IL21 and systemic lupus erythematosus: We therefore purified T-betlo BN cells (see Figure 8—figure supplement 1 for purification strategy) from the peripheral blood of SLE patients and stimulated the cells with the complete cytokine cocktail (IFNγ, IL-2, IL-21 and BAFF) plus R848 for 6 days in the continuous presence of anti-Ig (+,+), in the complete absence of anti-Ig (-,-) or in the presence of anti-Ig for the first 3 days (+,-) (Figure 8a).