THE IMMUNE SYSTEM NEW DEVELOPMENTS IN RESEARCH (RECOGNIZING INVADERS)

Hello friends how you guys doing i hope everyone is fit and fine before writing today's blog which will be based on "how our immune system recognize the invaders" we will discuss about the legendary scientist who passed away the great STEPHEN HAWKING  (8 January 1942 – 14 March 2018)

Stephen Hawking was diagnosed with Amyotrophic Lateral Sclerosis at the age of 21.

*Stephen Hawking* Born on Galileo’s 300th death anniversary. Died on Einstein’s Birthday.

Sthephen Hawking's life was a great inspiration

REST IN PEACE!

At last you can watch the glimpse of Stephen Hawking's life in the movie "The theory of Everything"

Let's begin our today's topic which is..

RECOGNIZING INVADERS PART

So, our immune system is very effective in getting rid of pathogens or other types of invaders.

Then, how do we recognize such invaders?

What kind of strategies does our immune system exploit to recognize them?

Now, let us study the basic terminology to understand this issue.

First of all, an antigen refers to any substance that provokes an immune response.

This word originally came from ANTIbody GENerator, ANTIGEN, meaning that antigen is the

molecule that can generate antibodies or the molecule that can induce antibody responses in

the body.

Pathogens normally have a number of such antigens on their surface; they are proteins, sugars

or lipids.

In addition, these molecules have a number of determinants or epitopes; an epitope is the part

of an antigen that is recognized by the immune system.

Against these antigenic determinants or epitopes, immune cells have structures necessary for

sensing, and these structures are collectively called sensors.

Basically any type of immune cells has such sensors, and hence, they are able to recognize

molecules or cells invading into our body.

Mechanism of non-self recognition

Functionally speaking, our immune system can be subdivided into two.

One is the innate immune system that provides non-specific host defense against invading

pathogens, whereas the other is the adaptive immune system that provides specific and longlasting

immunity.

The former, the innate system is natural or "innate" to the host, and is ready to respond to

invasion and does not require a period of time for induction.

Once pathogens invade our body by breaching the skin or mucous membrane barriers, the

innate immune system is immediately activated.

As we will discuss later, the major cellular components of this system include macrophages,

neutrophils, dendritic cells and natural killer cells.

If the innate immunity could not eliminate pathogens, another immune system, which is called

the adaptive or acquired immune system, is activated, and specific immune responses occur.

This system is highly specific and acquired in nature.

Most importantly, the major players of the adaptive immune system are lymphocytes such as T

cells and B cells, T lymphocytes and B lymphocytes and their products.

The reason why activation of the innate immune system promotes induction of the adaptive

immune system is because activated cellular components of the innate immune system such

as dendritic cells and also cytokines produced by the activated cells act on lymphocytes to

stimulate their proliferation, differentiation, and survival.

This slide shows you what I just mentioned.

Following microbial invasion, the innate immune system, consisting of epithelial barriers,

macrophages, neutrophils, dendritic cells, natural killer cells and so on, and also complement

components that I will explain more later, plays a major role in pathogen elimination.

Innate immunity starts to act immediately after pathogen invasion and

continues to act for many hours.

When the invading pathogen is not satisfactorily eliminated, adaptive immunity ensues.

B lymphocytes proliferate recognizing the pathogen antigenic determinants and finally produce

antibodies, which block infection and eliminates the pathogen.

When the pathogen invades the cytoplasm, T cells recognize the pathogen with the aid of

dendritic cells.

In the picture you can see the dendritic cell and this is a T cell.

This leads to the recognition of the pathogen, and finally eradicates the intracellular microbes.

Full-blown adaptive immune responses thus require several days.

Here I show you the major cellular components involved in innate immunity.

Some of them engulf pathogens; Macrophages, neutrophils, dendritic cells.

They are called phagocytes and others act as effector cells, releasing bactericidal proteins or

proteins that can kill microbes, and some act as cytokine producing cells.

Cytokines, such as G-CSF, IL means interleukin, IL-1, IL-6.

They mediate inflammatory and immune reactions, and are principal mediators of

communication between cells of the immune system.

A recent addition to the innate immune system is a group of cells, here, innate lymphoid cells or

ILCs.

We know now that there are, at least, three types of ILCs.

They all secrete cytokines that can activate immune cells including T and B lymphocytes.

So, in this system, you have many different kinds of cells and they secrete bactericidal proteins

and cytokines.

Most ... Quite few of them are called interleukins.

I hope the blog enhanced your knowledge about Immune system in next blog we will get more info about recognizing invaders so stay tuned and read as much as you can ..