In vitro proliferation of OVA-reactive T cells from immunized mice. BALB/c (○) and plt/plt (•) mice were immunized subcutaneously in the hind foot pads with OVA in CFA. Popliteal LN cells were harvested at indicated days or 16 months after immunization, stimulated in vitro with OVA for 4 days, and assessed for proliferation. Mean ± SD from triplicate tests is indicated.