Autoreactive T cells from MRL- lpr lpr mice secrete multiple lymphokines and induce the production of IgG anti-DNA antibodies

The study of T cells in individuals with systemic lupus erythematosus has been limited because a specific marker for the disease has not been identified. To approach this issue, we isolated autoreactive T cell clones from lupus-prone MRL mice, a strain that develops an accelerated form of lupus. These CD4⁺ T cell clones grew spontaneously from unimmunized mice, and were maintained in culture by intermittent stimulation with syngeneic antigen presenting cells in the absence of exogenous antigen. One autoreactive T cell clone, termed ARTC-1, previously reported to have atypical MHC requirements for activation (both I-A^k and I-E^k were required) and to stimulate B cell proliferation and Ig production in vitro, was found to have an unrestricted pattern of lymphokine secretion. Following stimulation, it produced IL-4, IFN-γ and IL-2. ARTC-1 induced B cell proliferation both by cell contact and through secretion of soluble lymphokines. B cell proliferation by cell-cell contact was MHC restricted in a manner analogous to ARTC-1 activation by APCs; the B cell response was inhibited by both anti-I-A^k and anti-I-E^k antibodies. The ARTC-1 B cell interaction was also found to result in the production of IgG autoantibodies. These observations suggest that cells such as ARTC-1, if unregulated, could lead to B cell stimulation and autoantibody production in vivo, in the absence of exogenous stimulation. Furthermore, IFN-γ production by ARTC-1 could also result in enhanced class II expression, leading both to additional T-B cell interactions and to T cell interactions with endogenous cells capable of expressing class II antigens in other organs.