Evidence for the Origin of Plasma Cells from Adventitial Cells : I. Sensitized Subcutaneous Connective Tissue Examined by Light Microscopy

Arthus reactions were induced in the dorsal skin, and the subcutaneous connective tissues from the sensitized areas were examined at various stages. The subcutaneous connective tissue was used due to its simplicity of construction and because it could be studied conveniently by both supravital and fixed methods. This combination of tissue and technic allowed both an accurate classification of various types of inflammatory cells and a close examination of their relationships to the blood vessels.

Cells transitional between adventitial cells and plasma cells were observed after antigenic stimulation. Their location on the walls of the venules and capillaries indicated that they were adventitial cells but their morphology was that of plasma cells. By supravital technic they exhibited a glassy and homogeneous cytoplasm, a circular formation of neutral red granules, and a diffuse distribution of Janus green granules; and by fixed method they exhibited a chromatin pattern similar to that of plasma cells, an increased cytoplasmic basophilia, and a nucleolus was often present. Small plasma cells appeared simultaneously around the venules and capillaries. The local origin of plasma cells would appear to explain the absence of plasmacytosis during strong tissue plasma cell reactions.

Immunofluorescence was only found in plasma cells and in transitional adventitial cells, indicating a functional similarity between the 2 cells.