Immune System

“Disease” is a very wide term. Any change from the normal state that causes discomfort or disability or impairs the health may be called a disease. The oxford English Dictionary defines disease as “a condition of the body or some part or organ of the body in which its functions are disturbed or deranged”.  A person free of disease is often said to be healthy. This is not fully true. The term “Health” has a very wide scope. The World Health Organization (WHO) gave the following definition of health in 1948


The diseases may be broadly classified into two types : Congenital and acquired.

(i) Congenital Diseases : These are anatomical or physiological abnormalities present from birth. They may be caused by (i) a single gene mutation (alkaptonuria, phenylketonuria, albinism, sickle-cell anaemia, haemophilia, colour blindness); (ii) chromosomal aberrations (Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome); or (iii) environmental factors (cleft palate, harelip). Unlike the gene-and chromosome-induced congenital defects, environmentally caused abnormalities are not transmitted to the children.

(ii) Acquired Diseases : These diseases develop after birth. They are further of two types : communicable and non-communicable.

(a) Communicable (Infectious) Diseases : These diseases are caused by viruses, rickettsias, bacteria, fungi, protozoans and worms.

(b) Noncommunicable (Noninfectious) Diseases : These diseases remain confined to the person who develops them and do not spread to others.

                                                              VIRUS COMMUNICABLE DISEASES

                                                                         Bacterial diseases and their pathogens


Causative Bacterium

  1. Cholera

  2. Pneumonia

  3. Typhoid

  4. Tetanus

  5. Diphtheria

  6. Whooping cough

  7. Tuberculosis

  8. Plague

  9. Leprosy

  10. Syphilis

  11. Gonorrhoea

  12. Diarrhoeal Diseases

  13. Anthrax

Vibrio comma (Vibrio cholerae)

Diplococcus pneumoniae

Salmonella typhi

Clostridium tetani

Corynebacterium diphtheriae

Bordetella pertussis

Mycobacterium tuberculosis

Pasteurella pestis

Mycobacterium leprae

Treponema pallidium

Neisseria gonorrhoeae

Escherichia coli, Shigella dysenteriae, Campylobacter, Salmonella

Bacillus anthracis


                                                                   Sexually Transmitted Diseases (STD) in Human


Causative organism

Nature of Disease

Symptoms – Treatment

(1)AIDS (Acquired Immuno deficiency Syndrome)

Retrovirus – HIV


Enlarged lymph nodes, long fever, weight loss – Nil

(2)Genital Herpes

Herpes simplex virus


Painful ulcer on genitals – Nil

(3)Genital warts

Human papilloma virus (HPVs)


Tumor of the vulva, vagina, anus and penis – Nil


Neisseria gonoerrheae


Infection of all genital organs or PID – Penicillin


Chlamydia trachomatis


White patches on vagina or PID – Nystatin


Treponema pallidum


Cancer and skin eruption – Benzene and Penicillin


Trichomonas vaginalis


Greenish-yellow vaginal discharge–Metronidazole.


Haemophilus ducreyi


Foul discharge and ulcer Drug : Sulphonamide

(9)Lymphogranuloma venerum

Lymphogranuloma psittacosis bacteria


Inguinal lymphadenopathy Drug : Tetracycline

Common name

Zoological name

Causative organism



Anopheles sps

Culicine sps

Stegomyia sps

Aedes aegypti


Wuchereria bancrofti

Flavovirus fibricus

Dengue virus


Rat flea

Xenopsilla cheopsis

Xenopsilla sps

Pasteurella pestis

R. typhi

Bubonic plague

Endemic typhus


Musca sps

  1. Shigella sps

  2. Salmonella typhi

  3. Salmonella paratyphi

  4. Hepatitis type – A virus

Bacillary dysentery

Typhoid fever

Paratyphoid fever

Infectious hepatitis

Sand fly

Phlebotomus papatasi



Leishmania donovani

Sand fly fever

Kala azar

Body louse


Rickettsia prowazeki

R. Quintana

Trench fever


Trombicula akamushi

R. Tsutsugamushi

Scrub typhus (Tsutsugamushi fever)

Itch mite

Sarcoptes scabieri


Tick fever,

Amblyomma sps

R. rickettsiae

Rocky mountain spotted theileriosis

House fly

Musca domestica

Vibrio cholerae



Infantile diarrhoea

Bed bug


Relapsing fever

Tse-tse fly

Glossina palpalis

Trypanosoma gambiense

Sleeping sickness

                                                                        Important Helminth Diseases in Humans




Mode of Infection

Taeniasis & Cysticercosis

Taenia solium – the pork tapeworm


By taking raw or undercooked measly pork


Ascaris lumbricoides

Small intestine

By taking eggs with food and water




bancrofti – the flarial worm

Lymphatics and connective tissue

By bites of Culex mosquitoes

Ancylostomiasis (Hookworm disease)

Ancylostoma duodenale – the hookworm

Small intestine

By boring through the skin, usually of feet.


System of body which prevent the body fromdiseases and cancer is calledimmune system.
(L. immunis – freedom/exempt).


  • Resistance of the body against a pathogen or disease. Immunity is the ability of an individual to resist against diseases and allergy.

  • Immune system protects body from various pathogens/infectious agents/ allergens and cancer.

  • Immunology is the science of development of immunity against particular pathogen / allergens.


Immunity is of two types –

(1)Congenital immunity or innate Immunity or Non-specific immunity.

(2)Acquired immunity or Adaptive or specific immunity.


It ispresent by birth in most of animals and forms natural defence system which is always available to protect the body against various types of antigens. It is also callednative immunity.


  • This immunity isacquired after birth due to previous infection, vaccination or inoculation of antiserum. It occurs only in vertebrates.

  • It supplements protection provided by innate immunity. This immunity recogniseas and selectively eliminate the pathogen.

  • It has four unique features –


·Acquired immunity is specific for specific micro-organisms.

It is the ability to differentiate various foreign molecules.


·This system recognise the vast variety of micro-organisms.

(iii)Discrimination between self and non-self

·It can recognise self (body or tissue) and non self (foreign tissue) and respond according to them.


·When a pathogen enter inside the body, body takes longer times to recoganise and respond to it, this is calledprimary immune response but the memory of this encounter remains in immune system.

·When this pathogen enters second time inside the body, body immune system rapidly recognises this pathogen and responds quickly to it. This is calledsecondary immune response. This is based on memory of immune system.


It is of two types – (1) Passive acquired immunity (2) Active acquired immunity.

(1)Active Immunity : When an organism’s own cells produce antibodies it is called active immunity. It develops when a person suffers from a disease or gets vaccination for a disease.

(2)Passive Immunity : In passive immunity, the antibodies are produced in some other organisms (e.g. vertebrates) in response to the given antigen. These antibodies are then injected into the human body at the time of need. This is known asinoculation. For example persons infected by rabies, tetanus, Salmonella (causes food poisoning) and snake venom are given the sufficient amount of antibodies so that they can survive.

                           Difference between Active Immunity and Passive Immunity

Active Immunity

Passive Immunity

(1)It is developed when the person’s own cells produce antibodies in response to infection or vaccine.

(1)It is develop when antibodies produced in other organisms are injected into a person to counter act antigen such as snake venom,

(2)It provides relief only after long period.

(2)It provides immediate relief.

(3)It has no side effects.

(3)It may cause reaction.

(4)It is long lasting.

(4)It is not long lasting.

                                                              Autoimmune Disorders



Antibodies Against


Lower back pain

Kidney cell antigens that resemble Strep bacteria antigens

Grave disease

Restilessness,Weight loss,irritability,

Increased heart rate  and Blood pressure

Thyroid gland antigens near thyroid stimulating hormone receptor, causing overactivity

Juvenile diabetes

Thirst, hunger, weakness, emaciation

Pancreatic beta cells

Hemolytic anemia

Fatigue and weakness

Red blood cells

Myasthenia gravis

Muscle weakness

Receptors for nerve messages on skeletal muscle

Pernicious anemia

Fatigue and weakness

Binding site for vitamin B on cells lining stomach

Rheumatic fever

Weakness, shortness of breath

Heart cell antigens that resemble Strep bacteria antigens

Rheumatoid arthritis

Joint pain and deformity

Cells lining joints


Thick, hard, pigmented skin patches

Connective tissue cells

Systemaic lupus erythamtosus

Red rash on face, prolonged fever, weakness, kidney damage

DNA, neurons, blood cells

Ulcerative colitis

Lower abdominal pain

Colon cells

                                                           Cells of Immune System


Cell Type



Helper T Cell

Assists the immune process by helping other cells in the immune system to achieve an efficient immune response.


Cytotoxic T Cell

Detects and kills infected body cells recruited by helper T cells.


Suppressor T Cell

Guards against the overproduction of antibodies and overactivity of cytotoxic T cells.


Memory cell

“Remembers” the original stimulation by the immune system and remains in the lymphoid tissue.


Natural killer cell (NK)

The lymphocyte without receptor site and help to attack and neutralize virus-infected and tumor cells.


B Cell

Precursor of plasma cell, specialized to recognize a specific foreign antigen.


Plasma cell

Biochemical factory devoted to the production of antibodies directed against a specific antigen.


Mast cell

Initiator of the inflammatory response which aids the arrival of leucocytes at a site of infection, secretes histamine and is important in allergic response.



Precursor of macrophage.



The body’s first cellular line of defence; also serves as antigen presenting cell to B and T cells and engulfs antibody covered cells.

                                                                                      Some Important Vaccines

Name of Vaccine

Category of Vaccine

Used for treatment of


Live vaccine (actual weakened germs)


(2)Cholera Vaccine

Killed vaccines (micro-organisms are killed)


(3)Mumps Vaccine (MMR)

Live vaccine (actual weakened germs)

Mumps Measles & Rubella

(4)Oral Polio Vaccine (OPV)

Live vaccine

Polio, 1st does given when child is 3 months old. Booster does is given after 1 year

(5)Rubella Vaccine

Live vaccine

German measles and small pox

(6)Rubeolla Vaccine

Live vaccine


(7)Tetanustoxoid (TT)

Toxoid (bacterial toxin looses toxicity but retains antigenicity)


(8)Toxoid Serum

Toxoid (bacterial toxin looses toxicity but retains antigenicity)


(9)Typhoid Vaccine (TAB)

Killed vaccine (micro organisms are killed)

Typhoid (Typhoid & Paratyphoid)

(10) Triple Antigen (DPT)

(Diphtheria, Pertussis Tetanus)


Diphtheria, tetanus and whooping cough, Ist dose given when child is 3 months old. Booster dose at 2 years.

  • Alesis Carr : Proposed “Principle of Histocompatibility”.

  • Two types of antigens involved in rejection of organ transplantation :

    • Major Histocompatible complex antigens (Human Leucocyte Antigens) : Present on the surface of the cells of transplanted organs.

    • Minor histocompatible antigens.   

  • Immuno suppressants : Drugs used to suppress the immune system to avoid the rejection of organ transplantation.

  • Sibling species : Individuals have more or less similar genetic constitution.

  • Dr. Gait inventor : Developed the technique of tissue engineering.

  • Dermograft : It involves human skin graft. It is first achievement in the field of tissue engineering and may lead a new era in the field of transplant surgery. In this, stem cells are taken from the foreskin of newly circumcised body and then grown on a biodegradable mesh.

  • Colostrum : First milk secreted from the mammary glands after birth of baby.

  • Anamnestic response : Elevated immune response caused by memory cells to an antigen exposed for the second time.

  • Antiserum : Serum containing antibodies against a specific antigen.

  • Autograft : Transplantation of tissue from one part of body to another part of same individual.

  • Homograft or Allograft : A graft derived from a genetically dissimilar individual of same species.

  • Heterograft or Xenograft : A grafted between organisms of different species.

  • Hepatitis-A is also known as infectious hepatitis and is caused by HAV.

  • Hepatitis-D is caused byHepatitis-D Virus (HDV).

  • Viricides : Virus- killing agents.

  • Hepatitis-A  andE spread through consumption of contaminated food, milk, drinks, juices and water.

  • Former Baywatch beautyPamela Anderson has contracted the potentially fatal liver disease hepatitis-C by sharing a tattoo needle with her ex-husband Tommy Lee.

  • Brachytherapy : A special radiotherapeutical technique in which a very high doze of radiation is given to small volume of body tissues in short period from small radioactive sources like Radium, Cobalt-60, Iridium - 192, etc. Another advanced technique of radiation therapy of cancer isIntensity Modulation Radiotherapy (IMRT) in which non-uniform beams are fired on the affected organ from several angles to deliver desired doses to the tumour while minimising dose to surrounding organs.

  • Adjuvant vhemotherapy is the technique of using several drugs at the same time.

  • Monoclonal antibodies and interferous have been used against leukaemia, lymphosarcoma and breast cancers.

  • Leukemias are three types :Lymphocytic leukemia (increase in number lymphocytes, enlargement of lymph nodes, etc.);Granulocyotic leukemia andMonocytic Leukemia.  

  • Autoimmune diseases are kind of degenerative diseases as these involvedestouction of certain body cells.

  • Certain latest informations about AIDS :

    • AIDS - virus is a retro-virus so multiplies by the process of reverse transcription.

    • HIV has high mutability.

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