Question

Please help me on these two questions for me? It's immunology! Please!!?

1. Describe and explain the main classes of complement activity in the service of the host defense? (In a few sentence or a paragraph)

2. Describe the major steps of class I Endogenous pathway presentation? (In a few sentence or a paragraph)

Thanks,

Answer 1

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Different mechanism involved in the triggering of immune system both innate and adaptive. Among those various processes 2 are discussed here.

Complement system in a host can be activated by three main pathways which are classic, lectin and alternative.
Classic pathway uses C1 and is usually triggered by antigen antibody immune complexes. The C1 later on cleaves into c4 and C2 which again converts into C3 by C3 convertase and then to C5 (C5b-9) the final complement.
The lectin pathway goes exactly same as the classic pathway except for the first step where mannose residues( MBL, MASP) are converted to C4 and C2. Next steps are same as the classic pathway.
In the alternative pathway the starting point would be bacterial toxin aur bacteria where C3 goes to c3b then C3bBb. This goes on again to form 2 molecules of C3bBb then it goes to C5 and then to c5b-9.

Endogenous pathway is the pathway used by the cells to present the peptide fragments of the bacteria or any other microbes on the cell surface on MHC class 1 molecules. Here the major steps would be taking of the bacteria inside cell, digestion of its proteins ,. Transportation of the peptide fragments to cell surface using transporter associated with antigen processing (TAP), then the presentation of these peptides by the MHC 1 molecules for the killer t cells.

Summary: complement it is an important component of the immune system for the defence of the host against various foreign infections etc. These compliments can be activated by different pathways using different components.