LSA120 MAb is directed against a lung cell antigen. It shows a well-defined reactivity with cells of the lung lineage at all stages of maturation. Non-lung lineages are negative by immuno-histology. Although the exact identity of its antigen has yet to be determined, it has been shown to be distinct from MOC-52 and UM-A9 proteins. This MAb is useful in the identification of normal and neoplastic human lung cells.