Antibody-producing cells have been identified among cells obtained from efferent lymphatic vessels, the thoracic duct, and peripheral blood. These cells, which produced plaques of hemolysis and which were quite rare (20 to 50 per million), due in most instances to 19S antibody, were located and studied by electron microscopy.
Of the antibody-producing cells found in these three sites there were several features common to all: small size (5 to 8 µ), generally spherical shape, approximately central position of the nucleus, and retention in the nucleus of the condensations of chromatin characteristic of the lymphocyte.
The differences among the cells of these sources were largely in the relative amount and state of organization of the organelles of the cytoplasm. In cells of the efferent lymphatic vessel and the thoracic duct, the endoplasmic reticulum showed a range from relative scarcity to considerable numbers of well organized channels. Between these extremes were cells with a considerable amount of endoplasmic reticulum, the channels disorganized and sectioned at various angles. The cytoplasmic matrix of all of these contained a profusion of polyribosomes. Antibody-producing cells obtained from peripheral blood showed, around the roughly spherical nucleus, a ring of cytoplasm which was narrow, but wholly organized into parallel lamellae of endoplasmic reticulum, with many polyribosomes between these, and a large Golgi body.
Some similarities and some differences of these cells, in comparison with antibody-producing cells obtained from lymph nodes, have been indicated.