Lewis rat lymphoid dendritic cells can efficiently present homologous myelin basic protein to encephalitogenic...

Lymphocytes isolated from Lewis rats immunised with protein antigen in adjuvant were stimulated to proliferate in vitro by splenic dendritic cells (DC) which had been pulsed with purified homologous myelin basic protein (MBP). By contrast, in parallel experiments, lymphocytes did not respond to ovalbumin unless the protein was first processed by macrophages by a chloroquine-sensitive mechanism. DC, pulsed with rat MBP at concentrations as low as 6 micrograms/ml, activated lymphocytes for transfer of severe experimental autoimmune encephalomyelitis (EAE). MBP dissociating from myelin membranes in physiological medium, as well as MBP purified from highly acidic extracts of myelin, was effective for pulsing DC; preincubating myelin with macrophages led to a reduction rather than an enhancement in the severity of the EAE transferred. It is concluded that macrophage-mediated antigen processing is not required for immunogenic presentation of the determinants of MBP which cause EAE in Lewis rats. Furthermore, MBP-pulsed DC may prove useful in experiments requiring activation of encephalitogenic T cells.