Human lymphocytes that produce anti‐pneumococcal antibodies were separated and immortalized by Epstein‐Barr virus and then cloned. One clone (NAD‐Sel) produces an IgA, x antibody which is specific for the polysaccharides of type 8 pneumococcus, while not reactive with any of the polysaccharides derived from 24 other pneumococcal strains. The antibody, which is present in the cell supernatant as monomer and polymer, binds to protein A and does not fix complement. When incubated in vitro with type 8 pneumococci, it induces direct killing and increases the opsonization of these bacteria by mouse macrophages.