Question

Kit Catbury has decided to take a flight to visit her friends in New Zealand. Unfortunately, while on the plane for over 15 hours, the crazy cat lady that sat next to her decided to let Mr. Boots out of his carrier to stretch his legs. Suddenly, Mr. Boots got the "zoomies” and in the process scratched Kit Catbury. This scratch introduced Bartonella henselae, the bacteria responsible for cat scratch fever into her system!

Describe how his adaptive immune system would attempt to fight off a bacterial infection. In your description, you should include the barriers that are normally in place to fight off the bacteria (2 pts), how the bacteria is initially displayed to the adaptive immune system (2 pts for the cell that does it and 2 pts for the receptor used to display the antigen), the type of cell that recognizes this antigen (2 pts for the type of cell and 2 pts for the receptor(s) it uses to interact), how these cells can then activate other cells (2 pts), the cells they activate to fight off the bacterial infection(2 pts) and what they produce to help fight the infection (2 pts), and finally how those products help fight the bacteria (there can be multiple ways, provide one)(2pts). 2 pts for essay formatting, grammar, spelling.

Answer 1

Mr Boots suffering from Bartonella hensale and following inmmunity help in protection against it
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1)When the microbes enter through skin first innate immunity try to eliminate it as skin act as barrier because it is made up of many layers .
Also Phagocytic cells like neutrophils Natural killer cells complement system ,Toll like recetors all of them try to eliminate the bacteria by innate system that is present since birth .
When innate immunity fails to eliminate the pathogen then adaptive immunity comes into play .

2)The critical first step in the elicitation of the adaptive immune response to a primary antigen is the processing of antigen by antigen presenting cells (APC) for the presentation to naive T lymphocytes. Professional antigen-presenting cells (APCs) include , macrophages, and B cells,Dendrites their main function is to load partially degraded peptides into the groove of the MHC class II molecules.

A).Dendritic cells - are the most important APCs, as they do not have to be activated in order to present antigen to T cells. They constitutively express the co-stimulatory molecules needed to activate the naive T helper cells.

B).Macrophages - help activate the Th1 response by digesting microbes and   presenting them to the T cells to elicit a cell-mediated immune response

C).B cells- present specific protein antigens to T cells to help elicit a humoral immune response and form clonal proliferation of antibodies or a Th2 response. B cells are unique, as they are the only APCs that specifically recognize antigen via the B cell receptors (of surface bound antibody).

3)Once antigen is processed and presented to a T cell, the adaptive immune response is initiated. These interactions occur within the secondary lymphoid tissue ( Spleen ,MALT mucosa associated lymohoid tissue and Lymoh nodes ).The purpose of these interactions is to generate effector cells, which will ultimately result in the elimination of the infection. In order to generate specific effector cells, the activation of T cells via the TCR must go through several checkpoints to ensure antigen specificity and eventual T-cell activation.

4)Two most important interactions occuring which act as gate signals for activation of adaptive immune system .
1.First (primary) signal: recognition of the MHC:peptide complex by the T cell receptor and coreceptors (CD4 and CD8)

2.Second (costimulatory) signal: recognition of B7 by CD28

5)Also Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.

6)The Th1 response is characterized by the production of Interferon-gamma, which helps in activation of the bactericidal activities of macrophages and it also , and induces B cells to make opsonizing (marking for phagocytosis) and complement-fixing antibodies, and leads to cell mediated immunity .Th1 responses are more effective against intracellular pathogens (viruses and bacteria that are inside host cells).

Th2 also produce Interleukin 4, which help to facilitates B cell isotype switching.

The Th2 response help to release of Interleukin 5, which induces eosinophils and act against parasites . In general, Th2 responses are more effective against extracellular bacteria, parasites including helminths and toxins.
Like cytotoxic T cells, most of the helper T cells die after the infection is subsided and form memory cells which helps during further infection.

Also B cells produce many antibodies against bacteria and help to get rid of infection .
IgM first antibody to produce
IgD attaches to Bcell and activate it
igG Opsonisation
IGA mucosal immunity Respiratory and GiT
IgE In allergic mast cell mediated reactions .

Therefore these way many cells are interacted with each other to get rid of infection .