Question

Complement System - Host Resistance to Viral Infections

1. In what 3 ways does complement contribute to clearance of viruses (effector functions)?

a. What complement proteins are directly involved in each of these defenses?

Answer 1

The complement system is also known as the complement cascade is a part of immune system which enhances (complements) the ability of antibodies and phagocytes to remove microbes and damaged cells from an organism.It promotes inflammation and attacks the pathogen's cell membrane. Viruses can be removed from body by antibodies before they get chance to infect a cell. A virus-bound antibody binds the receptors called Fc receptors,on the surface of phagocytes and triggers a mechanism called phagocytosis by which cells engulf and destroys the virus. The 3 ways by which viruses are removed by complement system includes 3 broad effector pathaways.1.lysis 2.inflammation 3. Opsonization or phagocytosis . 1Direct neutralisation of the cell free virus.

2.lysis of virus infected cells acheived by cytotoxic t lymphocytes, natural killer cells and antiviral macrophages.

3. Boosting of virus specific immune responses.

answer of question a. Lysis specific proteins are expressed such as (holin).

Virus infected cells secretes small antiviral proteins called interferons which protects non infected cells.