A student on a field trip suddenly felt breathlessness and started to sneeze very badly. Name this response and explain what it is due to.

The response in the given situation is allergy. Any exaggerated response to allergens (food, pollens, dust, or any foreign substance which was not otherwise harmful) is called allergy. In this, the body produces antibodies (I g E) against allergens. Allergy may be due to the release of some chemicals like histamine and serotonin from the mast cells. A person may feel inflammation, breathlessness, sneezing, headache, itching, etc.

Comment on the role of vaccination and immunisation in keeping the human population healthy.

The vaccines are the attenuated culture of disease-causing microorganisms that induce the production of antibodies against a particular disease. Thus, antibody provoking agents are called vaccines. The principle of immunisation or vaccination is based on the property of 'memory' of the immune system. The vaccines also generate memory-B and T cells that recognise the pathogen quickly. The process of introduction of vaccines into an individual to provide protection against disease is called vaccination. In vaccination, a preparation of antigen proteins of pathogen or inactivated/ weakened pathogens are introduced in the body. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection. The vaccines also generate memory B and T cells that help to recognise the pathogen quickly on subsequent exposure and overwhelm the invades with massive production of antibodies. In snake bites, the injection which is given to the patients contains preformed antibodies against the snake venom. This type of immunisation is called passive immunisation. Hence, the preformed antibodies or antitoxin from vaccination or immunisation protect our body from deadly microbes and against snake venom. Thus, it helps in keeping the human population healthy.

Differentiate between active and passive immunity.

Features Active Immunity Passive Immunity Definition Active immunity is developed by the antibodies that are produced by one's own immune cells in response to a foreign pathogen or vaccine. Passive immunity is developed by introducing preformed antibodies into the host body. Duration The developed immunity remains in the body for a lifetime. Example: A person who recovered from measles develops immune cells that will remain active for the rest of the patient's life. The immunity remains in the body for a temporary period. Example: The mother's colostrum rich in IgA provides passive immunity. Features Active Immunity Passive Immunity Response This immunity takes some time to develop. This immunity develops immediately. Memory This type involves primary and secondary immune response, where antibodies are produced from plasma and memory cells. It doesn't develop any immunological memory.

It is often observed that the chances of a person suffering from measles in his or her lifetime are low if he or she has suffered from the disease in their early childhood. Justify the statement.

Measles is an infectious disease caused by a type of virus called morbillivirus. This virus is spread from one person to another through direct contact with discharge from the nose or throat of an infected person or through airborne droplets from an infected person. Our body has a well-developed immune system that fights with foreign agents and keeps us disease-free. When morbillivirus enters our body, both cell-mediated and humoral responses get activated, which continuously fight with the virus. Through this process, memory B cells develop in our body against the morbillivirus. These cells circulate in the bloodstream in a quiescent state, and if the virus enters the body further, these memory B cells trigger an accelerated and robust secondary immune response. Thus, It is often observed that the chances of a person suffering from measles in their lifetime are low if they have suffered from the disease in their early childhood.