C3a (complement)

C3a is one of the proteins formed by the cleavage of complement component 3; the other is C3b. C3a is a 77 residue peptide that binds to the C3a receptor (C3aR) a class A G protein-coupled receptor. It stimulates mast cell degranulation, thus triggering an immune response. Though traditionally thought to serve a strictly pro-inflammatory role, recent investigations have shown that C3a also works against C5a to serve an anti-inflammatory role.

C3a plays an important role in chemotaxis, though not as important a role as C5a.

It is also an anaphylatoxin and the precursor of the important cytokine (adipokine) ASP through its interaction with carboxypeptidase B. Because C3a is rapidly degraded in serum, stable small molecule agonists and antagonists may be used as tools to probe the physiological effects of C3a in vivo.

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Complement

Complement may refer to:

Mathematics and physics

Complement system

The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear pathogens from an organism. It is part of the innate immune system, which is not adaptable and does not change over the course of an individual's lifetime. However, it can be recruited and brought into action by the adaptive immune system.

The complement system consists of a number of small proteins found in the blood, in general synthesized by the liver, and normally circulating as inactive precursors (pro-proteins). When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages. The end result of this complement activation or complement fixation cascade is massive amplification of the response and activation of the cell-killing membrane attack complex. Over 30 proteins and protein fragments make up the complement system, including serum proteins, serosal proteins, and cell membrane receptors. They account for about 10% of the globulin fraction of blood serum and can serve as opsonins.

Ship's company

A ship's company comprises all officers, non-commissioned officers and enlisted personnel aboard a naval vessel. The size of the ship's company (the complement) is the number of people on board, excluding civilians and guests.

An exception to this rule is the definition of ship's company as it applies to U.S. Navy and U.S. Marine Corps personnel assigned to aircraft-capable ships of the U.S. Navy, primarily aircraft carriers and amphibious assault ships.

In the case of aircraft carriers of the U.S. Navy, the total ship's complement is divided into three categories:

(1) the ship's company physically assigned to the ship, and
(2) the carrier air wing, with its associated strike fighter, Marine fighter/attack, electronic attack, airborne early warning and helicopter squadrons, which is considered a separate "embarked" command, and
(3) the carrier strike group commander and staff, which is also considered an "embarked" command