Peanut agglutinin: a new marker for tissue histiocytes

The histiocyte (macrophage) is a unique cellular constituent of the immune system which is involved in immune and non-immune cellular reactions, as well as in the genesis of a variety of benign and malignant neoplasms. The ability to distinguish histiocytes from similar appearing cells morphologically, is often difficult, yet may be of considerable practical and theoretical importance. The present study describes a new marker for histiocytes, applicable to routinely processed tissues. An immunoperoxidase procedure to detect binding of peanut agglutinin (PNA) was applied to 58 specimens consisting of lymph nodes, extranodal lymphoid tissues, neoplasms and reactive histiocytic lesions. Results were compared with a currently accepted histiocytic marker--cytoplasmic muramidase. Of the 58 tissues, 51 showed PNA binding to morphologically recognizable histiocytes, whereas muramidase was detected in only 44. PNA binding- appeared at least as sensitive and specific as muramidase, as a marker for histiocytes, and offers the advantage that it does not bind to cells of the granulocytic series.