Question

Question: Complement plays key roles in the elimination of bacteria. Bacteria must develop strategies to overcome these activities in order to survive. A. Identify three major roles of complement. (these are the answers i found for this part.) 1.) opsonization and phagocytosis 2.)cell lysis 3.) chemotaxis B. For EACH of the three roles, identify ONE complement element which is responsible for that role and explain how that complement element is formed. C. Propose a bacterial evasion strategy (known or potential) that might realistically be employed to divert or prevent the formation of EACH of these three elements. D. Choose ONE of these evasive maneuvers and suggest a possible counter-strategy the immune system might employ to overcome it.

Answer 1

A. WHAT IS MEANT BY COMPLEMENT? It is a system of the innate immune response and a complex system of more than 30 proteins that act to eliminate the infectious micro-organisms. ROLE OF COMPLEMENT IN OPSONIZATION AND PHAGOCYTOSIS: - C3b, C4b and C1q are the important complement proteins that mediate with opsonization. - Its spontaneous action convert C3 to C3b, an antigen surface. - Antibodies can also activate complement through classical pathway by depositing C3b and C4b on to the antigen pathway. - After C3b binds with antigen surface, it signals for phagocytosis. ROLE OF COMPLEMENT IN CELL LYSIS: Pathways of complement activation. The main function of complement proteins is to aid in the destruction of pathogens by piercing in to their outer membranes to phagocytic cells. ROLE OF COMPLEMENT IN CHEMOTAXIS: Deactivation of chemotatic factors to other complement- derived chemotactic factors results in deactivation of all the other responses. B. COMPLEMENT ELEMENT FOR OPSONIZATION: C3b - C3b is a potent opsonization. It plays a role in forming a C3 convertase when bound to factor B complex molecule forming an element. The C3 convertase functions as a postive feedback loop and more C3 convertase formed. When it increased in numbers, it amplifies signal on the surface of the microbial invader. It acts as a powerful tool for the immune system in effective clearance of the invading pathogen. COMPLEMENT ELEMENT FOR CELL LYSIS: IgM or IgG- initiates the classical pathway leads to assembly of C3 convertase.The C3b interacts with parent C3 convertases to form C5 convertases to initiate the terminal lytic pathway and it bound by complement receptors forming phagocytes.   COMPLEMENT ELEMENT FOR CHEMOTAXIS: C5b-9 In the classical pathway,C1 binds with Fc fragments of IgM or IgG and forms a complex of antigen. This immuno-globulin mediated antigen uses the ability of immunoglobulin to detect and bind to non-self antigen. This binding helps to identify enemies more clearly. C. COMPLEMENT EVASION BY OPSONIZATION: The co-existence of humans and micro-organisms has generated a fascinating interplay of mechanisms that maintain the balance between infection, defence and evasion. However, this balance is changed in favour of the pathogenic intruders. The other factors such as cell adhesion, colonization efficiency avoiding the attacks of the immune system is a key determinant of microbial survival inside a host environment. The complement protein targets the Staphylococcus aureus as a target for immune escape. D. A POSSIBLE STRATEGY FOR IMMUNE SYSTEM: To function an immune system,it needs balance and harmony. There are a direct link with lifestyle and immune response. Researchers are exploring the effects of diet, exercise, age, psychological stress and other factors responsible for immune response in humans. A healthy immune system can defeat the invading pathogens results in the large phagocyte called neutrophil, that engulfs and kills the bacteria. To adopt a helthy living strategies should follow certain best step for a good helth guidelines. They are a) donot smoke b) eat a diet high in fruits and vegetables c) execise regularly d) maintain a healthy weight e) avoid drinking alcohols f) get adequate sleep g) handwashing frequently h) reduce stress.