FIG 2.

Binding of the COMP-IBD tricomponent complexes to mouse and human Ig isotypes and mouse lymphocytes in vitro. (a) Affinity of the COMP-IBD fusion proteins for mouse and human immunoglobulin (Ig) isotypes. COMP lacking any IBD was used as the negative control. The relative binding strength is expressed as OD₄₁₅. (b and c) Flow cytometric analysis of the COMP-IBDs without (b) or with (c) normal mouse serum. Freshly isolated splenocytes from naive BALB/c mice were double stained with PE-conjugated anti-CD19 or anti-CD3 monoclonal antibody and fluorescein-labeled COMP or COMP-IBDs and then analyzed on a FACSCalibur flow cytometer, as described previously (12). Representative contour plots show the percentage of the fusion complex bound to CD19⁺ B lymphocytes or CD3⁺ T lymphocytes.