What Is the Membrane Attack Complex?

MAC (membrane attack complex) refers to the membrane attack complex produced after complement activation in immunology.

MAC

(Membrane Attack Complex)

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MAC (membrane attack complex) refers to the membrane attack complex produced after complement activation in immunology.

Chinese name

MAC

Foreign name

membrane attack complex

Brief introduction

Membrane attack complex

Function

Lyse cells

MAC (membrane attack complex)

In immunology refers to the membrane attack complex produced after complement activation

In the terminal pathway of the complement activation pathway, C5b can stably bind to C6 to C5b6, which spontaneously combines with C7 to form C5b67. C7 in this complex is initially inserted into the lipid bilayer of the target cell membrane, and then C8 is inserted into C5b67 on the membrane High affinity binding to form a stable C5b678 deeply inserted into the cell membrane. This complex can be combined with 12 to 18 C9 molecules to form C5b6789n, which is the membrane attack complex.

Observed under an electron microscope, MAC is a hollow C9 polymer, which penetrates the lipid bilayer membrane of the target cell to form a transmembrane channel with an inner diameter of about 11 nm. This channel allows free flow of water, ions, and soluble small molecules across the membrane, while intracellular colloid osmotic pressure is higher than extracellular, so a large amount of water flows in, resulting in a decrease in intracellular osmotic pressure, and the cell gradually swells and eventually ruptures (ie, the cell " Dissolve ").

The MAC inserted into the cell membrane forms a "leakage spot" by destroying the local phospholipid bilayer, or forms a hydrophilic pore through the membrane, eventually causing the cell to collapse.