Essay on Immune Disorders | Disorders | Human Health | Biology

Here is a compilation of essays on the ‘Immune Disorders’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Immune Disorders’ especially written for school and college students.

Essay on Immune Disorders

Essay Contents:

1. Essay on Hypersensitivity or Allergies
2. Essay on Autoimmunity
3. Essay on Immunodeficiencies

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Essay # 1. Hypersensitivity or Allergies: 

An allergy is the hypersensitivity of immune system of a person to some foreign substance, called allergen, which either comes in contact with or enters the body.

Type of Allergens:

The common allergens are dust, pollens, spores, feathers, fur, venom, food and drugs. Some physical agents also act as allergens.

Mechanism:

It involves three steps:

(a) Sensitisation:

In this, allergen acts as a mild antigen so stimulates the formation of antibodies which bind to mast cells of connective fissure. The antibodies produced are of Ig E type.

(b) Second Stimulation:

In this, allergens combine with antibody-bound mast cells which rupture and release histamine and serotonin.

(c) Histamine action causes hyper sensation.

Symptoms:

General symptoms of allergy are: inflammation of mucous membranes, sneezing, running eyes, irritations of throat and trachea, itching, skin rash etc.

Types:

(a) Hay Fever:

It is mainly due to pollens and spores of the plants. It is characterized by increased secretion of mucosa of nose, throat etc. and conjunctivitis.

(b) Asthma:

It is characterized by narrowing of bronchi, bronchiospasm and difficulty in breathing. Many asthma patients take aspirin or non-steroidal anti-inflammatory drugs (NSAID). Studies have shown that between 4 to 19% of asthmatic persons develop aspirin intolerance. NSAIDS are known to increase the risk of an asthma attack.

Most common allergen for asthma is house dust (containing faecal pellets of dust mites, animal dander and feathers); pollen grains of plants like congress grass; pet-animals; certain foods and drinks like eggs, fish, red wines, etc.; drugs like aspirin, pollutants like SO₂, CO₂ smoke, etc.

(c) Anaphylactic Shock:

It is a systemic allergic reaction affecting all the body tissues and may be due to some poisons like bee-sting, or some drugs like penicillin, or some food taken orally.

Prophylaxis:

The specific allergens should be identified and avoided. It can be diagnosed by tests like avoidance test, skin prick test, patch test etc.

Therapy:

The treatmeint of allergy by desensitisation is called immunotherapy. As allergy is mainly caused by histamine, so antihistamine pill gives relief by nullifying the histamine. Steroids, especially glucocorticoids, are also recommended against allergies but these have side effects. Main antihistamines are: Phenindamine, diphenhydramine and cyclizine etc.)

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Essay # 2. Autoimmunity:

It is a type of immune disorder when the immune system of an individual starts rejecting its own body cells or ‘self. This leads to a variety of diseases called autoimmune diseases. The type of disease depends upon the type of ‘self antigen’ involved.

The body cells acting as antigens or ‘non-self are called autoantigens e.g., if the autoantigens are R.B.Cs, then lymphocytes of immune system start destroying its own RBCs and causes chronic anaemia; if the self antigens are muscle cells, then immune system destroys own muscle cells and causes Myasthenia gravis characterized by severe weakness; and if the self antigens are liver cells, then chronic hepatitis occurs due to destruction of liver cells.

Other commonly occurring autoimmune diseases are insulin-dependent diabetes, multiple sclerosis (antibodies damage the myelin sheath of nerve cells), rheumatoid arthritis, Addison’s disease, Hoshimoto disease, ulcerative coitus, strep throat (damaged heart valves due to throat infection caused by streptococcal infection) and lupus erythmatosus.

Hoshimoto disease is also called autoimmune thyroiditis. In this, age factor or injury to thyroid gland causes hyposecretion of thyroxine. When thyroxine secretion falls below certain minimal limit, the antibodies are formed which destroy the thyroid gland.

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Essay # 3. Immunodeficiencies:

A number of diseases, some of which are inherited, are due to impaired immune responses. There may be a failure of antibody response (B-lymphocytes) or a failure of cellular immunity (T-lymphocytes) or a combination of both. These occur due to deficiency of B-cells and T-cells, especially in the children, so there are recurring bacterial or fungal infections e.g.,

(a) Severe Combined Immunodeficiency (SCID):

Is the most serious congenital immunodeficiency of children, so called primary immunodeficiency? In this, both B-cells and T-cells are absent. SCID is caused by a recessive gene mutation which causes deficiency of enzyme adenosine deaminase. So SCID is characterized by very low number of thymocytes. Such children are highly susceptible to various infections, so are kept alive in germ-free ‘isolation suits’.

(b) Acquired Immuno-Deficiency Syndrome (AIDS):

Cause:

AIDS is a severe viral disease which has been able to overcome all the defensive mechanisms of human body and generally leads to death. It is not a congenital disease but is an acquired disease, so called secondary immunodeficiency. It is a pandemic disease.

It is caused by a retrovirus-HIV (Human immuno­deficiency virus) as enclose single-stranded RNA genome (Fig. 8.25), earlier called LAV (Lymphadenopathy associated virus) or HTLV (Human T-lymphotrophic virus). It was first reported in African green monkey but was first isolated in man by Montagnier et. al. (1983) and Gallo et. al. (1984).

So far, nine sub-types of HIV-I and four sub-types of HIV-2 have been isolated. In India, HIV-I sub-the C has been found primarily responsible for heterosexual transmission. (3ther strains found in India so far are sub type A, B and E. In India, HTV-IB is found primarily in drug users.

Historical Background:

It was first recognised in Hatai (U.S.A.) in 1981. In India, AIDS-virus was first reported in 1986 among ten prostitutes in Chennai.

Incidence of AIDS in World:

According to WHO—1990 report, there were about 8 million people infected with HIV, of which over one-third were women. By the end of 1995, the number of HIV-positive persons over worldwide was about 25 million adults and 1.5 million children. By July 2004, there were about 38 million people living with HIV/AIDS and since 1980s, this pandemic disease has caused about 20 million deaths.

More than 8,500 children become infected with HIV every day i.e., six children every minute. More than 90% of them are born to an HIV-positive mother and acquire the virus before or during birth or through breast feeding. On an average, 16,000 people become infected with HIV everyday – or 11 persons a minute, 90 per cent of them being in the developing countries. Upto end of 2011, HIV has caused deaths of over 25 million people since 1981. In 2002, AIDS became the primary cause of mortality.

Incidence of AIDS in India:

In India, AIDS-virus was first reported in 1986 among prostitutes in Chennai. Upto 1992, about 104 full blown AIDS cases (Number of full blown cases of AIDS has increased to 5000 upto October 31, 1997) had been detected in India. WHO in association with NACO (National AIDS Control Organization) reported that at 1999 end, there were about 3.5 million HIV-positive persons in India, 50% of which fall in the age group of 15-24 years of age.

According to UN AIDS report (July 2000), HIV population in India was as high as 4.1 million (with second highest HIV population in the world after South Africa). In India, AIDS infection is rising at the rate of 10 per 1,000 persons (about 1%). HTV-positivity in India has increased from 2.5 persons per thousand in 1986 to 17 persons per thousand in 1996. Now it is no longer restricted to truck-drivers, commercial sex- workers or intravenous drug users but it has crossed all social and economic barriers. So India is now called the “World Capital of AIDS”.

About 0.5 per cent of Indian population is affected with HIV/AIDS and the six states with high incidence of HIV/AIDS cases are: Tamil Nadu, Maharashtra, Andhra Pradesh, Karnataka, Nagaland and Manipur. Pattern of disease is very alarming in Manipur where 43.7% intravenous drug users were found HIV positive. In sex-workers of Mumbai, HIV – positivity has increased from 1.66 per cent in 1988 to 42 per cent in 1992.

Theme of AIDS day December 1, 2004: Women, Girls, HIV & AIDS — Have you heard me today?

An estimated 5.1 million people of India are infected with HIV. Out of the reported full blown AIDS cases, about 75% of the infections are in the male population, 85% of which are through sexual route of transmission.

Main causes of this high rate of increase of AIDS- incidence in India are:

Alarming extent of ignorance and prejudice about the disease, false view of its being contagious, reluctance of medical professionals to treat the disease; medical confidentiality, sexual behaviour, inadequate screening facilities; inadequate funding, low female literacy rate, etc. India is supposed to be the next “hot spot for the greatest ballooning of HIV infection” as it has certain population groups (e.g. sex workers and truck-drivers) which can spread it at an alarming rate.

Mechanism of Action of HIV Virus (Fig. 8.26):

When HIV attacks helper-T cell, (T_H), then the virus binds CD-4 receptor present on the surface of the host cell by its GP-120 protein. CD-4 acts as a gateway for the entry of virus. Viral genomic RNA and enzyme reverse transcriptase enter inside the host cell while its protein coat remains outside. The viral RNA synthesizes DNA in the presence of enzyme reverse transcriptase and is called reverse transcription.

The DNA copy of HIV is incorporated into host’s DNA to form a prophase and replicates along with host’s DNA. The viral genome transcribes large number of RNA particles, each of which gets surrounded by a portentous capsid to complete viral particles. Finally the infected host cell is lysed and many HIV viruses are released which infect new Helper- T cells. So the process is repeated which causes a progressive decrease in the number of helper-T cells.

Modes of Transmission:

AIDS is not a contagious disease. It does not spread through contact; caring of infected persons; sharing meals; mosquito-bite, light- kissing, handshake, blood-sucking insects, etc. Main sources of epidemiology of HIV are—sexual intercourse, use of contaminated hypodermic needles and syringes by intravenous drug abusers; contaminated blood transfusion, organ transplantation, artificial insemination; from infected mother to baby during parturition (30% chances) and breast feeding.

Diagnosis:

AIDS can be diagnosed by ELISA test (Enzyme-Linked Immuno-sorbent Assay) and Western Blot test. These tests give results only 2 to 24 weeks after the HIV-infection as no antibodies are formed during this “window period”. Other tests for diagnosis of AIDS are: Rapid tests like Dot Blot and Latex Agglutination Tests and simple tests like Particle Agglutination Tests. The ELISA test is based on antigen- antibody and enzyme-substrate reactions.

Incubation Period:

It ranges between 5-10 years. Average incubation period is of 28 months.

Symptoms:

HIV attacks Helper T-lymphocytes. The reduction in number of Helper T-lymphocytes causes severe cellular immuno-deficiency. Number of T-cells drops to even below 200 in comparison to 500-1500 in a normal person. So it is a disorder of cell-mediated immune system of the body. So the person becomes highly susceptible to bacteria (especially to Mycobacterial strains), viruses, fungi and parasites like Toxoplasma. These clinically unhealthy persons are called opportunistics.

AIDS is characterized by a group of symptoms:

Psychosis or chronic encephalitis—severe brain damage.

Thrombocytopenic purpurea—decreased count of blood platelets causing haemorrhage.

Lymphoma—cancer of lymphatics.

Lymphadenopathy—swelling of lymph nodes.

Another peculiar Symptom of AIDS is severe wasting syndrome (substantial weight loss and general decline in health).

AIDS patients also become more susceptible to infections of any system of body. When brain is damaged, then it may cause loss of memory, ability to speak and even think. A full blown AIDS patient dies within three years and mortality is 100%.

Most serious form of AIDS is AIDS-related complex (ARC) which is characterized by swollen lymph-nodes, fever, night sweats and loss of weight.

High Risk Groups:

These include the multiple sexual partners; homosexuals; university and college students; intravenous drug addicts; haemophillics; recipients of transfused blood and blood products; heterosexual sex partners; truck drivers; etc.

Prophylaxis (Preventive Measures):

No absolutely satisfactory vaccine is yet available against HIV infection of Indian types, so management of AIDS depends only on preventive measures like educating the people especially of high risk-groups; use of disposable needles and syringes; screening tests for donors of blood, organs, semen and growth hormones; having mutually faithful, monogamous relationship and avoiding prostitution, multi-partner sex and homosexuality; using condoms.

The lifelong monogamy and use of disposable syringe are best ways to prevent the spread of AIDS. In India, NACO and many Non-Government Organisations (NGOs) are doing their best efforts to educate people about AIDS. Main aim of these awareness campaigns is not to allow the people to die of ignorance.

India started a National AIDS Control Programme in 1987 which involved a three-way attack: surveillance, health and community education and promotion of safety of blood and blood products. Every year, December 1 is recalled as World AIDS Day.

Therapy:

Till today there is no specific therapy against HIV infection although Azidothymidine (AZT) (but has side effects like anaemia) has been found to suppress AIDS virus and TIAS injection (prevents proliferation of AIDS virus). Efforts are on for a vaccine against the virus which is urgently needed to stem the tide of HIV.

Though about 43 vaccines have been developed in USA and many are in various stages of testing but none has shown very encouraging results. However, these vaccines may not be appropriate for the Indian strains. So there is need of giving top priority to develop a vaccine for preventing HIV-infection.

Two way strategy is suggested:

(i) Anti-Retroviral Therapy (ART) against HIV. Since 1996, Highly active anti-retroviral therapy (HAART) based on protease inhibitor is available. Though it helps in stabilization of the symptoms of AIDS patients but does not provide cure from the virus nor from the symptoms of AIDS.

(ii) Immunostimulative Therapy to increase the number of resistance providing cells.