Enables IgA binding activity and protein-macromolecule adaptor activity. Contributes to immunoglobulin receptor binding activity. Predicted to be involved in several processes, including defense response to other organism; glomerular filtration; and positive regulation of respiratory burst. Part of dimeric IgA immunoglobulin complex. Is expressed in intestine; serum; and spleen. Orthologous to human JCHAIN (joining chain of multimeric IgA and IgM). [provided by Alliance of Genome Resources, Apr 2022]