Vaccination and Immunity

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.

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.

Artificially acquired passive immunity is a short-term immunization achieved by the transfer of antibodies, which can be administered in several forms such as human or animal blood plasma or serum. Antivenine is an antisera which is obtained from the snake poison and it is transferred to the person with snake bite. It is used to provide immediate immunity in case of emergency.

• When the immune system is activated due to the viral infection or other immune response the white blood cells in our body produces Interferons (are a group of proteins called cytokines). Interferons inhibit viral multiplication
• The name of the interferons comes from their ability to interfere with the production of new virus particles. Interferons do not directly kill viral or cancerous cells; they boost the immune system response and reduce the growth of cancer cells by regulating the activity of several genes that control the secretion of numerous cellular proteins that affect growth.
• Hence cytokine that provides nonspecific immunity against viruses is Interferon.
• So, the correct answer is 'Interferons'.

The acquired immune system, also known as the adaptive immune system is a subsystem of the overall immune system that is composed of highly specialized, systemic cells and processes that eliminate pathogens or prevent their growth. 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. Acquired immunity distinguish between self and non-self and produce antibodies against the non-self antigen.

Cytokines are a broad category of small proteins that are important in cell signalling. Their release has an effect on the behaviour of cells around them. Proinflammatory cytokines are produced predominantly by activated macrophages and are involved in the up-regulation of inflammatory reactions. There is abundant evidence that certain pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α are involved in the process of pathological pain.

Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. They are essential for fighting infections and for subsequent immunity. Phagocytes provide the second line of defence which is considered as a non-specific defence because it destroys invaders in a generalized way without targeting specific pathogens. Phagocytes are activated when the pathogen is able to cross the first line of defence.

Neutrophils are the most abundant type of granulocytes. They form an essential part of the innate immune system. Neutrophils undergo a process called chemotaxis via amoeboid movement, which allows them to migrate toward sites of infection or inflammation. Neutrophils express and release cytokines, which in turn amplify inflammatory reactions by allowing other neutrophils, monocytes, eosinophils attachment to endothelium and dilation of capillaries is seen to increase the blood flow to the affected area.

Chemical barriers protect against infection. The skin and respiratory tract secrete antimicrobial peptides such as the β-defensins. Enzymes such as lysozyme and phospholipase A2 in saliva, tears, and breast milk are antibacterial substances. Vaginal secretions serve as a chemical barrier following menarche, when they become slightly acidic, while semen contains defensins and zinc to kill pathogens. In the stomach, gastric acid serves as a powerful chemical defence against ingested pathogens.