There are only a handful of situations that we can say globally affect our lives, the most obvious being war. But at least in a war, you can sense who or what is trying to do you harm! The Covid-19 pandemic sees us apparently under attack by an enemy shrewd enough to evade the the senses we rely on daily for protection; sight, sound, smell, taste, and touch.

Prior to the onset of the current pandemic had you spent much time thinking about your own immunity? Had you discussed it with friends or family? Maybe occasionally, if ever. Now, for many of us it seems to have become an everyday discussion!

For most, regardless of what part of the world we live in, this pandemic has us questioning the best ways to protect ourselves and our families. So what is immunity? What does it do? Where is it? Is ours working well? Is there something we can do to support it? Let's try to offer some clarity...

In reality, we are bombarded daily by bacteria, viruses, parasites and more, all trying to infiltrate our defences and cause us pain, illness, and suffering, and for the most part we are totally unaware this is even happening.

Immunity is often described as a battle between two teams, the good guys versus the baddies... Well it's not quite that simple, in fact we have an amazingly complex set of systems to protect us; oh yes, there's more than one!!

Our immune system is a network of cells, tissues, and organs with the collective and sole function of reducing the incident and or likelihood of infection and/or disease.

Lifelong Immunity

Literally meaning 'from birth', the innate immune system is present and functional from birth, and impressively it also remains with us for life. This innate system has a full complement of co-operating members to assist us in maintaining our health by fighting off infection and disease. These members include, white blood cells, acids, enzymes, as well as certain physical barriers, the most visible and obvious being our skin (the body's largest organ).

Innate immunity is a non-specific system of defence. In other words, it attacks anything and everything it considers a potential threat. This can be seen as both a blessing and a curse...

On the plus side, the innate system does not attempt to memorise what specific threats look like, or learn how to deal with them. Meaning when faced with an invader, no time is wasted recalling this information and recruiting the perfect defence team to combat the particular pathogen. Instead it jumps to action very quickly. Reacting indiscriminately to any invader potentially trying to cause harm... a speedy little ally!

For some, this hasty, lack of specificity can lead to problems however, as evidenced by allergies (alongside other reactions). As the innate system has no reference library for specific invaders, and treats all perceived threats equally, it can at times result in extreme reactions to seemingly harmless elements. An allergic reaction occurs when the innate system assesses that a relatively innocuous invader such as food, pollen, or dust poses a threat and initiates a defensive response. For some this results in minor discomfort, but for others this misjudgement can be life-threatening.

Another example is auto-immune conditions, whereby the immune system believes that part of itself is an invading pathogen and mounts an attack. There are over 80 recognised auto-immune conditions including rheumatoid Arthritis, Lupus, and Crohn's Disease, to name but a few.

The response from the innate immune system is not particularly potent when compared to other types of immune response...

Acquired or Adaptive Immunity

As its name suggests, the adaptive or acquired immune system is something which develops in response to exposure. This system of immunity is not actively functioning when we are born, instead it develops as and when our bodies are exposed to pathogens.

Unlike the innate system, acquired/adaptive immunity is specific in its response, in other words it only responds to a pathogen it recognises. The process of learning and recognition takes time; following the first exposure to an invader, it may take as long as 14 days for the immune system to mount it's defence response, explaining why we might not feel symptoms straight away. This process is duly named a cell mediated response as it is the white blood cells themselves which communicate and pass on information to each other for the sole purpose of building a defence strategy. Here's a (very) condensed overview...

• A pathogen invades, passing all barriers to gain entry

• The pathogen enters a cell, multiplies and infects other cells causing infection or disease

• The innate immune system amounts an attack but cannot contain the invader

• Information is pass by macrophages (white blood cells from the innate immune system) which consume pathogens to T helper cells (CD4) of the acquired or adaptive immune system

• T helper cells in turn pass on information relating to the invading pathogen to other T cells once recognition has been made

• Aptly name cytotoxic killer cells (CD8) multiply and initiate a defence response

• B cells also react and multiply, growing in size to develop plasma cells

• Plasma cells produce antibodies and amount an attack on the invading pathogen

• B cells and T cell develop memory cells which recognize the specific invading pathogen for future defence

When compared to the innate immune system, acquired/adaptive response is slow on first exposure to a pathogen, although more potent. Generally however, once the body has been exposed to a pathogen and a memory of it has been created, second or third exposures are much quicker and stronger in response. The length of time this memory to a specific pathogen lasts for can vary however. It could be a relatively short time, decades, or for life. This is why oftentimes, when we receive immunisations a booster a booster injection is required - these can help to lengthen the memory.

A Perfect Complement

Another element supporting our immunity is the complement system.

Complement immunity consists of a group of 20-30 plasma proteins which are made in the liver. This system is actually part of our innate immunity and is with us from birth. Opposed to what we have already learned about innate immunity however, the complement system only functions, once activated by a pathogen. There are three pathways for activation; the classical pathway, the bacterial pathway, and the lectin pathway.

The effects of each pathway

• Opsonization , white blood cells called neutrophils and macrophages are activated resulting in pathogen being engulfed (consumed)

• Cell lysis, or membrane attack where the out-cell membrane of a bacteria is ruptured by complement proteins destroying the cell

• Chemotaxis, a process where macrophages are attracted to the site where pathogens are present to mount an attack

• Another process is where white blood cells called mast cells and basophils are activated which, in turn, mediate an inflammation reaction

Our immune system is made up of many elements, this includes the skin, the thymus, the spleen, the lymphatic system, and lymph nodes, as well as an array of white blood cells.

The age and general health of an individual may hinder or assist in the effectiveness of our immunity.

As with all health and fitness matters we must play our part in assisting our bodies. The immune system is no different, there are things we can do to both assist and to hinder its function and our body's defence. For further information check out our Quick Tips - Ways to Support Your Immunity HERE.