[A new pan-macrophage antibody Ki-M1P stains plasmacytoid cells in paraffin sections of lymph nodes].

Plasmacytoid, T cells (PTC) occurring in cases of chronic non-specific lymphadenitis were investigated using a panel of monoclonal antibodies and cryostat sections. From the typical T cell antigens only CD4 was detectable on PTC. Antibodies directed against myelo-monocytic antigens such as Ki-M2, Ki-M6 (CD68), and Ki-M7 revealed positive reaction with these cells. The recently established monoclonal antibody Ki-M1P reactive with monocyte/macrophages shows a surface and granular cytoplasmic reactivity with PTC. This observation may indicate the myelo-monocytic origin. Ki-M1P detects a formalin resistant antigen and is thus applicable to conventionally processed paraffin sections as demonstrated in twenty cases of hystiocytic necrotizing lymphadenitis (KIKUCHI).