LYMPHOID MONOCLONAL-ANTIBODIES REACTIVE WITH LUNG-TUMORS - DIAGNOSTICAPPLICATIONS

In the course of investigating 30 monoclonal antibodies (MAbs) for the ir potential reactivity with 25 lung tumors of different histologic ty pes, we found that three MAbs commonly used for their specificities fo r lymphoid markers were highly reactive with non-small-cell carcinomas (NSCLC) and totally nonreactive with small-cell carcinomas (SCLC). Im munostaining was performed by the standard streptavidin-biotin-peroxid ase method after microwave antigen retrieval on formalin-fixed, paraff in-embedded tissue sections. LN2 (CD74), LN3 (HLA-DR), and BLA-36, whi ch are commonly used for the identification of B-lymphocytes, strongly immunostained 19 of 25 squamous and adenocarcinomas and none of 34 sm all-cell carcinomas and carcinoids. Moreover, in combined tumors, thes e MAbs selectively stained the adenocarcinoma cells but not the adjace nt small-cell carcinoma cells. A cocktail mixture of LN2, LN3, and BLA -36 assayed on 24 additional lung tumors produced similar results with even stronger and sharper stainings. Other lymphoid MAbs showed some selective staining but to a lesser degree. Among nonlymphoid MAbs, the results were as expected, with MAbs for cytokeratin (B72.3) and epith elial membrane antigen staining NSCLC but also some SCLC. The MAbs for chromogranin and neuron-specific enolase were not entirely specific, whereas some nerve-cell adhesion molecule MAbs showed good specificity for SCLC. In a field with few specific MAbs, the newly discovered abi lity of these lymphoid MAbs to dis criminate between SCLC and NSCLC ma y prove useful in the immunohistochemical diagnosis of lung tumors.