Tag: immunity and blood groups

The second line of defence involves non-specific cellular and molecular responses of the innate immune system because these defences do not differentiate between different types of the pathogen and respond the same way upon every infection. Mucous membrane, phagocytes and lysozyme are all involved in a non-specific defence mechanism, whereas, killer T-cells or cytotoxic T-cells provide the third line of defence.

• Physiological barriers to the entry of microorganisms in the human body are tears in eyes, saliva in mouth and HCl in the stomach.
• The enzymes lysozymes are found in tears and saliva inhibits the synthesis of peptidoglycan present in the cell wall of microorganisms especially eubacteria.
• Hence Tears acts as the physiological barrier to entry of microorganisms in the human body.
• So, the correct answer is 'Tears'.

Polymorphonuclear leucocytes (neutrophils) and monocytes are key components of the cellular barrier in the innate immune system, which phagocytose pathogens.

• Naturally acquired active immunity occurs when a person is exposed to a live pathogen and develops a primary immune response. An example is acquired after smallpox infection.
•  Naturally acquired passive immunity occurs during pregnancy, in which certain antibodies are passed from the maternal blood into the fetal bloodstream in the form of IgG.
• Artificially acquired active immunity can be induced by a vaccine, a substance that contains antigen. An example of artificial active immunity is building up a resistance to a disease due to immunization.
•  Artificially acquired passive immunity is a short-term immunization by the injection of antibodies, such as gamma globulin, that is not produced by the recipient's cells. eg: Antirabies serum,
•  So, the correct answer is 'a - iii, b - iv, ci, d - ii'.
  

• Immunity to viral infection is caused by a variety of specific and nonspecific mechanisms. 
• The activation of different immune functions and the duration and magnitude of the immune response depending on how the virus interacts with host cells. 
•  Cytotoxic T lymphocytes, natural killer (NK) cells and antiviral macrophages can recognize and kill virus-infected cells.
•  Hence, Body cells infected by viruses are destroyed mostly by Natural Killer cells.
• So, the correct answer is 'Natural Killer cells'.

Passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta and through colostrum (mother's milk), and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin (obtained from animals) are transferred to non-immune persons through blood products that contain antibodies. Passive immunity is short lived.

• Cytokine inhibits viral replication.
• They form an innate immune system by forming physical barriers. 
•  Virus-infected cells secrete proteins called interferons which protect non-infected cells from a further viral infection is a cytokine barrier. Hence, The cytokine barrier among these is interferon.

Artificially acquired passive immunity explains this form of protection. When performed antibodies are directly injected into the body, it is known as artificial passive immunity. It provides the quick immune response. In case of snake bites, the injection which is given to the patients, contain performed antibodies against snake venom. This type of immunisation is passive immunisation.

Passive immunity involves the transfer of pre-formed antibodies (serum, gamma-globulin). Attenuated microorganisms are used in vaccines to stimulate the body to produce its own antibodies, which is the definition of active immunity.