Preferential induction of CD8⁺ T-cell responses by SL-encapsulated antigen in vivo.

Two mice were injected subcutaneously in the hindfoot pads with OVA-SL, OVA in positively charged liposomes (OVA-Cat), OVA in nonstabilized (conventional) liposomes (OVA-Conv), OVA as soluble protein (sOVA), OVA as soluble protein mixed with empty SL (based on the lipid concentration of OVA-SL) (sOVA + SL), or empty SL (SL). All animals immunized with OVA received a total of 8 μg OVA, and the amount of empty SL injected was based on the lipid concentration of OVA-SL. All animals were boosted on day 5 with the same antigen preparation received initially, and 5 days later draining LN were removed. The LN cell suspensions of the 2 animals from each group were pooled, and the CD8⁺ T cells were purified magnetically. Then 2.5 × 10⁵ CD8⁺ T cells were incubated with 3 × 10⁴ or 1.5 × 10⁴ BmDC, respectively, that had been incubated with OVA-SL (10 μg/mL) for 12 hours. T-cell proliferation was measured after 4 days, and mean cpm × 10⁻³ from a representative experiment is shown.