Question

Describe the activation of the complement system making sure to list the three major outcomes. Give two examples of mechanisms by which a parasite we discussed in lecture evades complement activation.

Answer 1

Complement system is part of immune systems that enhances the ability of antibodies and phagocytic cell to clear microbes and damaged cells from an organism.It is a part of innate immune system .It consists of numerous small proteins that are synthesized by liver and circulate as inactive precursor .It is made up of large distinct plasma proteins that react with one another to opsonize pathogen induce a series of inflammatory response that help in fighting off infection.

There are mainly three pathways for activation of Complement system-

And the activation of the activation of the complement system are -

1 Generation of large numbers of activate complement proteins that bind covalently to pathogens opsonizing them for phagocytosis by phagocytes .

2 The small fragments of the complement proteins act as Chemoattractants to cause recruitment of more phagocytes to the site of complement activation and also causes activation of these phagocytes.

3 The terminal complement components damage certain bacteria by creating pores in the bacterial membrane

Mechanism used by parasites to evade complement activation-

To survive within the host the parasite must evade the activation of the complement system or else it will cause damage to the parasite so the parasite uses several method to evade the activation of complement system of which 2 are given below-

1 There is expression of proteins to capture host regulatory proteins .By this mechanisms the parasite captures the complement protein released by the host immune system so that it will not lead to activation .

2 There is production of proteins that are similar or homologous to the host regulatory proteins and these homologous proteins compete with the host regulatory protein for binding with complement receptors and inhibit activation and functioning of the host complement system