The immune system and vaccines

Dr Maxwell Adeyemi

The immune system fight germs and foreign substances in the body and it is made up of two parts that work closely together by taking on different tasks.

The innate immune system

This is the body’s first line of defence against germs entering the body. It responds in the same way to all germs and foreign substances hence it is often called general or “non-specific” immune system. It acts quickly and ensures germs are detected and destroyed within a short space of time, but it has only limited power to stop germs from spreading.

The innate immune system consists of:

• Skin and mucous membrane, which form physical barriers against germs, also consist of chemicals like acids, enzymes and mucus that prevent germ entry.

• Immune system or defence cells are activated when germs get past the physical barrier, these cells cause inflammation, blood vessels get wider and more permeable, the area affected get swollen, hot and red. A fever may develop, more blood vessels expand, and more immune cells arrive the area. Scavenger cells known as phagocytes, a special kind of white blood cells or leucocytes attack the germs and neutralise them.

• Protein and enzymes are usually released to help the innate cells. Up to nine different enzymes and inflammatory substances are released and allows the immune system responses to escalate quickly to destroy germs.

• Natural killer cells destroy germs and infected cells by using cell toxins.

The adaptive or acquired immune system

This takes over when the innate system is unable to destroy the germ. Otherwise known as specific or acquired immune system, it specifically targets the type of germ causing the infection. It first identifies the germ, then attacks it. This immune system is slow to respond but is very accurate and has the advantage of being able to remember germs so that if it encounters the specific germ again, it will respond swiftly to neutralise or destroy it.

The adaptive immune system consists of:

• T-cells are produced in the bone marrow and stored in the thymus gland. They can be specialised into cytotoxic T-cells that detect and destroy germs and T-helper cells that use chemical messengers to activate other immune cells that start the adaptive immune system. They then become memory T-cells that can remember cells after infections has been defeated. The immune system can produce a matching T-cell type for each germ, once a germ attaches to the matching T-cell, it multiplies rapidly creating more T-cell specialised to that germ.

• B-cells are produced in the bone marrow and matures into specialised cells. B-cells are activated by T-helper cells, they also multiply and transform into plasma cells, which quickly produce large amounts of antibodies. Some of the activated B-cells transform into memory cells and become part of the adaptive immune system. The various adaptive immune system communicates directly or by chemical messengers such as cytokines – small proteins produced by different cells in the body.

• Antibodies are produced be B-cells and can act quickly to detect and kill germs. When germs or harmful substances (antigen) enters the body, they provoke the production of antibodies. Antibodies attaches to antigen and creates a fast response from the adaptive immune system. These antibodies neutralise the germ, activates other immune system cells and proteins that help the immune system response.

The T cells produced by the bone marrow and stored in the thymus usually respond to foreign intruders (virus, bacteria) and take them to the lymph nodes, located in the axilla, neck, groin.

B-cells also attack, multiply themselves and make specific memory cells to attack the specific germ whenever they come in contact with it again.

The process of activation of these system takes about two weeks. To avoid severe consequences of the body being overwhelmed with resultant fatal result, the body can be given a “heads up” by vaccination, so it can be equipped to fight before infection is contracted, especially if the body comes across a dangerous germ (like covid) that can cause great damage before adaptive immunity is activated.

Types of vaccines

Development of vaccine uses various methods and technology, from the past as well as new innovations.

• Live attenuated virus vaccine: This uses paralysed or attenuated virus to prompt the body to activate an immune response, this method is used for measles polio, mumps and tetanus vaccines.

• Killed or inactivated virus vaccine: The virus is chemically inactivated so it cannot replicate but all the proteins remain intact. The inactivated virus is then able to produce an immune response in the body. This is the technology used in Sinopharm vaccine. It is an already used technology and many flu shots are also produced by this method.

• Viral vector vaccine: This method used another virus that is not harmful, to human to introduce a characteristic feature of the virus at stake into the body to trigger immune response. The covid19 virus has a characteristic “spike protein” on its head. An adenovirus is used as a viral vector and a safe carrier, and DNA encoding of the spike protein is introduced into the cell. The infected cell then expresses the spike protein and “tricks” the body into believing the covid virus is in the cell, thus causing the body to activate the immune response. The Johnson and Johnson vaccine and the Astra Zeneca vaccines used this technology.

• Encapsulated mRNA vaccine: This method used by Moderna and Pfizer, utilised the mRNA encoding for the spike protein, which is then protected by a phospho-lipid “nano” or tiny particle. It then introduces this spike protein into the cell, and once absorbed, the cell expresses the spike protein and triggers an immune response.

Once any of these vaccines get into the body, they activate the adaptive immune system, mount up antibodies against the covid19 virus so that if you come in contact with the real virus, your body is able to prevent severe illness, hospitalisation or death. Any of the available vaccines are capable of building immunity against covid19.

Contact Dr Maxwell on 363-1890 or 757-5411.