Using the parent-into-F1 model of induced lupus and (C57Bl/6xDBA2) F1 mice as hosts, we compared the inherent lupus-inducing properties of the two parental strain CD4 T cells. To control for donor CD4 recognition of alloantigen, we used H-2d identical DBA/2 and B10.D2 donor T cells. We demonstrate that these two normal, non-lupus prone parental strains exhibit two different T cell activation pathways in vivo. B10.D2 CD4 T cells induce a strong Th1/CMI pathway characterized by IL-2/IFN-g expression, help for CD8 CTL, skewing of DC subsets towards CD8a DC, coupled with reduced CD4Tfh cells and transient B cell help. By contrast, DBA/2 CD4 T cells exhibit a reciprocal, lupus-inducing pathway characterized by poor IL-2/IFN-g expression, poor help for CD8 CTL, skewing of DC subsets towards pDC coupled with greater CD4 Tfh cells, prolonged B cell activation, autoantibody formation, and lupus-like renal disease. Additionally, two distinct in vivo splenic gene expression signatures were induced. In vitro analysis of TCR signaling revealed defective DBA CD4 T cell induction of NF-κB, reduced degradation of IκBα and increased expression of the NF-κB regulator A20. Thus, attenuated NF-κB signaling may lead to diminished IL-2 production by DBA CD4 T cells. These results indicate that intrinsic differences in donor CD4 IL-2 production and subsequent immune skewing could contribute to lupus susceptibility in humans. Therapeutic efforts to skew immune function away from excessive help for B cells and towards help for CTL may be beneficial.