Adaptive Immune System or Acquired Immune System or Specific Immune System

As we are moving further in the better understanding of Immune System, today’s blog is about,

·        What is Adaptive Immunity or Acquired Immune System ?

·        How Immune System detects pathogens inside our body ?

·        What Immunity do to meet its goal of being defensive ?

·        How a specific biological or Immunological memory is created ?

·        What are the differences between Innate Immunity and Acquired Immunity ?

Okay Guys!!  No Worries.

In this post we are going to cover each and every biotechnological aspects of Immune System, which in turn will cover all these questions.

We, as humans, are blessed with two types of Immune System. They are,

Ø Innate or Natural Immunity

Ø Adaptive or Acquired Immunity

Innate or Natural Immunity was very well explained in the last post 'Innate/ Natural Immunity' to clear all your doubts.

Here, we will study about the Adaptive or Acquired Immune response for better understanding of Immunity process or Immune System.

Adaptive Immunity or Acquired Immunity  :

Only vertebrates have adaptive immunity.

It ‘remembers’ the previous infection and so has tremendous survival in pathogen filled environment.

Therefore, it is referred to as Adaptive Immunity or Acquired Immunity.

Adaptive Immunity

The adaptive or acquired immune response comprises of   specialized cells and processes to kill pathogens or prevent their attack.

The adaptive immune system is focused towards specific targets.

This immune system provides stronger attacks each time a particular pathogen is encountered.

The major characteristic attributes of adaptive or acquired immunity are:

·        Self and non self recognition

·        Antigenic Specificity

·        Diverse Immunologic memory

1.     Why ‘adaptive’ ?

It is ‘adaptive’ because our natural defender or body’s immune system prepares itself for future pathogenic encounters.

2.     Being ‘specific’ in action :

A layer of protection i.e. adaptive immune system is activated if the pathogen make its way in our body by evading the innate immune system.

Thus adaptive or acquired immune system adapts its response during an infection, in being specific  and improve in reorganization of the pathogens.

3.     Property of memory

After killing or removal of pathogens, B cells and T cells continues their working mechanism, which creates an ‘Immunological memory’.

These cells make adaptive or acquired immune system to work stronger and faster each time there is a pathogenic encounter.

Agents of Adaptive or Acquired Immunity:

The adaptive or acquired immune response work under two types of mechanism. They are :

Ø Humoral Immune response

Ø Cell mediated Immune response

Ø Humoral Immune response :

The production of immunity by administration of antibodies from an immune person.

Ø Cell mediated Immune response:

Immune response produced only by administration of T cells from an immune   individual.

This immune response plays an important role in lysis of tumor cells and virus infected cells.

1.     Cells involved in Adaptive or Acquired Immunity :

Adaptive or Acquired Immune response categorizes the cells involved into two types:

a)    Lymphocytes

b)    Antigen presenting cells

Above mentioned both the cells i.e. (lymphocytes and antigen presenting cells) are explained in previous post 'Cells Of Immune System' , but here we will study then with a different perspective.

a)    Lymphocytes :

The lymphatic system carries infection fighting cells, which are involved in removal of foreign material i.e. pathogens and cell debris known as lymphocytes.

Lymphocytes

The lymphocytes are categorized into two types:

Ø T cells

Ø B cells

Readers can visit my previous post to get into the concepts of T cells and B cells mentioned below.

1.     ImmuneSystem Basic Concepts: Your Natural Defense and Body Cleanser

2.     Innate/Natural Immunity (OUR BODY’S FIRST LINE OF DEFENCE)

3.     CellsOf Immune System

Ø T Cells :

1.     The working process of T cells starts in our body, as soon as they have a combat with the cells.

2.     These cells can be B cells or dendritic cells, which have digested an antigen and are showing antigen fragments linked to T cell’s MHC (Major Histocompatibility Complex) molecule.

3.     The MHC- antigen complex activates T cell receptor and cytokines are secreted by T cell.

4.     These cytokines help T cell to mature.

5.     Some cytokines increase the growth of more T cells.

6.     Some of the T cells become cytotoxic (T_c) and kill viral infected cells.

7.     Some T cells become helper cells (T_h) and secrete cytokines to attract fresh macrophages, neutrophils, other lymphocytes and other cytokines to monitor and direct them, once they reach the site of infection.

The working mechanism can be better understood by the following graphical representation.

T cell Mechanism 

Ø B cells :

B cells create and secrete antibodies which target pathogens and attach with them. This enhances the destruction of pathogens by other parts of immune system.

B cells work in the following pattern:

1.     Antibody (Ab) or Immunoglobin(Ig) receptors present on B cell surface recognize and attach to antigens (Ag) and process of  destruction or deactivation of foreign invaders is activated.

2.     Inside B cell, a fragment of antigen combines with Human Leukocyte Antigen (HLA) class II.

3.     This human leukocyte class II- antigen fragment complex is displayed on B cell surface.

4.     T helper cells (T_h) receptors recognize HLA class II- antigen fragment complex gets activated and produce cytokines, in turn activating B cells.

5.     B cells activated by cytokines start replication or expand clonally.

6.     Some of the B cells become antibody (Ab) producing plasma cells.

Diagrammatically, the process can be explained as follows:

b)    Antigen presenting cells:

These cells are clarified in the previous post 'Cells Of Immune System'

and now we will extend our knowledge to make the topic more logical and understandable.

1.     A pathogen or extracellular antigen (Ag) is phagocytized by an antigen presenting cells or more likely a dendritic cell and gets into a vesicle.

2.     Lysosomes digest the ingested pathogen to extract their antigen.

3.     The antigen binds with the major histocompatibility complex (MHC) protein which enter the vesicle.

4.     The MHC protein having antigens release from the vesicle and travel to the outer surface of cell membrane.

5.     The dendritic cells present antigens (Ab) , which in turn  activates T cells, which bind with the major histocompatibility complex (MHC) protein.

I hope, I have made myself very much clear to my readers in understanding of the topic  “ Adaptive or Acquired Immunity ”.

Moving on, now we will discuss about the major differences between two types of immunity i.e. Innate Immunity and Adaptive Immunity.

Difference between Innate Immunity and Adaptive Immunity :

S.No.	INNATE IMMUNITY	ADAPTIVE IMMUNITY
1.	Found in all forms of life	Found only in vertebrates
2.	First line of defense	Second line of defense
3.	Non – specific response	Antigen specific response to pathogens
4.	Provides immediate action	Lag time in activation
5.	No immunological memory	Possess immunological memory
6.	Effector molecules are cytokines	Antibodies being the effector molecules.

I hope this will clear all your doubts.

I would suggest you to check all my previous posts as well to get the insight of all these topics and help you in forming your basics on Immune System in Biotechnology.

1.     ImmuneSystem Basic Concepts: Your Natural Defense and Body Cleanser

2.     Innate/Natural Immunity (OUR BODY’S FIRST LINE OF DEFENCE)

3.     CellsOf Immune System

Still have lot more to share, Stay connected.

Thank you & Happy Biotechnology Learning!!!

Cells of Immune System in BioTechnology and Immune System

Cells of Immune System

BioTechnology, Immune System

·        Cells of Immune system?

·        Types of cells of Immune system? How these cells provide immunity in our body?

You must have above question in your mind right now. In this post we will cover these questions and discuss about the various cells involved in the immune system machinery.

Cells of Immune system are already well explained in my previous post on Innate or Natural Immunity, please go through it for clear cut picture on Cells of Immune system.

In this post I will explain cells of Immune system individually.

Types of Immune cells:

1.     Lymphoid Cells

2.     Mononuclear Phagocytes

3.     Granulocytic Cells

1.     Lymphoid Cells :

A network of thin blood vessels branch into the tissues throughout our body known as lymphatic system.

This system transports infection fighting cells called lymphocytes.

Lymphoid Cells are further divided into three types of cells-

·        B Lymphocytes

·        T Lymphocytes

·        Natural Killer Cells

All readers can refer my post on Immune System Basic Concepts for clear information on the above mentioned cells.

Let’s proceed with T cells and B cells first,

1.1.         B Lymphocytes:

B cells are a type of white blood cells which produce antibodies.

These cells have a protein on their outer surface known as B cell receptor and play an important role in adaptive immune response.

The main functions of B cells are:

·        They produce antibodies against antigens

·        They perform the role of antigen presenting cells(APC’s)

·        Developing into memory B cells after activation by antigen presentation 

They derive their name from their maturation place. These cells mature into B lymphocytes in bone marrow and so called as B lymphocytes.

1.2.         T Lymphocytes :

It is a type of lymphocyte which plays an important role in immune system by combating the virus infected cells, foreign cells and cancer cells.

These cells mature in thymus, so they are known as T cells.

Receptors present on their cell surface for proper working of these cells are known as T cell receptors and plays a major role in providing immune response.

T cells are sub categorized into the following types/ Types of T cells -

1)    Cytotoxic T cells (T_c cells)

2)    Regulatory T cells or Suppressor T cells

3)    Natural killer cells (NKT cells)

4)    Helper T cells (T_h cells)

5)    γδ T cells

These cells ‘tackle’ the infectious agent and make immune system ‘remember’ the event.

T helper cells produce cytokines which direct the Immune System.

Cytokines in turn signal other immune cells about the presence of an infectious agent.

Cytotoxic T cells come to the rescue and produce toxic granules leading to the death of infectious agent.

Characteristics of types of T cells:

Ø Cytotoxic T cells and Natural killer cells works in accordance in lysis of viral infected cells, tumor cells and allografts (a unit of organ transplantation).

Ø Helper T cells release cytokines and growth factors for regulation of other immune cells.

Ø Gamma/ delta T cells work in process of immunoregulation and cytotoxicity.

1.3.         Natural killer cells :

A subtle information about these cells were explained in Immune System Basic Concepts.

Natural killer cells provide a rapid response to virus infected cells and bacterial cells and more importantly in tumor formation.

In Immunological sciences, there is a saying, “Natural killer cells are unique”.

The reasons behind this statement is,

a)    Ability to recognize stressed cells in absence of antibodies and major histocompatibility complex.

b)    Faster immune response.

Natural killer cells Function:  Natural killer cells have two types of receptor on their cell surface i.e.

§  Activating Receptors

§  Inhibitory Receptors

During Natural killer cells activation, it kills the cell depending on the type of receptor switched on.

Mechanism of Action:

a.     Cytoplasm of NK cells contain protein and enzymes called Granzymes.

b.     These enzymes are released close to the cells, which has triggered their action.

c.      A protein perforin forms pore in the cell membrane of target cells, allowing the entry of enzymes through, leading to the killing of target cells.

2.        Mononuclear Phagocytes:

The briefing of phagocytic process is already provided in the Innate or Natural Immunity

Previously Mononuclear Phagocyte System was known as Reticuloendothelial System.

These phagocytes work in a systemic order to kill pathogen.

Working behavior:

·        The pathogen gets attached or adhere to the plasma membrane of  phagocyte preferably by chemotaxis.

·        The pathogen is ingested by phagocyte.

·        A phagosome is formed around the pathogen.

·        This phagosome gets fused with the lysosome of the phagocyte to form phagolysosome.

·        The digestive enzymes produced kills the pathogen.

·        A residual body is formed for the indigestible material of pathogen.

·        This residual body is discharged off from the phagocytes.

The process of killing of pathogen or phagocytosis is the main centre of study for phagocytes.

3.        Granulocytic Cells:

These are the lymphocytes or white blood cells which have granules in their cytoplasm.

Their nucleus comprises of three segments and they are released from bone marrow.

These cells operate by phagocytosis as well as by other means also.

Types of Granulocytic Cells:

Based on their appearance, these cells are categorized into the following types;

3.1.         Neutrophil Granulocytes

3.2.         Eosinophil Granulocytes

3.3.         Basophil Granulocytes

3.1.         Neutrophils:

They are the most common type of white blood cells and are known as neutrophil granulocytes.

These cells play an important role in immune system and have a very short life span.

Action Mechanism:

§  Neutrophil granulocytes migrate from blood vessels into matrix.

§  On reaching inside matrix, they start secreting enzymes and peptides which dissolve intercellular connections.

§  Dissolution of these connections improves the neutrophil mobility.

§  Being mobile, neutrophils engulf bacteria and kill them through phagocytosis.

3.2.         Eosinophils:

Eosinophils 

These are the granulocytes which combat with parasites and fights infection.

On activation, they release huge amount of proteins like heparin from their granules.

Points to Remember –

·        These cells comprise of bilobed nucleus and are defensive against large multicellular parasites like worms and flukes.

·        The most characteristic feature of eosinophils is that they increase in number during an infection.

·        They are also known as Acidophils.

3.3.         Basophils :

They are referred to as Rare Granulocytes.

Points to Remember –

·        Being a circulating granulocyte, basophils travel from blood into a tissue when needed.

·        They have protein receptors on their cell membrane which binds with IgE, an immunoglobin associated with allergy and macroparasite defence processes.

·        They are found unusually high in number during ectoparasitic infection i.e. by ticks.

·        They carry histamine and heparin for their immunogenic action on pathogens.

·        Mast cells and dendritic cells are also a type of immune cells and work in the following way.

a)    Mast Cells:

A mast cell is a white blood cell which works in tissues.

Points to Remember –

·        It is produced in bone marrow, and matures in tissues, to defend against parasites.

·        Mast cells have granules which contain histamine and heparin.

·        They play a protective role in healing wounds and defence against pathogens.

·        They are a major reason of allergy and anaphylaxis.

·        The mast cell is very similar in appearance and function to the basophil, however, they are not the same.

b.    Dendritic Cells:

Dendritic Cells are known as immune helper cells.

These cells serve three functions mainly,

·        Phagocytosis

·        Antigen presentation

·        Cytokine production.

Phagocytosis is the process of uptake of microbes, their digestion and destruction.

Microbial fragments that remain after digestion act as antigens. This process is called antigen presentation and activates T lymphocytes.

They make a specific immune response against the antigen.

Other microbial products activate these cells and leads to the production of pro-inflammatory cytokines.

So, the topic “Cells of immune system” comes to an end here, hoping to clarify the doubts of all the readers.

Hope this post on ‘Cells of Immune System’ helped you to understand the topic clearly.

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Happy Learning and Good Luck !!!