Plasma Cells

Plasma cells, plasmocytes (Plasmazellen), were first described by Unna (1891) in granulations of lupus and simultaneously by Ramon y Cajal in condylomas. However, the term P. k. had already been used earlier by Waldeyer (1875) to denote various cellular forms. When distinguishing P. k. as a special type of cell, Unna based his classification solely on the basophilia of the protoplasm and therefore also included other cells of granulation tissue, for example, so-called polyblasts. The first precise description of P. k. and their differentiation from other cells of granulation tissue belongs to Marschalko (v. Marschalko, 1895). Since then, P. k. have been understood to mean only P. k. 'of the Marschalko type,' or P. k. in the proper sense. For detecting P. k., basic dyes (polychrome methylene blue, thionin, toluidine blue) are particularly suitable, as well as the Romanowsky and methylgrün-pyronin mixture of Pappenheim. The size of P. k. is very variable; on average they range from 6 to 16 μ in diameter. Their basic form is round or oval, but in tissues under the pressure of adjacent elements, they often take on a polygonal, sometimes even elongated shape; their contours are mostly even, with rounded corners; their ability for amoeboid movement is very weakly expressed [see separate table, vol. XXIV (pp. 223-224), fig. 3]. The nucleus is relatively small, round or oval, located eccentrically; the nuclear membrane is sharply defined, and on its inner surface lie coarse, rounded (sometimes triangular) dark chromatin particles at almost equal distances from each other. The latter sometimes lie at the ends of radially arranged linin threads (the so-called 'wheel-shaped' nucleus-'Radkern'). Sometimes an oxyphilic nucleolus is noticeable in the nucleus. Figures of karyokinesis are rarely encountered in P. k.; amitotic division of nuclei is much more common, especially in large specimens of P. k., which is considered a manifestation of 'aging' of the cells. Often 2 or more nuclei are found in P. k. The cytoplasm of P. k. is homogeneous in the living state; after fixation it is indistinctly coarse-grained and sharply basophilic. To the side of the nucleus or surrounding it is a clearly defined light field ('heller Hof'), representing an attraction sphere; in the latter, a group of centrioles can be detected. No inclusions are found in P. k. except for occasional vacuoles (in larger cells); plastosomes have been described as grains and threads. According to the generally accepted view, P. k. develop from small and medium lymphocytes of both blood and tissue origin, which is proven by the frequent presence of transitional forms from lymphocytes to P. k., as well as observations on lymphocyte cultures (Maximov). The origin of 'atypical' P. k. from large lymphocytes (lymphoblasts or myeloblasts-hence 'lymphoblastic' P. k. of Schridde), monocytes, and polyblasts is also admitted. P. k. have been found in representatives of all classes of vertebrates, especially in subcutaneous connective tissue and in serous membranes. Almost all authors consider P. k. to be unstable forms incapable of further transformations. Degeneration, pyknosis of nuclei are common in them; the protoplasm either becomes vacuolated or homogeneous coarse acidophilic bodies appear in it, taking a round shape and often lying freely in the tissue after cell disintegration (the so-called Russell bodies). Some describe P. k. with basophilic metachromatic granulation (the so-called 'Plasmamastzellen'). The functional significance of P. k. is unclear: some attribute to them a secretory function, others the formation of protective bodies, and still others participation in the processing of products of tissue disintegration. P. k. occur in normal loose connective tissue only in small numbers, mainly along blood vessels; they are more numerous in the omentum, in the stroma of various glands (mammary, salivary), in the intestinal mucosa, and in lymph nodes. In the blood, according to the opinion of most clinical hematologists, P. k. appear in certain diseases (acute infections, leukemias) in the form of the so-called 'forms of irritation' of Türk. The largest number of P. k., often entire clusters, are found in granulation tissue, especially in chronic purulent inflammation (e.g., in purulent gonorrheal salpingitis, soft chancre, actinomycosis), and further in the specific granulation tissue of syphilis (both in initial sclerosis and in papules and gummatous infiltrates, more rarely in gummas). A constantly large number of P. k. is found in the adventitial spaces of small vessels of the cerebral cortex in dementia paralytica, in the infiltrates of the aortic wall in syphilitic mesoarteritis, and in the kidneys in congenital syphilis. P. k. are found less constantly and in much smaller numbers in tuberculous granulations. They are found in large numbers in leprosy, rhinoscleroma, beriberi (in the meninges), in the conjunctiva in spring catarrh, in the walls of the intestine and stomach in catarrhs, in the spleen in various acute infections, and finally in the stroma and around epithelial tumors, both benign (e.g., in skin and mucous papillomas) and malignant. In rare cases, tumor-like proliferations of P. k. are observed, belonging to the so-called plasmocytomas (see).