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Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B cells [1] [2] and secrete large quantities of proteins called antibodies in response to being presented specific substances called antigens.
B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. [1] They function in the humoral immunity component of the adaptive immune system. [1] B cells produce antibody molecules which may be either secreted or inserted into the plasma membrane where they serve as a part of B-cell receptors. [2]
Between the xylem and phloem is a meristem called the vascular cambium. This tissue divides off cells that will become additional xylem and phloem. This growth increases the girth of the plant, rather than its length. As long as the vascular cambium continues to produce new cells, the plant will continue to grow more stout.
Unlike xylem (which is composed primarily of dead cells), the phloem is composed of still-living cells that transport sap. The sap is a water-based solution, but rich in sugars made by photosynthesis. These sugars are transported to non-photosynthetic parts of the plant, such as the roots, or into storage structures, such as tubers or bulbs. [14]
Primarily, phloem carries dissolved food substances throughout the plant. This conduction system is composed of sieve-tube member and companion cells, that are without secondary walls. The parent cells of the vascular cambium produce both xylem and phloem. This usually also includes fibers, parenchyma and ray cells.
Sieve cells are long, conducting cells in the phloem that do not form sieve tubes. The major difference between sieve cells and sieve tube members is the lack of sieve plates in sieve cells. [1] They have a very narrow diameter and tend to be longer in length than sieve tube elements as they are generally associated with albuminous cells. [4]
Contrary to popular belief, haemoglobin is not a blood protein, as it is carried within red blood cells, rather than in the blood serum. Serum albumin accounts for 55% of blood proteins, [ 1 ] is a major contributor to maintaining the oncotic pressure of plasma and assists, as a carrier, in the transport of lipids and steroid hormones .
BCDFs control the advancement of a B cell progenitor or unmatured B cell to an adult immunoglobulin (Ig) secreting cell. Differentiation factors control cell fate and can sometimes cause matured cells to change lineage. Not all currently known BCGFs and BCDFs affect all B cell lineages and stages of the cell cycle in similar ways.