Immunity, Vaccines, Cancer and AIDS

How the body defends itself, and important disease conditions related to immunity.

Immunity, Vaccines, Cancer and AIDS

The human body is continuously exposed to microorganisms and other foreign substances. The body has several defence mechanisms that protect it from disease-causing organisms. These defence mechanisms together form the basis of immunity.

इसके साथ-साथ vaccination शरीर को specific pathogens के विरुद्ध पहले से तैयार करने में मदद करता है। Cancer में cells की uncontrolled growth होती है, जबकि AIDS में HIV के कारण immune system कमजोर हो जाता है।

1. Immunity

Immunity is the ability of the body to resist or fight against disease-causing organisms and harmful foreign substances.

मानव शरीर में immunity केवल एक प्रकार की defence नहीं है। इसमें कई organs, cells और molecules मिलकर काम करते हैं।

Types of Immunity

Immunity is broadly classified into:

  • Innate immunity
  • Acquired immunity

2. Innate Immunity

Innate immunity is the immunity that is present from birth. It provides the first line of defence against pathogens.

यह immunity किसी particular pathogen के लिए specifically developed नहीं होती। इसलिए इसे non-specific defence भी कहा जाता है।

Four Major Barriers of Innate Immunity

Barrier Examples Function
Physical barriers Skin, mucus-coated epithelium Prevent entry of pathogens
Physiological barriers HCl in stomach, saliva, tears Destroy or inhibit pathogens
Cellular barriers Neutrophils, monocytes, macrophages, natural killer cells Destroy pathogens or infected cells
Cytokine barriers Interferons Protect cells against viral infection

Example

When a pathogen tries to enter through the skin, the skin acts as a physical barrier. If pathogens enter the body, phagocytic cells can engulf and destroy them.

3. Acquired Immunity

Acquired immunity develops during an individual's lifetime after exposure to specific pathogens or their antigens.

यह immunity specific होती है। इसका सबसे important feature है immunological memory.

जब शरीर पहली बार किसी pathogen के antigen का सामना करता है, तो primary immune response develop होता है। उसी antigen से दूसरी बार exposure होने पर response अधिक तेज और मजबूत हो सकता है। इसे secondary immune response कहते हैं।

Major Features of Acquired Immunity

  • Specificity
  • Memory
  • Ability to distinguish self and non-self

4. B-Lymphocytes and T-Lymphocytes

Acquired immunity mainly involves B-lymphocytes and T-lymphocytes.

B-Lymphocytes

B-lymphocytes are mainly responsible for antibody-mediated immune response.

जब B-cells activate होते हैं, वे antibodies produce करने वाली plasma cells में differentiate कर सकते हैं।

T-Lymphocytes

T-lymphocytes are involved in cell-mediated immunity.

कुछ T-cells infected cells को destroy करने में मदद करते हैं, जबकि helper T-cells अन्य immune cells को coordinate और activate करने में important role निभाते हैं।

5. Antibodies

Antibodies are specialised proteins produced by B-lymphocytes in response to specific antigens.

Antibody और antigen के बीच specific interaction होता है। इसे ऐसे समझ सकते हैं कि antibody का binding region particular antigen को पहचानने के लिए suited होता है।

Antibodies are commonly represented as Y-shaped molecules.

Important Immunoglobulins

Immunoglobulin Important association
IgG Major antibody in blood and extracellular fluid
IgA Important in secretions such as saliva, tears and mucosal secretions
IgM Important in primary immune response
IgE Associated with allergic responses
IgD Present mainly on the surface of B-lymphocytes

6. Active and Passive Immunity

Active Immunity

Active immunity develops when the person's own immune system produces antibodies and immune memory after exposure to an antigen.

It may develop naturally after infection or artificially through vaccination.

Passive Immunity

Passive immunity occurs when ready-made antibodies are transferred to an individual.

इसमें antibodies शरीर के बाहर या किसी दूसरे source से प्राप्त होती हैं। इसलिए immune memory generally develop नहीं होती।

Examples

  • Maternal antibodies transferred to the foetus through the placenta → Passive immunity
  • Antibodies present in mother's milk, especially colostrum → Passive protection
  • Antibody-containing preparations given after certain exposures → Artificial passive immunity
Active Immunity Passive Immunity
Body produces its own antibodies. Ready-made antibodies are received.
Usually develops more slowly. Provides immediate protection.
Memory cells can develop. Usually no long-lasting immune memory.
Example: Vaccination Example: Maternal antibodies

7. Vaccines and Vaccination

A vaccine contains antigenic material that stimulates the immune system to develop protection against a particular disease.

Vaccination is the process of administering a vaccine to induce protective immunity.

Vaccination allows the immune system to develop immunological memory without requiring the person to experience the full disease.

How Does Vaccination Work?

  1. A vaccine introduces antigenic material into the body.
  2. The immune system recognises the antigen as foreign.
  3. Specific immune cells become activated.
  4. Antibodies and memory cells are produced.
  5. On later exposure to the same pathogen or antigen, the immune response can be faster and stronger.

इसका मुख्य advantage यह है कि immune system पहले से prepared रहता है।

8. Allergy

Allergy is an exaggerated or inappropriate immune response to normally harmless substances called allergens.

Common allergens include dust, pollen, certain foods and animal dander.

Allergic reactions are commonly associated with IgE antibodies and the release of chemicals such as histamine from mast cells.

Common Symptoms of Allergy

  • Sneezing
  • Watery eyes
  • Runny nose
  • Skin rashes
  • Breathing difficulty in severe reactions

9. Autoimmunity

Autoimmunity occurs when the immune system mistakenly reacts against the body's own cells or tissues.

अर्थात् immune system self और non-self को सही तरीके से distinguish नहीं कर पाता और body के own tissues को target करने लगता है।

Example: Rheumatoid arthritis is an autoimmune disorder.

10. Cancer

Cancer is a group of diseases characterised by uncontrolled and abnormal growth of cells.

Normally, cell division is carefully regulated. Cancer develops when this regulation is disrupted and abnormal cells continue to divide.

11. How Does Cancer Develop?

Normal cells follow mechanisms that control cell growth and division. Genetic changes can disturb these controls.

Such changes may activate growth-promoting genes or impair genes responsible for controlling cell division and cell death.

Resulting abnormal cells may continue to multiply and form a mass called a tumour.

12. Benign and Malignant Tumours

Benign Tumour Malignant Tumour
Usually remains localised. Can invade surrounding tissues.
Generally does not invade distant tissues. Can spread to distant organs.
Usually less dangerous. Potentially life-threatening.

13. Metastasis

Metastasis is the spread of malignant cancer cells from the original site to other parts of the body.

Malignant cells can enter the blood or lymphatic system and reach distant organs, where they may form secondary tumours.

Important: Tumour cells spreading from one part of the body to another is called metastasis.

14. Causes of Cancer

Cancer can result from genetic changes caused by several factors.

  • Carcinogenic chemicals
  • Ionising radiation
  • Some viruses
  • Certain lifestyle-related factors
  • Inherited genetic changes in some cases

Substances or agents capable of causing cancer are called carcinogens.

15. Cancer-Causing Viruses

Some viruses can contribute to the development of cancer. Such viruses are called oncogenic viruses.

Viral infection may alter cellular genes and disturb normal control of cell growth.

16. Detection and Diagnosis of Cancer

Early detection is important because treatment can be more effective when cancer is identified at an earlier stage.

Important methods used in cancer diagnosis include:

  • Biopsy
  • Histopathological examination
  • Imaging techniques
  • Blood and other laboratory tests
  • Molecular and genetic tests in appropriate cases

Biopsy

In a biopsy, a small sample of tissue is removed and examined to determine whether abnormal or cancerous cells are present.

17. Treatment of Cancer

Treatment depends on the type and stage of cancer.

Surgery

Surgery involves removal of the tumour or affected tissue when appropriate.

Radiotherapy

Radiotherapy uses high-energy radiation to damage and destroy cancer cells.

Chemotherapy

Chemotherapy uses anti-cancer drugs to destroy or inhibit rapidly dividing cancer cells.

Immunotherapy

Immunotherapy uses or stimulates components of the immune system to help recognise and attack cancer cells.

Modern cancer treatment may involve a combination of surgery, radiotherapy, chemotherapy, targeted therapies and immunotherapy depending on the case.

18. AIDS

AIDS stands for Acquired Immuno Deficiency Syndrome.

It is caused by the Human Immunodeficiency Virus (HIV).

HIV mainly affects cells of the immune system, especially helper T-lymphocytes, and progressively weakens immune defence.

19. Transmission of HIV

HIV can be transmitted through:

  • Unprotected sexual contact with an infected person
  • Transfusion of infected blood
  • Sharing contaminated needles or syringes
  • Transmission from infected mother to child during pregnancy, childbirth or breastfeeding

HIV is not transmitted by ordinary casual contact such as shaking hands, hugging, sharing food or sitting beside an infected person.

20. HIV and the Immune System

After entering the body, HIV infects immune cells. The virus uses the machinery of host cells to multiply.

Over time, the number and functioning of helper T-lymphocytes may decrease significantly.

As immune function becomes weaker, the person becomes increasingly vulnerable to opportunistic infections and certain cancers.

21. Diagnosis of AIDS/HIV Infection

HIV infection can be detected using specific laboratory tests. Antibody-based tests such as ELISA have been widely used for screening, followed by appropriate confirmatory testing.

22. Prevention of AIDS

  • Practise safe sexual behaviour.
  • Use sterile needles and syringes.
  • Ensure proper screening of blood before transfusion.
  • Avoid sharing needles or syringes.
  • Follow appropriate medical precautions during pregnancy and childbirth.

Important Comparison

Topic Key Point
Innate immunity Present from birth; non-specific
Acquired immunity Specific and develops during life
Active immunity Body produces its own immune response
Passive immunity Ready-made antibodies are received
Vaccine Stimulates specific immune protection and memory
Cancer Uncontrolled abnormal cell growth
Metastasis Spread of malignant cells to distant sites
AIDS Caused by HIV; weakens immune system

Board-Oriented Very Short Questions

  1. What is immunity?
  2. What is innate immunity?
  3. What is acquired immunity?
  4. Name the four major barriers of innate immunity.
  5. What are antibodies?
  6. Which cells produce antibodies?
  7. What is immunological memory?
  8. What is active immunity?
  9. What is passive immunity?
  10. What is vaccination?
  11. What is an allergen?
  12. Which immunoglobulin is mainly associated with allergy?
  13. What is autoimmunity?
  14. What is cancer?
  15. What is a tumour?
  16. Differentiate between benign and malignant tumours.
  17. What is metastasis?
  18. What are carcinogens?
  19. What is biopsy?
  20. Name two methods used in cancer treatment.
  21. What is the full form of AIDS?
  22. What is the full form of HIV?
  23. Which cells are mainly affected by HIV?
  24. Name one test used for HIV screening.

Short Answer Practice

  1. Explain innate immunity with its major barriers.
  2. Explain acquired immunity and immunological memory.
  3. Differentiate between active and passive immunity.
  4. Explain the role of B-lymphocytes and T-lymphocytes in immunity.
  5. How does vaccination provide protection against disease?
  6. What is allergy? Explain the role of IgE and histamine.
  7. What is autoimmunity? Give one example.
  8. What is cancer? Explain how uncontrolled cell division can lead to tumour formation.
  9. Differentiate between benign and malignant tumours.
  10. What is metastasis?
  11. Explain the major methods used for cancer treatment.
  12. Explain how HIV weakens the immune system.
  13. Describe the major modes of transmission and prevention of HIV infection.

Long Answer Practice

  1. Describe innate and acquired immunity with suitable examples.
  2. Explain active and passive immunity and give suitable examples of each.
  3. Explain vaccination, its mechanism and importance in disease prevention.
  4. Describe cancer, its causes, detection and major methods of treatment.
  5. Explain AIDS with reference to its causative agent, transmission, effect on the immune system and prevention.

Multiple Choice Questions

  1. Immunity present from birth is called:
    (A) Acquired immunity
    (B) Innate immunity
    (C) Artificial immunity
    (D) Passive immunity
    Answer: (B) Innate immunity
    2. ```
  2. Antibodies are mainly produced by:
    (A) B-lymphocytes
    (B) Red blood cells
    (C) Platelets
    (D) Neurons
    Answer: (A) B-lymphocytes
  3. Which immunoglobulin is associated with allergic reactions?
    (A) IgA
    (B) IgE
    (C) IgG
    (D) IgM
    Answer: (B) IgE
  4. Vaccination mainly produces:
    (A) Immunological memory
    (B) Cancer cells
    (C) Pathogens
    (D) Allergens
    Answer: (A) Immunological memory
  5. Ready-made antibodies are received in:
    (A) Active immunity
    (B) Passive immunity
    (C) Innate immunity only
    (D) Autoimmunity
    Answer: (B) Passive immunity
  6. Uncontrolled division of abnormal cells is characteristic of:
    (A) Cancer
    (B) Allergy
    (C) Vaccination
    (D) Immunity
    Answer: (A) Cancer
  7. Spread of malignant cells to distant organs is called:
    (A) Mutation
    (B) Metastasis
    (C) Vaccination
    (D) Phagocytosis
    Answer: (B) Metastasis
  8. AIDS is caused by:
    (A) HBV
    (B) HIV
    (C) Plasmodium
    (D) Salmonella
    Answer: (B) HIV
  9. HIV mainly affects:
    (A) Helper T-lymphocytes
    (B) Red blood cells
    (C) Platelets
    (D) Bone cells
    Answer: (A) Helper T-lymphocytes
  10. A small tissue sample examined for cancer diagnosis is obtained by:
    (A) Vaccination
    (B) Biopsy
    (C) Transfusion
    (D) Dialysis
    Answer: (B) Biopsy
  11. Which of the following is a physical barrier of innate immunity?
    (A) Skin
    (B) Antibody
    (C) Memory cell
    (D) Vaccine
    Answer: (A) Skin
  12. Which treatment uses high-energy radiation to destroy cancer cells?
    (A) Chemotherapy
    (B) Radiotherapy
    (C) Vaccination
    (D) Immunisation
    Answer: (B) Radiotherapy
    13. ```

Fill in the Blanks

  1. Immunity present from birth is called ______ immunity.
  2. Specific immunity developed during life is called ______ immunity.
  3. Antibodies are mainly produced by ______-lymphocytes.
  4. Cell-mediated immunity mainly involves ______-lymphocytes.
  5. Vaccination produces ______ memory.
  6. Ready-made antibodies provide ______ immunity.
  7. An exaggerated immune response to harmless substances is called ______.
  8. The spread of malignant cells to distant organs is called ______.
  9. Agents capable of causing cancer are called ______.
  10. AIDS is caused by ______.

Answers: innate, acquired, B, T, immunological, passive, allergy, metastasis, carcinogens, HIV

Assertion and Reason Practice

  1. Assertion: Vaccination can provide long-term protection against specific diseases.
    Reason: Vaccination can stimulate the formation of immunological memory.
    Answer: Both Assertion and Reason are correct, and the Reason correctly explains the Assertion.
    2. ```
  2. Assertion: Passive immunity generally does not produce long-lasting immune memory.
    Reason: Passive immunity involves the transfer of ready-made antibodies.
    Answer: Both Assertion and Reason are correct, and the Reason correctly explains the Assertion.
  3. Assertion: Malignant tumours can be more dangerous than benign tumours.
    Reason: Malignant cells can invade tissues and metastasise to distant organs.
    Answer: Both Assertion and Reason are correct, and the Reason correctly explains the Assertion.
  4. Assertion: HIV infection can increase susceptibility to opportunistic infections.
    Reason: HIV progressively damages important components of the immune system.
    Answer: Both Assertion and Reason are correct, and the Reason correctly explains the Assertion.
    5. ```

Quick Revision

  • Innate immunity → Present from birth → Non-specific defence
  • Acquired immunity → Specific → Immunological memory
  • B-cells → Antibody-mediated immunity
  • T-cells → Cell-mediated immunity
  • Vaccine → Antigenic stimulation → Immune memory
  • Passive immunity → Ready-made antibodies
  • Allergy → Exaggerated immune response → IgE
  • Cancer → Uncontrolled abnormal cell growth
  • Metastasis → Spread of malignant cells
  • AIDS → HIV → Immune system impairment

Key Terms

Term Meaning
Antigen A foreign substance that can trigger a specific immune response
Antibody Specific protein produced by B-cell-derived plasma cells
Immunity Ability of the body to resist disease-causing agents
Vaccine Antigenic preparation used to stimulate protective immunity
Allergen Substance that triggers an allergic response
Carcinogen Agent capable of causing cancer
Metastasis Spread of malignant cells to distant sites
HIV Human Immunodeficiency Virus
AIDS Acquired Immuno Deficiency Syndrome
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