Test: Common Diseases in Humans & Immunity

• The antibody recognizes a small portion of the antigen called the antigenic determinant or epitope.
• Each antibody recognizes and binds to a specific antigen in a lock and key type model.
• The variable regions, which make up the two identical antigen-binding sites, are different in each specific type of antibody, giving these sites specific shapes that fit certain antigenic epitopes.
• The remainder of the molecule consists of light and heavy chain constant regions where these amino acid sequences vary little from antibody to antibody.

• Antigen-binding site:

  

• Snake antivenom is a medication made up of antibodies used to treat snake bites by venomous snakes. It is a type of antivenom.
• It is a biological product that typically consists of venom neutralizing antibodies derived from a host animal, such as a horse or sheep.
• The host animal is hyperimmunized to one or more snake venoms, a process which creates an immunological response that produces large numbers of neutralizing antibodies against various components (toxins) of the venom.
• The antibodies are then collected from the host animal, and further processed into snake antivenom for the treatment of envenomation.

The production of antibodies by plasma cells in response to an antigen is called active immunity and describes the host's active response of the immune system to an infection or to a vaccination.

• Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells). When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.
• B cells, also known as B lymphocytes are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system by secreting antibodies. B-cells bind to an antigen, receive help from a cognate helper T cell and differentiate into a plasma cell that secretes large amounts of antibodies.

• Japanese encephalitis (JE) is a disease spread through mosquito bites. 
• Symptoms usually take 5-15 days to develop and include fever, headache, vomiting, confusion, and difficulty in moving.
• Symptoms that develop later include swelling around the brain and coma.
• Japanese encephalitis is a serious disease that may cause death.

• Sporozoites enter the female Anopheles mosquito when they bite an infected person where these sporozoite fertilise and multiply in the stomach wall of the female Anopheles and stored in the salivary gland of mosquito till it is again transferred to the human body by a mosquito bite.
•  After entering the human body the sporozoites reach the liver cells, where they multiply. This is followed by their attack on red blood cells resulting in their rupture. The ruptured RBCs release a toxin called  hemozoin, which is responsible for high recurring fever, chills and shivering.
• Life cycle of malarial parasite in Female Anopheles mosquito:

• Microorganisms that cause disease are collectively called pathogens.
• Pathogens cause disease either by disrupting the body's normal processes and/or stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms.

• HIV progressively destroys certain types of white blood cells called CD4+ lymphocytes.
• Lymphocytes help defend the body against foreign cells, infectious organisms, and cancer. Thus, when HIV destroys CD4+ lymphocytes, people become susceptible to attack by many other infectious organisms.

HIV Infection:

The baby is given the following vaccines from the first month to the third month:

• 1 (½) DTaP (diphtheria, tetanus, acellular pertussis) vaccine.
• 2 (½) Hib (Haemophilus influenzae type b) vaccine.
• 3 (½) IPV (polio vaccine).

• Lymphocytes are one of several different types of white blood cells.
• Lymphocytes are of two types B cells and T cells.

1. When a macrophage engulfs organisms, B cells (humoral immunity) release antibodies which cause the destruction of bacteria.
2. The T cells (cell-mediated immunity) destroy the infectious organisms by killing the body cells that are affected.

Hence lymphocytes are a unit of the immune system.

• Congenital disorders, also known as congenital diseases or birth defects, are conditions present from birth.
• Both sickle cell anaemia and Huntington's chorea are congenital genetic disorders.
• Sickle cell anaemia was first discovered by James Herrick (1904). In this disease, the patient's hemoglobin level is reduced to half of the normal and the RBCs become sickle-shaped. A single mutation in a gene can cause sickle cell anaemia.
  
• Huntington's chorea is caused by autosomal mutation which is dominant. The gene is present on chromosome number 4. It is an inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain.
  

• Acquired Immune Deficiency Syndrome or AIDS is a set of symptoms caused by the HIV virus.
• It is in fact, the most advanced stage of infection caused by HIV.
• This disease modifies and corrupts the immune system, making people susceptible to infections and diseases.

The function of IgE antibody as mediators in allergic reactions of Type I is explained by their ability to interact both with antigen and with receptor molecules on the membrane of blood basophils and tissue mast cells. It is essential for type I hypersensitivity, which occurs as allergic asthma, rhinitis, and other allergic disorders. It also plays a key role in allergic reactions to anaphylactic medicines, bee stings, and antigen preparations used in immunotherapy tolerance.

1. ESR is done to check out the concentration of Erythrocytes in blood.

2. PCR is done to amplify the amount of DNA molecules.

3. Widal test is a serological test for typhoid or enteric fever.

4. ELISA is done in AIDS.

• Mosquitoes become infected when they feed on a person already infected with the virus.
• Infected Mosquitoes can then spread the virus to other people through bites.
• Chikungunya virus is most often spread to people by Aedes aegypti and Aedes albopictus mosquitoes. These are the same mosquitoes that transmit dengue virus.