Plasma Cell Morphology
Stained with hematoxylin and eosin, plasma cell nuclei stain bluish-purple, with purplish-pink cytoplasm. MGP stained the cytoplasm pinkish-red and the nuclei bluish-purple. Characteristics of the plasma cells were that they have large irregular eccentric nuclei, with prominent nucleoli close to the center of the cell, a larger clear cytoplasmic area adjacent to the cell's nucleus, with a large transparent-like, clear cytoplasm which stained and lost its' transparency in areas distant to the nucleus, where the Golgi apparatus, endoplasmic reticulum and the abundant mitochondria are known to be present.
Many morphological changes are seen when a naive B cell differentiates into a plasma cell. These changes reflect the plasma cells commitment to the sole production of large amounts of secreted antibodies. Pathological tissue sample slides provide a suitable means of visualizing the morphology and characteristic features of plasma cells.
Nasal polyps are nasal epithelia outgrowths as a results of type I hypersensitivity reactions, caused by inflammation involving IgE antibody triggering of mast cells. Moreover, these reactions recruit numerous leukocytes, including large amounts of plasma cells to the site of infection. However, these plasma cells are usually difficult to characterize. Use of electron microscopy can easily enable for more detailed and more profound visualization of plasma cells. However, several plasma cells should be found (1).
Overall, plasma cells are seen as large, spherical or ellipsoidal cells, with abundant cytoplasm, an eccentrically, not at the center, located oval nucleus, surrounded by a perinuclear zone (8).
Fixed tissue samples of plasma cells can reveal large, eccentric, darkly staining irregular nuclei, with numerous different stains. Greater detail of the nucleus can be seen with an H and E stain. The dark staining of the nucleus is due to the peripheral chromatin condensation because of plasma cells do not proliferate, and therefore do not need extensive DNA as they do not transcribe from many sequences. The majority of the chromatin is packed into a silent form. There is evidence of prominent nucleoli as rRNA is being largely syntehsized for protein antibody production.
There is a large amount of transparent, clear cytoplasm, that is dominated by a weak staining patter, which is believed to be indicative and characteristic of multiple layer of rough endoplasmic reticulum, prominent Golgi apparatus and abundant mitochondria, with frequent vacuoles clearing the cytoplasm. A characteristic clearing next and also perinuclear, to the nucleus in the cytoplasm is thought to be the beginning of the rough endoplasmic reticulum. The multiple and diverse spanning layers of rough endoplasmic reticulum (rER) are required for the extensive and active antibody (protein) production. In addition, the MGP stain contains pyronin, which stains RNA pink. The cytoplasm of the plasma cells were well stained, indicating the presence of RNA. Moreover, plasma cells are known to be basophilic and pyroninophilic, having affinity for and binding to basic dyes. The rER are knwon to contain a large amount of the antibodies in their cisternae (not visualized). This light staining is thought to be indicative also of abundant mitochondria, which have their own genetic material and are also known to be present at high concentrations within actively-protein synthesizing cells, producing the required ATP for antibody production. The Golgi in plasma cells is full of antibodies, as plasma cells secrete antibodies, which it transports to the cell membrane for their terminal secretion. The darker staining, adjacent to the clearing next to the nucleus and close to the cell membranes, is where the Golgi apparatus resides, as its' function is to transport the proteins made in the rER to the cell surface. Plasma cells also have no surface immunoglobulins and no MHC class II molecules (1).
References:
1. Janeway, C.A., Travers P., Walport M., and Capra J.D. 1999. Immunobiology: The immune system in health and disease. Garland Publishing, 4th ed., New York, USA, pages 1-40, 2.5-2.22, 3.1-3.12
2. Kissinger R, and Myl A.D. 1984. Improvements to the Plaque Assay for Antibody Secreting Cells. J. of Immun. Meth. 66:377-382
3. Wilson S., Munson A., and Meade J. 1999. Assessment of the Functional Integrity of the Humoral Immune Response: The Plaque-Forming Cell Assay and the Enzyme-Linked Immunosorbent Assay. Methods 19:2-7
4. Cunningham, A.J. 1965. Nature (London) 207, 1106
5. Cunningham A.J. and Szenberg A. 1968. Immuniligy 14: 599
6. Jerne N. and Nordin A. 1963. Science 140: 405
7. Delves P. and Roitt I. 1999. Encyclopedia of Immunology, Academic Press Inc., 2nd ed., San Diego, USA page 238.
8. Cruse, J and Lewis, R. 1995. Illustrated Dictionary of Immunology. CRC Press Inc., USA pages 1960-1965