immunology complement system

The____ and _____ pathways are not absolutely required for defense against infections.

lectin and alternative

Opsonins that bind to surface of microbes

"b" fragments (C3b & C5b)

complement in synthesized in what organ?

liver

All of the following processes can be activated by complement except A) inflammation B) antibody production C) cytolysis D) opsonization E) none of the above

B

Complement factors C5b+C6+C7+C8 make up a membrane attack complex that results in A) enhanced phagocytosis B) opsonization C) cytolysis D) all of the above

C

The most abundant complement protein in plasma is _______ and it plays a central role in all 3 complement pathways.

C3

Anaphylatoxins

C3a and C5a

What does the membrane attack complex do?

Creates a pore in a cell membrane of the target cell to cause lyse

Opsonization is A) a membrane attack complex lysing a bacterium by making a hole in its membrane B) when complement causes inflammation to occur C) when the nine complement factors cascade in order D) coating of a bacterium with antibody to make it more susceptible to phagocytosis

D

Somewhat surprisingly, deficiencies of the _____ proteins of the ________ pathway, ____ and _____, do not cause immune deficiencies.

Deficiencies of the early proteins of the classical pathway, C2 and C4, may have no clinical consequence

Deficiency of ____ results in profound susceptibility to _______ and is usually _____ in early life.

Deficiency of C3 results in increased susceptibility to bacterial infections that may be fatal early in life.

Why is the complement system effective against microbes but does not react against host cells & tissues?

Mammalian cells express regulatory proteins that inhibit complement activation, thus preventing complement-mediated damage to host cells

A macromolecule that becomes attached to surface of a microbe that can be recognized by surface receptors of neutrophils and macrophages to increase efficiency of phagocytosis of microbes.

Opsonin

___________ is probably the most important function of complement in defense against microbes.

Opsonization

What happens in the late steps of complement activation?

The late steps of complement activation are initiated by the binding of C5 to the C5 convertase and subsequent proteolysis of C5, generating C5b (Fig. 8-10). The remaining components, C6, C7, C8, and C9, bind sequentially to a complex nucleated by C5b. The final protein in the pathway, C9, polymerizes to form a pore in the cell membrane through which water and ions can enter, causing death of the microbe. The C5-9 complex is called the membrane attack complex (MAC), and its formation is the end result of complement activation.

What is the end result of the early steps of complement activation?

The net result of these early steps of complement activation is that microbes acquire a coat of covalently attached C3b. Note that the alternative and lectin pathways are effector mechanisms of innate immunity, whereas the classical pathway is a mechanism of adaptive humoral immunity.

Normally, these proteins are inactive in the sera

Zymogens

Complement plays an essential role in inflammation and ________ effectiveness

antibody

Complement functions to produce _________ ______ fragments for lysis or killing of microorganisms

biologically active

The most common complement deficiency that causes immune complex disorders

c2

system of serum and cell surface proteins that interact with one another and with other molecules of the immune system to generate important effectors of innate and adaptive responses

complement

Complement factors are named in the order in which they function. A) True B) False

false

after the C5 convertase, the late steps are _____ in all pathways

same

How is the lectin pathway triggered? Does it need antibodies for activation?

triggered by the attachment of plasma mannose-binding lectin (MBL) to microbes. no

How is the classical pathway triggered? Does it need antibodies for activation?

triggered when IgM or certain subclasses of IgG (IgG1, IgG2, and IgG3 in humans) bind to antigens yes

How is the alternative pathway triggered? Does it need antibodies for activation?

triggered when a breakdown product of C3 hydrolysis, called C3b, is deposited on the surface of a microbe no

In the classical pathway of complement activation, complement attaches to an antigen-antibody complex. A) True B) False

true