Plasma cells are key to the immune response because they secrete antibodies. Given that antibodies are made of proteins, which membrane-enclosed cell organelle would you expect the plasma cells to have abundance? Why?
The Correct Answer and Explanation is:
Correct Answer: Rough Endoplasmic Reticulum (Rough ER)
Plasma cells are specialized white blood cells that play a crucial role in the immune response by producing and secreting large quantities of antibodies. Antibodies are proteins, and their synthesis, folding, and modification involve various cellular organelles. Among these, the rough endoplasmic reticulum (rough ER) is particularly abundant in plasma cells.
The rough ER is a membrane-bound organelle studded with ribosomes on its cytoplasmic surface, which gives it a “rough” appearance under a microscope. These ribosomes are the sites of protein synthesis, especially for proteins that are secreted from the cell or incorporated into membranes. In plasma cells, the rough ER is highly developed because of the high demand for antibody production. The ribosomes attached to the rough ER synthesize the polypeptide chains of antibodies, which are then translocated into the ER lumen for folding and post-translational modifications.
Once the antibodies are synthesized in the rough ER, they are transported to the Golgi apparatus for further modification, packaging, and secretion. However, the initial and major site of synthesis is the rough ER. The extensive development of the rough ER in plasma cells ensures efficient production of the large amounts of antibodies required to neutralize pathogens during an immune response.
In summary, the rough ER is the most abundant organelle in plasma cells due to its essential role in synthesizing and processing the vast quantities of antibodies these cells produce. This specialization reflects the relationship between a cell’s structure and its function: cells that produce proteins for secretion, like plasma cells, are structurally adapted with an abundance of rough ER to support their function effectively.
