Question

List the different classes of antibodies, where they are found and their functions

Answer 1

Ans.

• Immune systems of our body release specialized protein products in circulation, which are called as antibodies, upon sensing a danger.
• They help in providing protection to body from infectious pathogens such as virus, bacteria and infected cells also.
• Each of the antibody respond by binding to a specific target, called as antigen, associated with the stimulatory danger signals.
• There are 5 different types of antibodies known in our body.
• These different types are also classified into different isotypes and classes.
• The production of different types of antibody isotope depends upon the location of infection inside the body.
• The five different types of antibodies being produced in our body are;

1). IgG -

• It is the most common type of antibody being produced in body.
• This antibody is produced as a result of immunization, located in lymph and blood and can even cross pacenta.
• It is the most abundant type of antibody being produced with accounting for about 70-75% of total antibodies being produced.
• It is diveded into several subclasses ; IgG1, 2, 3 & 4.
• Immune pathway activated by this antibody can inhibit many types of infection and it can even neutralize many toxins.
• It can also increase phagocytosis in macrophages and neutrophils.

2). IgA -

• This antibody is commonly found in mucosal areas (mouth and vagina), saliva, tears and breast milk.
• It is formed as a result of association of two subunits of Ig and is accounted for about 15% of total antibody load.
• IgA leads to the inflammation upon binding to a target antigen and prevent the attachment of pathogens to epithelial cells.
• IgA can also be inappropriately produced in certain disease conditions suc as celiac disease.
• It acts as an important gatekeeper in physically susceptible locations.

3). IgM -

• After a pathogen infection, this antibody appears as one of the first line defence.
• It is formed by the binding of five subunits of Ig which is responsible for it's high avidity.
• It plays a crucial role during the initial stages of infections and also provide in certain cases of reoccurance of infections and diseases.
• It is mainly found circulating in blood and lymph nodes, making up about 10% of total antibody load of our body.
• It stimulates lysis and phagocytosis of many microbes, especially bacteria.

4). IgE -

• This antibody is commonly located in the lungs, skin and mucous membranes and is responsible for mediating allergic responses.
• Plasma cells found in lymph nodes make this antibody and it's amount is less then 1% in our body.
• It leads to a histamine reaction upon binding an allergen and this histamine reaction is responsible for leading to the allergic symptoms.
• It is a single subunit antibody and also act to protect body from parasitic worms.
• It also provide an indirect immune response by stimulating other components of immune system.

5). IgD -

• This antibody also plays a crucial role during the early stages of infections.
• It is found attached to the B cells (plasma membrane of immature of B-lymphocytes) and is not found free in the circulation.
• Due to it's attachment to the B cells, this antibody signals the activation of B cells and thereby stimulate inflammation.
• It is found in least amount ( less then 1%) in body and it's exact functions are still not clear.
• This antibody is responsible for several autimmune responses.