FUNCTIONAL ACTIVATION OF ENCEPHALITOGENIC T-CELLS IN THE ABSENCE OF ANTIGEN-PRESENTING CELLS

Go-stimulatory signals provided by surface receptors of antigen-presen ting cells (APC) are crucial for the activation of CD4(+) T cells, cla ssically measured by cell proliferation or IL-2 secretion. The contrib ution of APC co-stimulatory signals to the acquisition of various effe ctor functions by activated T cells is not fully understood. We have n ow examined the importance of surface-mediated co-stimulation by APC f or activation of the effector potential of T cell clones mediating exp erimental allergic encephalomyelitis (EAE). We now report that T cell clones can be activated to produce EAE not only with APG but also by a ntibody-mediated TCR cross-linking in the presence of a mixture of T c ell growth factors. Without activation, the T cell clones did not caus e EAE. Therefore, at least some types of T cells can be activated to e xpress their effector potential in the absence of any surface co-stimu latory signals requiring intact APC.