Fig. 5.

Preferential assembly of class II/Ii complexes with increased class II/CLIP affinity. Western blotting was used to detect proportions of I-A^g7β (using 10-2.16 antibody) and transfected, His-tagged Ii (using anti-Tetra His antibody) in whole cell lysates (A, 10⁶ live cell equivalents) or in class II/Ii complexes IPed from whole cell lysates by 10-2.16 (B, anti-I-A^g7β IP from 10⁷ cell equivalents) or by anti-Tetra-His (C, anti-His-tagged Ii IP from 10⁷ cell equivalents) antibodies. In (B), the I-A^g7β and His-Ii bands are indicated by arrows. In the I-A^g7 blot (upper panel), the lower band is the light chain of the 10-2.16 antibody used for the IP, recognized by the goat-anti-mouse IgG2b–HRP secondary reagent in the western blot. In the anti-His blot (middle panel), the upper band is a non-specific band sometimes detected by the anti-Tetra-His antibody, detectable upon lengthy exposure of the film. One representative experiment of three is shown. Densitometry was performed as described in Methods.