Question

write a HAIKU for immunology about barrier, so the Haiku should be about barrier.

Answer 1

Immunological Barriers include the defense system our body employs to protect from the pathogens which are encountered in every minute. Our body's defense system may be divided into two catagories called Innate Immune system and the second one is Adaptive Immune system. Innate immune system is present in an individual just from the birth including Physical and chemical barriers which forms the first line of defense for the body against the invading pathogens. These include Skin, Tears, Saliva, mucus, Stomach acid, urine flow, cilia, inner lining of gastrointestinal tract and respiratory tract, cilia, friendly bacteria and some white blood cells called neutrophils. Apart from these there are also mechanical barriers as well like the waxy cuticle of most leaves, the exoskeleton of insects, the shells and membranes of externally deposited eggs are examples of mechanical barriers that are the first line of defense against infection.  In the lungs, coughing and sneezing mechanically eject pathogens and other irritants from the respiratory tract thus acting as a barrier.

Chemical Barriers include:

The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins. Enzymes such as lysozyme and phospholipase A2 in saliva, tears, and breast milk are also antibacterials.Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while semen contains defensins and zinc to kill pathogens. In the stomach, gastric acid and proteases serve as powerful chemical defenses against ingested pathogens.

In humans, the blood–brain barrier, blood–cerebrospinal fluid barrier, and similar fluid–brain barriers separate the peripheral immune system from the neuroimmune system, which protects the brain.

Nonspecific Resistance (Innate Immunity):

The second line of defense is nonspecific resistance that destroys invaders in a generalized way without targeting specific individuals:

• Phagocytic cells ingest and destroy all microbes that pass into body tissues. For example macrophages are cells derived from monocytes (a type of white blood cell). Macrophages leave the bloodstream and enter body tissues to patrol for pathogens. When the macrophage encounters a microbe, this is what happens:
  1. The microbe attaches to the phagocyte.
  2. The phagocyte's plasma membrane extends and surrounds the microbe and takes the microbe into the cell in a vesicle.
  3. The vesicle merges with a lysosome, which contains digestive enzymes.
  4. The digestive enzymes begin to break down the microbe. The phagocyte uses any nutrients it can and leaves the rest as indigestible material and antigenic fragments within the vesicle.
  5. The phagocyte makes protein markers, and they enter the vesicle.
  6. The indigestible material is removed by exocytosis.
  7. The antigenic fragments bind to the protein marker and are displayed on the plasma membrane surface. The macrophage then secretes interleukin-1 which activates the T cells to secrete interleukin 2, as described below under specific resistance .
• Inflammation is a localized tissue response that occurs when your tissues are damaged and in response to other stimuli. Inflammation brings more white blood cells to the site where the microbes have invaded. The inflammatory response produces swelling, redness, heat, pain
• Fever inhibits bacterial growth and increases the rate of tissue repair during an infection.

Specific Resistance (Acquired Immunity)

The third line of defense is specific resistance. This system relies on antigens, which are specific substances found in foreign microbes.

Most antigens are proteins that serve as the stimulus to produce an immune response. The term "antigen" comes from ANTI-body GENerating substances.

Here are the steps in an immune response:

1. When an antigen is detected by a macrophage (as describe above under phagocytosis), this causes the T-cells to become activated.

   The activation of T-cells by a specific antigen is called cell-mediated immunity. The body contains millions of different T-cells, each able to respond to one specific antigen.

2. The T-cells secrete interleukin 2. Interleukin 2 causes the proliferation of certain cytotoxic T cells and B cells.
3. From here, the immune response follows 2 paths: one path uses cytotoxic T cells and the other uses B cells.

Cytotoxic T Cell Pathway

• The cytotoxic T cells are capable of recognizing antigens on the surface of infected body cells.
• The cytotoxic T cells bind to the infected cells and secrete cytotoxins that induce apoptosis (cell suicide) in the infected cell and perforins that cause perforations in the infected cells.
• Both of these mechanisms destroys the pathogen in the infected body cell.

Activation of a helper T cell and its roles in immunity:

T Cell Pathway

• T-cells can either directly destroy the microbes or use chemical secretions to destroy them.
• At the same time, T cells stimulate B cells to divide, forming plasma cells that are able to produce antibodies and memory B cells.
• If the same antigen enters the body later, the memory B cells divide to make more plasma cells and memory cells that can protect against future attacks by the same antigen.
• When the T cells activate (stimulate) the B cells to divide into plasma cells, this is called antibody-mediated immunity.

Antibodies

Antibodies (also called immunoglobulins or Ig's) are Y-shaped proteins that circulate through the blood stream and bind to specific antigens, thereby attacking microbes.

The antibodies are transported through the blood and the lymph to the pathogen invasion site.

The body contains millions of different B cells, each able to respond to one specific antigen.

There are 4 classes of antibodies (listed from most common to least common):

• IgG
• IgM
• IgA
• IgE
• IgD

Each antibody is made of four polypeptide (protein) chains: 2 heavy chains and 2 light chains. Both heavy chains are identical to each other and both light chains are identical to each other. Each contains a constant region and a variable region. The constant region forms the main part of the molecule while the variable regions forms the antigen-binding site.Each antibody has 2 antigen-binding sites.

Antibodies work in different ways:

1. Neutralizing an Antigen

The antibody can bind to an antigen, forming an antigen-antibody complex. This forms a shield around the antigen, preventing its normal function. This is how toxins from bacteria can be neutralized or how a cell can prevent a viral antigen from binding to a body cell thereby preventing infection.

2. Activating Complement:

Complement is a group of plasma proteins made by the liver that normally are inactive in the body. An antigen-antibody complex triggers a series of reactions that activates these proteins. Some of the activated proteins can cluster together to form a pore or channel that inserts into a microbe's plasma membrane.This lyses (ruptures) the cell. Other complement proteins can cause chemotaxis and inflammation, both of which increase the number of white blood cells at the site of invasion.

3. Precipitating Antigens

Sometimes the antibodies can bind to the same free antigen to cross-link them. This causes the antigen to precipitate out of solution, making it easier for phagocytic cells to ingest them by phagocytosis (as describe above).

Also, the antigens within the cells walls of the bacteria can cross-link, causes the bacteria to clump together in a process called agglutination, again making it easier for phagocytic cells to ingest them by phagocytosis.

4. Facilitating Phagocytosis

The antigen-antibody complex signals phagocytic cells to attack. The complex also binds to the surface of macrophages to further facilitate phagocytosis.

There are 3 major types of T cells:

1. Cytotoxic T cells

These cells secrete cytotoxin which triggers destruction of the pathogen's DNA or perforin which is a protein that creates holes in the pathogens plasma membrane. The holes cause the pathogen to lyse (rupture).

2. Helper T cells

These cells secrete interleukin 2 (I-2) which stimulates cell division of T cells and B cells. In other words, these cells recruit even more cells to help fight the pathogen.

3. Memory T cells

These cells remain dormant after the initial exposure to an antigen. If the same antigen presents itself again, even if it is years later, the memory cells are stimulated to convert themselves into cytotoxic T cells and help fight the pathogen.