Figure 6.

Increased proportion of dimeric and polymeric IgA in sera of β4GalT-I^−/− mice was observed. A and B: Serum proteins from β4GalT-I^+/− (A) and β4GalT-I^−/− (B) mice at 25 weeks of age were fractionated by gel filtration and the IgA levels in each fraction were measured. Arrowheads indicate 440 kd, and arrows indicate 150 kd. C: Fractions 16, 20, and 25 of the A (+/−) and B (−/−) samples were separated by electrophoresis under reducing conditions, and Western blot analysis was performed using anti-mouse IgA α-chain antibody. D: Western blot analysis of the same samples in C separated by electrophoresis under nonreducing conditions.