that the LPS/Spl-C enhanced their proliferation. These results indicate that LPS exerts its effect through BP-nonspecific cells and that these cells enhance transfer of EAE by augmenting the proliferation of the BP-specific cells in vivo after transfer.