Figure 3

Sera from RA patients inhibit T cell-induced TNF-α production by monocytes from healthy donors. (a) Peripheral-blood T cells (10⁶/ml) were cultured for 48 hours in the presence of immobilized anti-CD3 (3.3 μg/ml) and soluble anti-CD28 (0.8 μg/ml) antibodies. The cells were fixed and incubated for 24 hours with freshly isolated monocytes (1.5 × 10⁶/ml) at a ratio of 7:1. The co-incubation assay was performed in the presence of 10% FCS, 10% serum from patients (serum [RA]) or from healthy donors (serum [control]). All data are expressed as percentages of TNF-α produced in the 10% FCS containing co-culture system (100%). Data are means ± SEM for 10 independent experiments; levels of significance are as indicated. (b) Monocytes from healthy donors were preincubated with 50% control sera (nine donors) or RA sera (six sera from patients with RA, which were previously found to inhibit T cell-dependent monocyte activation) and then washed thoroughly three times. Co-culture experiments were performed as described in the text in medium supplemented with 10% FCS. All data are expressed as percentages of TNF-α produced in the co-culture system containing 10% FCS. Data are means ± SEM for four independent experiments; levels of significance are as indicated.