Figure 3.

Analysis of the composition of IgA forms secreted by clones 22, F, and 6. Two hundred microliters of crude SN was separated by chromatography on a Superose 12 column (Pharmacia) equilibrated and run in PBS. Fractions of 250 μl were collected and analyzed by ELISA (α-chain and SC) or Western blot (J chain). For ELISA, the resulting OD at 492 nm is plotted. For Western blot analysis, half of the fraction was concentrated by TCA precipitation before loading on a 15% polyacrylamide/SDS gel. After transfer, the protein was detected with rabbit anti-J chain antiserum, followed by mouse anti-rabbit antibody conjugated with HRP and chemiluminescence. Films were scanned by using an Elscript 400-AT/SM densitometer, and values were plotted with the strongest intensity arbitrarily fixed as 100%.