Secretion of IL-4 by OVA-Tg cells in primary in vitro cultures depends on the presence of CD4⁺ cells from TLI-preconditioned mice.

Highly purified naive OVA-Tg cells were cultured as in Figure 6 with OVA peptide and APCs from untreated BALB/c mice (▴), whole spleen from TLI-preconditioned BALB/c mice (●), or CD4⁺-depleted spleen from TLI-preconditioned BALB/c mice (▪) in IL-4 (upper) and IL-2 (lower) ELISPOT plates. Cytokine-producing cells were detected as described in “Materials and methods.” The data represent a single experiment. The experiment depicted in the upper panel was repeated twice with similar results.