CD28 and rheumatoid arthritis: Side-by-side comparison of cell cultures of these RA patients (RA #7, 8, 9) demonstrated significant (p = 0.0389) but moderate activity of SF cells in inhibiting the robust proliferation of anti-CD3/CD28-stimulated autologous T cells (Figure 3A), and also significant (p = 0.0087) and more effective suppression of the Ag-induced (and more modest) proliferation of the same T cells (Figure 3B).