Transplantable immunoglobulin‐secreting tumours in rats. I. General features of LOU/Ws1 strain rat immunocytomas and their monoclonal proteins

This article describes a peculiar tumour which originates in the ileocoecal lymph node of the LOU/Ws1 strain rat. The tumour cells usually have the appearance of very poorly differentiated lymphoid cells showing a tendency to develop ribosome‐studded ergastoplasmic membranes. In about 60% of the cases, such tumours synthesize monoclonal immunoglobulins of the IgG or IgA class, or Bence‐Jones proteins. These tumours are readily transplantable in isologous hosts or their F hybrids. The great majority of the transplanted growths retain their capacity for immunoglobulin production during many successive passages in vivo. A scrutiny of older and more recent literature has revealed several descriptions of rat tumours having the same macroscopic and microscopic features as the tumours described here, except for the immunoglobulin‐secreting properties which were never tested in the earlier studies. It is proposed to call this tumour the rat ileocoecal immunocytoma.