Tag: immunity and blood groups

Vaccination is the administration of antigenic material (a vaccine) to stimulate an individual's immune system to develop acquired immunity to a pathogen. Upon administration of attenuated or inactivated antigen (vaccine), the antibodies are produced by plasma cells and memory cells are activated. When the same antigen attacks the person in future, the memory cells recognize the antigen and promotes phagocytosis.

A lymphocyte is one of the subtypes of white blood cell in a vertebrate's immune system. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic acquired immunity), and B cells (for humoral, antibody-driven adaptive immunity). The total number of lymphocytes present in healthy humans is approximately 1 trillion.

Active immunity is the induction of immunity after exposure to an antigen. Antibodies are created by the recipient and may be stored permanently due to the activation of memory cells which recognizes the same antigen in future and destroy them. Active immunity can occur naturally when a microbe or other antigen is received by a person who has not yet come into contact with the microbe and has no pre-made antibodies for defence.

The adaptive immune system, also known as the acquired immune system is composed of highly specialized, systemic cells and processes that eliminate pathogens or prevent their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates. Acquired immunity creates immunological memory after an initial response to a specific pathogen, and leads to an enhanced response to subsequent encounters with that pathogen.

The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or allergy. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. Histamine is released from mast cells. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling. 

• In our body, neutrophils, macrophages and lymphocytes are involved in the second line of defence. They produce non-specific immune responses such as fever and inflammatory response.
•  Neutrophils are a type of WBC and they form an essential part of the innate immune system. Neutrophils are one of the first-responders of inflammatory cells to migrate towards the site of inflammation.
• Macrophages are the type of WBC which engulfs and digests cellular debris, foreign substances, microbes etc..
• Lymphocytes are a type of WBC. It includes natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity). 

• Acquired immunity is the immunity obtained either from the development of antibodies in response to exposure to an antigen, as from vaccination or an attack of an infectious disease or from the transmission of antibodies, as from mother to fetus through the placenta or the injection of antiserum.
  
• Active acquired immunity results from the development of antibodies in response to an antigenic stimulus, as from exposure to an infectious disease or through vaccination.
• Hence, resistance developed in an individual as a result of antigenic stimulus is due to Active acquired immunity.

• Gammaglobulin is a class of globulins which are immune molecules that are produced by the immune system in response to the invasion of the body of agents that are perceived by the system as being foreign. Most significant globulins are immunoglobulins.
  
• Artificially acquired passive immunity is a short-term immunization by the injection of antibodies such as gamma globulin that are not produced by the recipient's cells.
  
• Hence, a person injected with gammaglobulin against hepatitis B is artificially acquired passive immunity.

Passive immunity is the transfer of active humoral immunity of ready-made antibodies (exogenous). Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus or child through the placenta or milk, and it can also be induced artificially when high levels of antibodies specific to a pathogen or toxin are transferred to non-immune persons through blood products that contain antibodies. Passive immunity is short-lived, as long as antibodies persist in the body. It is seen in cases where a patient needs immediate protection from a foreign body and cannot form antibodies quickly enough independently.