Comparative immunostaining of T-associated plasma cells and other lymph-node cells in paraffin sections

The immunoperoxidase technique after trypsinization was used on paraffin sections of 24 lymph nodes with reactive lymphadenitis and abundant nests of T-associated plasma cells. These cells were negative for all the markers investigated, which were: intracytoplasmic immunoglobulins (CIg), a1-antichymotrypsin(a1-ACT), a1-antitrypsin(a1-AT), lysozyme(Lz) and fibronectin. Other categories of cells were positive or negative depending on their type. The best markers for polymorphs proved to be a1-AT and Lz, and for monocytes and histiocytes a1-ACT and Lz. Sinus histiocytes in particular were much more constantly and strongly positive for a1-ACT than for Lz. Endothelial cells appeared almost always positive for a1-ACT and were also occasionally positive for a1-AT. Fibronectin was consistently positive in mast cells and sometimes positive in other cells, especially those of monohistiocytic origin. Our present findings are against a B-cell or monohistiocytic origin for T-associated plasma cells.