Question

Discuss the immune response to an extracellular bacterial pathogen. Include the branch(es) of the immune system which would mount the response, how that response would be mounted, and the major effector functions that would be observed. While you should include information on the innate immune response to your chosen pathogen, the bulk of your response should be focused on the adaptive immune response.

I'm looking for a 1-2 pages response, but anything will help, thanks!

Answer 1

Innate immune system :-
It includes the mechanical barriers that cover the body surfaces and the cells that acts on initial internal battlefronts which are present at place from the birth which ward off pathogens and infections.
This is also known as first line body defence and includes following
The skin has thick layer of dead cells in the epidermis which provides a physical barrier
The mucous membranes produce mucus that trap microbes.
Hair within the nose filters air containing microbes, dust, pollutants
Cilia lines the upper respiratory tract traps and propels inhaled debris to throat
Urine flushes microbes out of the urethra
Defecation and vomiting -expel microorganisms.
Lysozyme, an enzyme produced in tears, perspiration, and saliva can break down cell walls and thus acts as an antibiotic (kills bacteria)
Gastric juice in the stomach destroys bacteria and most toxins because the gastric juice is highly acidic (pH 2-3)
Saliva dilutes the number of microorganisms and washes the teeth and mouth
pH on skin-Acidity on skin inhibit bacterial growth
Sebum (unsaturated fatty acids) provides a protective film on the skin and inhibits growth
Hyaluronic acid is a gelatinous substance that slows the spread of noxious agents

Adaptive immunity:- The adaptive immunity is also called as acquired immunity. Its activity tremendously amplifies the inflammatory responses and responsible for complement activation. The adaptive immune system is divided into natural and artificial immune system.
Natural immune system is further divided into active(infection-contact with pathogens) and passive (antibodies pass from mother to foetus through placenta)
Artificial immune system is further divided into active(vaccines- dead or attenuated pathogens) and passive (injection of immune serum or gamma globulin)
It can be specific, systemic and has memory.
Humoral immune system is a antibody mediated immune system which is provided by antibodies present in extracellular fluids like lymph, blood etc.
these antibodies circulate freely in blood and lymph and bind to bacteria, to bacterial toxins and to free viruses in turn inactivating them temporarily and are destructed by the phagocytes or complement.
Sometimes lymphocytes themselves defend the body against the pathogens rather than antibodies. They lyse the foreign cells or release chemical mediators that enhance the inflammation response or activates other lymphocytes or macrophages.
Most naturally occurring antigens have variety of antigenic determinants which mobilise several lymphocyte population and stimulates the formation of many kinds of antibodies.
The external surfaces of the cells contains variety of protein molecules called as class 1 MHC and class 2 MHC. These MHC proteins also bind to fragments of antigens and mobilise the immune system.
During an immune response, a specific T cell is activated and begins to enlarge and divide to form a group of cells called a clone. The cells differentiate into four different types. Each of these has a different role to play during the immune response. During maturation T cells receive one or two sets of surface proteins either CD4 or CD8 proteins. The appropriate B cell is turned on or stimulated. It then grows bigger, and rapidly multiplies into a large homogenous group (clone). Most of these cells are plasma cells, which actively secrete antibody that will bind with the original stimulating antigen.

The cells and molecules of adaptive immune system are given as follows and their in immune response
B cells – lymphocytes that resides in lymph node, spleen, or other lymphoid tissues, where it is induced to replicate by antigen binding and helper T cell interactions; its progeny forms a memory and plasma cells
plasma cells – it is a antibody producing machine which produces large number of antibodies with the same antign specificity
helper T cells – stimulates production of cytotoxic T and B cells to fight invaders by releasing the cytotoxins.
Cytotoxic T cells – these are killer cells. It kills viruses invading the body and cancer cells.
Suppressor T cells – slows or stops activity of B and T cells once infection has been conquered.
Memory cells – are generated during primary response and quickly respond if the body encounters same pathogen again.
Antigen-repressing cells – one of the several cell types that engulf and digest antigens that it encounters and presents part of them on plasma membrane.
Antibody – these are the proteins produced by the plasma cells and attach to the antigen and causes complement fixation, neutralization, precipitation, which marks the antigen for destruction by complement.
In this way the the antigen entering into body is destroyed and body is protected from infections.