Tag: immunity and blood groups

The immune system has two divisions-humoral immunity and cell-mediated immunity. The humoral immunity protects against extracellular pathogens while the cell-mediated immunity protects against intracellular pathogens.

Activated B cells differentiate into either antibody-producing cells called plasma cells that secrete soluble antibody or memory cells that survive in the body for years afterwards in order to allow the immune system to remember an antigen and respond faster upon future exposures.

The activity of complement components is modulated by a system of regulatory proteins that prevent tissues damage as a result of inadvertent binding of activated complement components to host cells or spontaneous activation of complement components in plasma.

• Mast cells are found in mucous membranes and connective tissues and are important for wound healing and defense against pathogens via the inflammatory response.
• The mast cell granules are composed of serotonin, heparin, and histamine. They secrete serotonin, heparin, and histamine when they are activated in the presence of the toxic substance or a pathogen.
• Hence Mast cells secrete 'serotonin, heparin, and histamine'.
• So, the correct answer is 'All the above'.

• The cells of the immune system can be categorized as lymphocytes (T-cells, B-cells and NK cells), neutrophils, and monocytes/macrophages. These are all types of white blood cells.
• Neutrophils are phagocytic cells that are also classified as granulocytes because they contain granules in their cytoplasm. These granules are very toxic to bacteria and fungi and cause them to stop proliferating or die on contact.
  
• B lymphocytes provide humoral immunity and T lymphocytes provide cellular immunity.
• Macrophages are efficient phagocytic cells that can leave the circulatory system by moving across the walls of capillary vessels. The ability to roam outside of the circulatory system is important because it allows macrophages to hunt pathogens with less limits. Macrophages can also release cytokines in order to signal and recruit other cells to an area with pathogens.
• Hence Neutrophils, Lymphocytes, and Macrophages are involved in body defense.
• So, the correct answer is 'All the above'.

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 through the placenta, 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.

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 immune system will eventually create antibodies for the microbe, but this is a slow process.

Antivenum which is injected to body in case of snakebite, contain antibodies that disable a particular venom's toxins. Antivenom is less able to reverse the damage already happened in the body. So, quick injection is a must. So, the statement A is correct.

Innate immunity includes anatomical and physiological barriers, inflammation, complement activation, cytokine secretion, phagocytosis. Cytokines play an important role in the innate immune response. It fights directly against the virus by preventing its replication. At the same time, cytokines activates NK cells and macrophages, which produce more cytokines. Also, virus infected cells secrete proteins called interferons , which protect non-infected cells from further infection.