Figure 6.

ICAM-1 expression by splenic APC down-regulates IL-4 production. (A) D011 CD4⁺ T cells were cultured with limiting numbers of T-S alone (2.5 × 10⁵), with Drosophila APC expressing class II H2-A^d plus B7–1 (1.25 × 10⁵), or with a mixture of T-S (2.5 × 10⁵) and Drosophila APC (1.25 × 10⁵). IL-2 and IL-4 production was measured on day 4. (B) CD4⁺ T cells purified as in Fig. 1 from normal D011 mice were cultured with Ova peptide and T-S from normal mice or ICAM-1-deficient mice. The indicated cytokines were measured on supernatants taken at various times after culture with 0.01–10 μM Ova; peak responses at day 3 with 10 μM Ova are shown. The peak proliferative response to Ova was equivalent with normal and ICAM-1-deficient APC, though responses with ICAM-1 deficient APC required higher concentrations of peptide. (C) Nylon wool purified D011 lymph node cells were FACS sorted for CD4 expression and high expression of CD62L. These naive phenotype cells were cultured with a titration of Ova peptide and with splenic APC (either from normal or ICAM-1-deficient mice) or with Drosophila APC expressing the indicated accessory molecules. Cytokines were measured on days 1–4 and the peak responses are shown: for IL-2, day 3, for IL-4 and IFN-γ, day 4.