KURLOFF CELLS.

Kurloff cells (KB cells) containing a glycoprotein inclusion body appear in female guinea pigs and can be induced in males by oestrogen administration. These cells are found in bone marrow, thymus, and in the red pulp of the spleen, but not in the lymph nodes. Gradually growing inclusion bodies were observed in a series of cells in these organs. Morphological and histochemical features suggested an active synthesis of the inclusion body material: cisternae of the endoplasmic reticulum fused with the membrane surrounding the inclusion body and by way of electron histochemical methods periodate reactive material was demonstrated in the endoplasmic reticulum, in the Golgi cisternae, and in the inclusion body. Enzymatic activities were not observed in the inclusion body, but otherwise the KB cells showed enzymatic activities of oxidative and glycolytic pathways. Marker enzymes for the granulocytes series, the plasma cells, the mast cells, and the monocyte‐reticulum cell group were negative in the KB cells and thus, classification of the KB cells into a particular cell type was not possible, although these cells obviously belong to the lymphoreticuar system. Phagocytosis was not observed, either. The possible role of the KB cells in the immune system are discussed.