Group	Drugs	Effects
Stimulants	Amphetamines, cocaine, nicotine and tobacco	Accelerates the activity of the brain
Depressants	Alcohol, Barbiturates, Tranquilizers	Slows down the activity of the brain
Narcotic/ Analgesics	Opium, Morphine	Act as depressants on the Central Nervous System
Hallucinogens	Lysergic acid diethylamide (LSD), Phencyclidine	Distorts the way one sees, hears and feels
Stimulants, Depressants, Hallucinogens	Bhang (Marijuana), Ganja, Charas	Stimulating action on the CNS and affects the cardiovascular system

S.No	Diseases	Caustive agent	Site of infection	Mode of transmission	Symptoms
1.	Common cold	Rhino viruses	Respiratory tract	Droplet infection	Nasal congestion and discharge sore throat, cough and headache
2.	Mumps	Mumps cirus (RNA virus)Paramyxa cirus	Salivary glands	Saliva and droplet infection	Enlargement of the parotid glands
3.	Measles	Rubella virus (RNA virus Parmyxco),	Skin and respiratory tract	Droplet infection	Sore throat, running nose cough and fever. reddish rashes  on the skin, neck and ears
4.	Viral hepatitis	Hepatitis - B virus	Liver	Parenteral route blood transfusion	Liver damage, jaundice, nausea yellowish eyes, fever and pain in the abdomen
5.	Chicken pox	Varicella-Zoster virus (DNA Virus	Respiratory tract,skin and nervous	Droplet infection and direct contact	Mild fever with itchy skin, rash and blisters

(i) A vaccine is a biological preparation that provides active acquired immunity to a particular disease and resembles a disease-causing microorganism and is often made from weakened or attenuated or killed forms of the microbes, their toxins, or one of its surface proteins.
(ii) Vaccines "teach" our body how to defend itself when viruses or bacteria, invade it.
(iii) Vaccine initiates the immunization process. The vaccines are classified as first, second and third generation vaccines.
First generation vaccine:
(i) First generation vaccine is further subdivided into live attenuated vaccine, killed vaccine and toxoids.
(ii) Live attenuated live vaccines use the weakened (attenuated), aged, less virulent form of the virus
(iii) Eg. Measles, Mumps and Rubella (MMR) vaccine and the Varicella (chickenpox) vaccine, killed (inactivated) vaccines are killed or inactivated by heat and other methods. Eg. Salk's polio vaccine.
(iv) Toxoid vaccines contain a toxin or chemical secreted by the bacteria or virus.
(v) They make us immune to the harmful effects of the infection, instead of to the infection itself.
(vi) Eg. DPT vaccine (Diphtheria, pertussis and Tetanus), (Triple antigen).
Second generation vaccine: contains the pure surface antigen of the Pathogen. :
Eg. Hepatitis-B vaccine 
Third generation vaccine: contains the purest and the highest potency vaccines which are synthetic in generation. The latest revolution in vaccine is DNA vaccine (or) recombinant vaccine

(i) The primary lymphoid organ is thymus.
(ii) The secondary lymphoid organ is tonsils.
Role of Primary lymphoid organ: Thymus
(i) Thymus is most active during the neonatal and pre-adolescent periods.
(ii) The thymus is a flat and bilobed organ located behind the sternum, above the heart.
(iii) Each lobe of the thymus contains numerous lobules, separated from each other by connective tissue called septa (cross walls).
(iv) Each lobule is differentiate into an outer cortex and an inner medulla. Within each lobule, the developing T cells called thymocytes are arranged into an outer cortex and an inner medulla
(v) An inner medulla contains immature thymocytes and outer cortex has matured thymocyte
(vi) One of its main secretions is the hormone thymosin. It stimulates the T cells to become mature and immunocompetent. By the early teens, (upto 12-13 years) the thymus begins to atrophy and is replaced by adipose tissue (binding tissue).
Secondary lymphoid organ :
(i) The tonsils (palatine tonsils) are a pair of soft  tissue masses located at the back of the throat (pharynx ).
(ii) The tonsils are part of the lymphatic system which help to fight against the infections. They stop invading germs including bacterin and viruses.

It is a toxin produced by lysis of insected red blood cells in a person affected with malaria. This causes malaria symptoms such as fever, chills, shivering etc.,

The type of barrier that involves macrophages are the
(i) Phagocytic barriers which is a type of innate immunity.
(ii) In this mechanism, specialised cells such as monocytes, Neutrophils and tissue macro phages pha cytose and digest whole microorganisms.

The immune responses may be primary or secondary.
(i) The primary immune response occurs when a pathogen comes in contact with the immune system for the first time.
(ii) The secondary immune response occurs when a person is exposed to the same antigen again. During this time, immunological memory has been established and the immune system can start producing antibodies immediately. Within hours after recognition of the antigen, a new army of plasma cells are generated. Within 2 to 3 days, the antibody concentration in the blood rises steeply to reach much higher level than primary response. This is also called as "booster response".

Lysozyme present in saliva acts as an antibacterial agent and cleaves the bacterial cell wall.

(i) Primary Lymphoid organ: Thymus is a primary lymphoid organ.
Function: One of its main secretions is the hormone thymosin. It stimulates the T cell to become mature and immunocompetent.
(ii) Secondary Lymphoid organ: Tonsils is a secondary lymphoid organ.
The tonsils are part of the lymphatic system, which help to fight infections. They stop invading germs including bacteria and viruses.

Autoimmunity is due to an abnormal immune response in which the immune system fails to properly distinguish between self and non-self and attacks its own body. Our body produces antibodies (autoantibodies) and cytotoxic T cells that destroy our own tissues. If disease-state results, it is referred to as auto-immune disease.
Thus, autoimmunity is a misdirected immune response. Eg., Rheumatoid arthritis and multiple sclerosis

(i) An infection or tissue injury usually causes redness (rubber), swelling (tumor), pain (dolor). and production of heat (color) that may result in fever
(ii) Such localised expression is called inflammatory response, which occur due to release of certain chemical alarm signals such as histamine and prostaglandins.

Interferons: These are the proteins made and released by host cells in response to the presence of pathogens such as viruses, bacteria, parasites etc
RoIe: They inhibit viral infections and stimulate the entire immune system to fight disease. They also regulate many kinds of cell functions

(i) After getting into the body of the person, the virus enters into macrophages where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase.
(ii) This viral DNA gets incorporated into the DNA of host cells and directs the infected cells to produce viral particles.
(iii) The macrophages continue to produce virus and in this way acts like a HIV factory.
(iv) Simultaneously, HIV enters into helper T-Iymphocytes, replicates and produces progeny viruses. The progeny viruses released in the blood attack other helper T-lymphocytes. The process is repeated.
(v) During this period, the person suffers from bouts of fever, diarrhoea and weight loss. Due to decrease in the number of helper T lymphocytes, the person starts suffering from infections and becomes immune deficient and unabie to protect against any infection.

B and T cells are the two type of lymphocytes. Both are produced in the bone marrow.

S.No	B lymphocytes (B cells)	T lymphocytes(T cells)
i.	They stay in the bone marrow until they are mature.	T lymphocytes leave the bone marrow and mature in the thymus gland.
ii.	B cells can bind with antigens and produce antibodies or become memory cells.	T cells do not produce antibodies. They recognize antigen cells and destroy them presenting.
iii.	It is not classified into different types.	T cells are of two types. Helper T cells and KillerT cells.

S.No	Autoimmune disease	Immunodeficiency disease
i.	If the immune system of the body fails to distinguish foreign molecules from self, then it reacts destructively against the host's own molecules. This is known as autoimmune disease.	An immunodeficiency disease results from the failure of one or more components of the immune system which could be due to genetic reasons, radiation, infections etc.,
ii.	Eg: Multiple sclerosis is a autoimmune disease	Eg: AIDS is a Immunodeficiency disease.

The common cold has evaded medical sciences advances for two primary reasons:
(i) The first issue is that the colds are most often caused by a rhinoviruses-a large family of viruses with hundreds of variants. This makes vaccination an impossibility and gives our immune system a challenging task.
(ii) Secondly, these viruses evolve rapidly so even if we could produce vaccines to cover the full spectrum of rhinoviruses, they would quickly become resistant.

(i) Mild tremors to convulsions.
(ii) Severe agitation and fits.
(iii) Depressed mood.
(iv) Anxiety.
(v) Nervousness.
(vi) Restlessness.
(vii) Irritability.
(viii) Insomnia.
(ix) Dryness of throat.

(i) For Diphtheria:
Causal agent: Corynebacterium diphtheria.
Mode of Transmission: Droplet infection through breathing.
Symptoms: Fever, sore throat, hoarseness and difficulty in breathing
(ii) For Typhoid: 
Causal agent: Salmonella typhi
Mode of Transmission: Through contaminated food and water
Symptoms: Headache, abdominal discomfort, fever and diarrhea.

(i) Certain types of leukocytes (WBCs), such as polymorphonuclear leucocytes (PMNL), neutrophils, monocytes, and natural killer cells [NK cells] (a type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes
(ii) Besides the phagocytes there are natural killer cells (NK cells) in the body which kills virus infected and some tumor cells.
(iii) These cells are categorized under the cellular barriers.

In the 1950s, experiments conducted by Porter and Edelman revealed the basic structure of the immunoglobulin.
An antibody molecule is Y shaped structure that comprises of four polypeptide chains, two identical light chains (L) of molecular weight 25,000 Da (approximately 214 amino acids) and two identical heavy chains (H) of molecular weight 50,000 Da (approximately 450 amino acids). The polypeptide chains are linked together by di-sulphide (S-S) bonds. One light chain is attached to each heavy chain and two heavy chains are attached to each other to form a Y shaped structure. Hence, an antibody is represented by H₂L₂.
The heavy chains have a flexible hinge region at their approximate middles.
Each chain (L and H) has two terminals. They are C - terminal (Carboxyl) (or) -COOH and amino or N-terminal (or NH₂). Each chain (L and H) has two regions and they have variable (V) region at one end and a much larger constant (C) region at the other end.
Antibodies responding to different antigens have very different (V) regions but their (C) regions are the same in all antibodies.
In each arm of the monomer antibody, the (V) : regions of the heavy and light chains combine to form an antigen - binding site shaped to 'fit' a specific antigenic determinant.
Consequently each antibody monomer has two such antigen - binding regions.
The (C) regions that forms the stem of the antibody class and serve common functions in all antibodies.
The functions of immunoglobulin are agglutination, precipitation, opsonisation neutralization etc.