Functional tolerance induction in intact DO11.10 severe combined immunodeficiency (SCID) mice. Ovalbumin (OVA)-specific (CD4+ KJ1.26+) cells from naïve (a–c), OVA-fed (d–f) or OVA-immunized (g–i) DO11.10 SCID mice were analysed by flow cytometry for the expression of the indicated molecules. Plots shown are gated on CD4+ KJ1.26+ (a, d, g) or CD4+ (b, c, e, f, h, i) lymphocytes. (j) OVA-specific cells isolated from OVA-fed (tolerized) or OVA-immunized (primed) DO11.10 SCID mice were transferred into naïve BALB/c recipients prior to immunization with OVA/complete Freund’s adjuvant (CFA) (filled bars) or CFA alone (empty bars). Apoptosis of OVA-specific cells was assessed 20 hr later by measuring Annexin-V binding. (k) Naïve, tolerized or primed OVA-specific T cells were transferred into BALB/c recipients prior to immunization with OVA/CFA. Twenty hours later, draining lymph nodes (LNs) were isolated and cells cultured alone (empty bars) or re-stimulated with 5 μm OVA323–339 (filled bars). Supernatants were analysed for interleukin (IL)-2 after 24 hr of stimulation. CTLA-4, cytotoxic T-lymphocyte antigen 4; PD-1, programmed death-1.