1. Describe how immunisation (passive and active) works, using tetanus as an example.
  2. Describe the humoral immune response.
  3. Give an overview of tetanus, causes and clinical features.
  4. Describe how bacteria can cause infection and name some organisms that can cause superficial wound infection.
  5. Discuss the main classifications of antibiotics and how they work.

What are antibodies, what are antigens?

Antigens are parts of the cellular bodies which stimulate the immuno-response of the body and for their reaction antibodies are required to attack these antigens. Any substance that may be specifically bound by an antibody molecule, in order to generate a specific small molecule and large molecules before immunization, the small molecules is called hapten and the large molecule is called carrier.
There are three major categories they can be classified into:

  • Immunogen: the antigens which are used to provoke immune response
  • Tolerogen: a molecule which creates a specific immune non-responsiveness, if the molecular form is changed then it could become a immunogen.
  • Allergen: this causes an allergic over reaction and it may lead to inflammation or attacking of normal cells inside the body, as the t-cells and neutrophils are having a wrong response.

Antigens are bound to glycoproteins and they have a unique configuration depending on the genes configuration. The gene which is responsible for the is located on chromosome 6 and is called the Major histocompatibility complex (MHC), hence the glycoproteins are called MHC proteins. Each of the MHC proteins has a distinctive 3 dimensional shape, and they are hold onto the membrane through hydrogen bonding.
There are two classes of antigens, one which is responsible for apoptosis and then pagocytosis of the cell after it became abnormal, and secondly the class II which tells the antibodies that this cell is foreign and it should be seen as dangerous hence it needs to be gotten rid off.

  • Class I: The first class uses the cells MHC proteins and they are transported from the vesicles in the golgi apparatus towards the membrane of the cell, if the cell contains abnormal peptides or viral proteins, they will appear on the cell wall and t cell will eventually start attacking them. This is the reason why even the most cross matched DNA can sometimes be rejected as the peptides on the membrane will be covered with foreign antigens.
  • Class II: These antigens are present in lymphocytes and antigen presenting cells (APC), they activate the defense against foreign cells, these antigens are present in all monocyte-macrophage group cells. However they are also present in cells which are not able to phagocyte. The Phagocytic APC engulf and break down the foreign antigens and then release them to their outer membrane, hence the appropriate t-cells can attack the foreign bodies. Lagerhans cells however carry out pinocytosis but still present the antigens of class II onto the cell membrane.

Antigen recognition
Inactive T cells can locate cells with class I or class II MHC proteins as they have special receptors, they have have antigen recognition receptors which are responsible to either find out if a cell has class I or class II MHC proteins, these T cells can be divided into CD (cluster of differentiation) markers there are more than 70 overall however all of them have CD 3 markers however in different T cells there are different Cd markers, like CD8 is present on cytotoxic or suppressor t cells, whereas CD 4 markers are present on helper T cells and antigens.

These are special kind of blood proteins, which are a response to the presence to a particular antigen and circulates in the plasma to attack antigens to make them harmless, hey are diverse as the antigens and usually most of the common antigens can be tackled with this line of defense.
Antigens are made of a heavy chain and a light chain, and the end of the light and heavy chain contains the variable receptors for the binding site on the antigen, minor amino acid sequence changes can affect the precise shape may let the antibody bind to another antigen. A adult has 10 trillion B cells and 100 million and they can produce about 100 million types of antibodies and each has a different specificity.

When antibodies bind to antigens a specific complex is formed and they are held together through hydrogen bonding as well as other chemical bonding. Antibodies don’t attach themselves to the entire antigen, however they attach themselves to specific regions called antigenic determinant sites, their three dimensional shape is the reason why they are variable towards binding and they can fit exactly to a antigen if the antigen has complete antigens through two antigenic determinant sites, one for the antigen binding site and one for the antibody molecules. Most antigens a have multiple different antigen sites on them and they do not necessarily cause B cell to activate themselves if they are not fully developed antigens then b cell activation is not occurring.

The body has five types of immunoglobulins Igs: IgG, IgE, IgD, IgM and IgA. They are structure dependent and however this has no effect on the binding to the antigens as this is made through the binding sites.

What is specific immune response in relation to antibodies?

There are seven different stages for antibody responses.

  1. Neutralization:
The viruses and bacterial sites have specific sites for binding to the cells of the body, antibodies may bind to those sites to disable the attachment of these pathogens to the human cells, this process is called neutralization.

  1. Precipitation and Agglutination:
Each antibody has two binding sites and most antigens have many antigenic determinant sites, hence if two bacteria are in the proximity of a antibody then the antibody will bond to both of the bacteria, however if only one bacteria is near whereas the other is quite distant then the antibody will bond with only one bacteria on both sites. Agglutination occurs if a network of antibody form who are bonded to the bacteria, and this is called the immune complex. When these molecules become insoluble then they can be called precipitation and they agglutinate if the the antigens are on surfaces of virus or cells.

  1. Activation of Conmplex
When antibodies bind they leave one binding site open and change its shape so complement proteins can bind to them, these proteins activate molecules which then destroy the antigen or the cell.

  1. Attraction of phagocytes
Antibodies which cover the antigens attract all leukocytes which have the ability to phagocyte the cell, they in addition phagocytize the abnormal cell.

  1. Opsonization
This process makes the engulfing and disgesting of the foreign cell much easier, as some of the pathogens are have a much smaller membrane and they are not that easy to catch hence phagocytes can bind to the antibodies much easier and digest the overall structure.

  1. Stimulation of Inflammation
They promote inflammation through stimulation of basophil cells.

  1. Prevention of Bacterial and Viral Adhesion
Antibodies dissolve in saliva, mucous and perspiration coat epithelia, this provides additional layer of defense, this makes it harder for the virus or bacterium to attach itself to cells of the body.

What is immunization?
Immunization is acquiring immunity artificially, it can be split into active or passive immunity.
  • Body is exposed to denatured bacteria/virus, and antibodies are formed for attack.
  • These can be bacteria, viruses which remain harmless, while remaining antigenic or completely dead organism, or toxic waste of these organisms, and all of them are chemically or physically altered so they produce a similar effect and production of antibodies
  • These immunization can be lifelong or boosters can be used to increase the number of antibodies
  • Injection of antigens or dead cells ||
  • A serum of antibodies is injected into the recipient so a passive immunity is formed, e.g. in the case of tetanus, antiserum taken from horses is injected into the patients body.
  • These immunizations can be temporary and will not forever, they always require to be re-immunization again.
  • Injection of antibodies. ||

What is tetanus and how do you get immunized against it?

Tetanus is a bacterial infection through spores, and it affects the nervous system as they emit neurotoxins, caused by the bacterium, the clostridium tetani is the reason for the infection. This infection causes the spasms as the muscle fibers as well as the neurosystems are affected by it.
The incubation time of the bacterium is 4-25 days and the symptoms can be muscle, spasm, subsequent rigidity, stiffness, spasm, in the jaw then neck then in the back, chest abdomen and limbs, however it can affect the whole body as well. This is common in mnay developing countries and they are present in unhygienic environment like human or animal faecal matter. It is still the main reason for death in developing countries. You will get immunization every ten years against it, so the immune system is prepared for a infection. The tetanus vaccination is made of modified tetanus toxins and the body can become immune against it.

What are antibiotics and how do they work?

They are derived from microorganism to kill off or inhibit growth of other microorganism, they are mainly used to treat infections and which are usually bacteria and fungi, the bacteria change the microbial content of the body by changing normal or harmless cells/substances into toxic waste products which causes the infection. Usually the bacteria are treated with broad spectrum antibiotics which are useful against most of the pathogens, however some of the bacteria can become resistant to antibiotics as in the case of MRSA, this can be due to overprescription or incorrect dosage of the drug. Antibiotics should not be used to treat minor infections as they clear up on their own, however some antibiotics can cause allergic affects on the patient.
They can be bacteriostatic this inhibits growth or they can be bacteriocidal and these kill of the bacteria.
Some of the antibiotics inhibit cell wall growth and some of the bacteria