Question

outline how the innate, humoral, and/or cell-mediated immune responses would deal with an extracellular, encapsulated bacterium or a virus that infects epithelial cells. For both infections assume that this is the first time that the person has been infected. Be sure to include cell types and molecules (antibodies [note the isotype], complement pathway, etc) that would be involved in pathogen clearance.

Answer 1

The innate immunity is a series of non-specific defense mechanism which takes its role immediately or within hours after the entrance of infection of a pathogen which is activated by the chemical properties of the antigen. Iti is the first-line host defence specified to confine infection in the early hours immediately of after a few hours after exposure to the pathogen. It includes many anatomical barriers such as lysozymes in the saliva, different pH in the stomach and other organs, ear wax, high salt levels in the sweat and other organs secreting different chemicals that help in killing the invading pathogens. However, if the invading pathogen still survives these anatomical barriers , Certain phagocytes such as macrophages or dendritic cells respond by engulfing the virus by phagocytosis. Many viruses have proteins bound on their capsid called PAMPs that are recognized by PRRs found on Toll-like Receptors upon internalization. Signal induction pathway will then be initiated ultimately leading to the production of NF-KB or IRF transcription factors. These transcription factors then enter the cell nucleus where they activate the transcription genes which are then transcribed to cytokines These cytokines are exocytosed from the cell. Macrophages produces many types of cytokines which includes IL-I beta, TNF alpha, IL-6 in which they are associated with many functions gradually leading to inflammatory response caused by the releasing of these cytokines which further kills these pathogens. Other cells which involve includes the NK cells, the Complement system which activates a cascade of proteolytic reactions (Opsonization) along with the help of the classical pathway to generate the inflammatory response. In the case of Humoral immunity, it is the immune response that are mediated by antibodies that are produced by plasma cells of B-cells in body fluids such as lymph,etc,. The first step here is the B-cell activation where the antigen binds to the Naive B-cell receptor. It has a B-cell receptor that has a specificity for a particular pathogen. It has MHC Class 1 receptor and also MHC Class 2 receptor as it is an Antigen Presenting Cell. Another Naive B-cell with a different specificity, specifically different epitopes of different pathogens interferes with the first Naive B-cell. If a viral particle is bound to the B-cell receptor, this causes the activation of the first Naive B-cell. Then occurs the activation of that activated B-cell through Clonal Selection with the same specificity and numerous B-cells are produced within the system. After this step, Differentiation takes place where the divided cells thus produced differentiated into plasma cells and memory B-cells. The plasma cells produces antibodies that bind to the antigen and the memory B-cells for immunologic memory or secondary response and are finally released into the blood stream. If the same or another infection occurs later, the antibodies,, thus produced will kill and eat up the invading pathogens through phagocytosis which will be specific with the help of the memory B-cells.