Human Immune Systems Against Infections Biology Essay

One of the most critical parts of the human organic structure is the immune system, responsible for protecting against legion different infections and foreign encroachers ; such as bacteriums, viruses and Fungis. The immune system has many different lines of defense mechanism to fit itself to dispute the encroachers. This could be considered as an onslaught on a palace, in this instance the organic structure is the palace and the immune system is the ground forces protecting the palace. The palace is systematically at menace of invasion by antigens, whilst our ground forces works difficult to offer changeless protection without our cognition.

The first line of defense mechanism, is for the immune system to forestall the encroachers, known as antigens from come ining the palace. This is done through the usage of physical and chemical barriers. The palace is protected by the tegument and mucose membranes. The tegument is capable of releasing perspiration and sebum which combine together to organize muramidases which break down the cell wall of any bacteriums which are found keeping on to the exterior of the palace, looking for a manner to come in.

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When the outer bed is integral, encroachers are unable to come in the palace, nevertheless on occasion gaps in the defense mechanism arrive ; the olfactory organ, eyes, oral cavity, unfastened lesions, etc. These are protected by the fosse of the palace. Scabs are speedy excessively signifier over unfastened lesions sealing the entryway, like a row of soldiers barricading the manner. An enzyme called muramidase is found in cryings, mucose and the vaginal gap protecting the gaps from invasion. The mucous secretion of the nose traps microorganisms, forestalling them from go throughing farther and go forthing them stranded in the fosse. Any encroachers which do pull off to come in the tunnel, known as the respiratory piece of land, are rapidly brought to a arrest by the mucous secretion and the soldiers known as cilia, before being marched back out the palace the manner they entered. Any encroachers who do mouse through and make the tummy enter the Ce cavity of the palace, filled with acid, killing the encroachers.

If the invasion of the first line of defense mechanism is successful they are so met by the 2nd line of defense mechanism ; the guards stood on the walls of the palace. This is referred to as a non-specific response. These trade rapidly with the encroachers and the ground forces works in many different ways to see them off. The encroachers are targeted, caught and so marched along via the lymphatic system, to the blood watercourse, instead like being marched to the corporal ‘s office. Here the higher graded soldiers ; the white blood cells are in charge of covering with them. The regiment of white blood cells responsible for this are the scavenger cells, made from subdivisions ; neurophiles and monocytes. “ In this procedure, the white cell engulfs the pathogen, takes it into a vacuole inside the cytol and so digests it with lytic enzymes. ” ( Boyle et al, 1999, P.513 ) . Due to the short life span of these soldiers, they are merely capable of lasting for several yearss after killing the encroachers and so organize as Pus on the surface of the tegument.

The 3rd line of defense mechanism marks specific pathogens. This are dealt with by specializer soldiers who are capable of covering with specific immune responses. Lymphocytes are the major rank to cover with this onslaught. They are produced by the root cells of the bone marrow. When the ground forces gives them a call, they so leave the mill where they travel to the ground forces base to fix to be called upon to support the organic structure. There are two divisions based on their expertness ; T cells and B cells.

The T cells, travel to their army caput quarters in the Thymus. Merely a little sum of T cells reach the Thymus as the organic structure bound ‘s the measure to protect the organic structure from harm from self-engulfing. Here they mature and become equipped for the onslaught. “ The T cells are given T cell receptors, of which there are several types. The type of receptor received determines what type of T cell it will be, what its function is, and which cells it can interact with. ” ( Virtual Medical Centre, 2008 ) . The other division, the B cells mature in the bone marrow before going to the lymph and distributed to the lymph nodes ; the waiting room, where they wait until they are called upon.

B cells do non contend the encroacher straight, alternatively they are armed with arms, known as antibodies. The antibodies so travel in the blood to the site of infection. “ An antibody, or Ig, is a Y-shaped protein molecule that is made by a B lymph cell in response to a peculiar antigen. ” ( Boyle et al, 1999, P.515 ) . There are five different types of antibodies produced ; IgG, IgM, IgA, IgE and IgD. These are all Ig ‘s, they have a similar chief construction ; the Ig, but a variable terminal construction, leting the interaction to different antigens. These have assorted maps within the immune system and are capable of recognizing 1000000s of encroachers and bring forthing the relevant antibodies.

The antibody IgM is the largest antibody in size and distributed throughout the lymph and blood. This is the first type of antibody called in response to the infection, known as the primary response. Its construction is somewhat different to that of other Ig ‘s in that it is, “ five normal Ig ‘s joined at their bases. ” ( Virtual Medical Centre, 2008 ) . This allows its response to be so effectual.

When the particular antibody recognises the encroacher, it rapidly multiplies, organizing a ringer of plasma cells, which secrete a big sum of the specific antibodies. “ These receptors have the same form as the antibody that will be produced by the B cell. The antibody molecules are able to unite specifically with antigens. ” ( Indge et al, 2000, P.148 ) . Once the infection has been tackled, the bulk of the new B cells are no longer required and decease.

The antibody IgG is found in all bodily fluids and is the lone antibody which is capable to traverse the placenta during gestation, offering similar unsusceptibility to the fetus. “ Part of the IgG molecule is able to interact with tonss of cells of the immune system, and so it has the ability to excite a really direct onslaught on anything that it recognises. ” ( Virtual Medical Centre, 2008 ) . It is responsible for originating the secondary response.

The secondary response is much quicker. Some of the B cells after undertaking the infection, fail to decease and alternatively are given a new function within the ground forces as memory cells. This is of import as some encroachers, will try to come in the palace once more. To forestall farther infection and a besieging on the palace, these memory cells are rapidly called upon. “ These memory cells ‘remember ‘ what the pathogen is like and, if it tries to occupy once more, they all divide quickly to bring forth an even greater figure of active B cells. ” ( Boyle et al, 1999, P.515 ) . B cells are unable to transport out a response on their ain though, they require the aid of the T assistant cells.

T cells are besides specific in their function, merely recognizing specific encroachers as portion of a cell-mediated response. “ They compromise about 75 % of go arounding lymph cells. T cells are the predominant cell in the paracortical part of lymph nodes. ” ( GP Notebook, 2009 ) . There is a farther three divisions ; T killer cells, T assistant cells and T suppresser cells. When the encroachers are deep inside the palace, perforating the organic structure cells, these are desperately called upon. “ The cell surface membranes of T cells contain specific receptors with peculiar forms, similar to antibodies. However, these receptors do non recognize whole antigen molecules, unlike antibodies. ” ( Taylor et al, 1997, P. 487 ) .

“ Helper T cells are by far the most common T cell. They make up more than three quarters of the T cell population. ” ( Virtual Medical Centre, 2009 ) . These are responsible for commanding the immune response, instead like the ground forces general, giving orders to his soldiers. They instruct the B cells to split and bring forth antibodies, they instruct the other types of T cells to get down combat, and eventually name upon the macrophages to fix to steep the encroachers.

Killer T cells, besides known as cytotxic lymph cells, are the chief portion of the ground forces responsible for contending. Once instructions are received from the general T assistant cell, they begin their onslaught. They puncture holes in the cell wall of the encroacher, which finally consequences in the decease of the encroacher. “ The action of slayer T cells stimulates an addition in macrophage activity to unclutter up the dust. ” ( Aplastic Anaemia and Myelodysplasia Glossary, 2009 ) .

Suppressor T cells are like a go-between. “ When the immune response becomes inordinate, or when the infection has been dealt with successfully, these T cells damp down the immune response. ” ( Boyle et al, 1999, P.517 ) . This prevents unnecessary harm to the organic structure and a waste of resources.

Therefore the construction and administration of the immune system, is good developed into specific defense mechanisms, leting protection to the palace. If the first line is broken, the palace still has the protection of the 2nd and 3rd line of defense mechanism. It is merely after all three lines of defense mechanism have been broken, that the palace becomes wholly under besieging, ensuing in serious onslaught. This can be referred back to the organic structure, in that one time the different phases of the immune response fail, the organic structure is so unfastened to serious infection and diseases.


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BBC GCSE Bite size ( 2009 ) Pathogens [ on-line ] . Available from: hypertext transfer protocol: // # top [ Accessed 22nd November 2009 ]

Boyle, M. , Indge, B. , Senior, K. ( 1999 ) Human Biology. Collins. P.513, 515, 517.

GP Notebook ( 2009 ) T Cells [ online ] . Available from: hypertext transfer protocol: // ID=-194314206 [ Accessed 22nd November 2009 ]

Indge, B. , Rowland, M. , Baker, M. ( 2000 ) A New Introduction to Human Biology. Hodder & A ; Stoughton. P.148.

Taylor, D.J. , Green, N.P.O. , Stout, G.W. ( 1997 ) Biological Science 2 – Systems, Maintenance and Change. Cambridge. Soper. P.487.

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