Vaccination and Immunity

A macrophage is a type of phagocyte, which is a cell responsible for detecting, engulfing and destroying pathogens and apoptotic cells. Macrophages are produced through the differentiation of monocytes, which turn into macrophages when they leave the blood. Macrophages also play a role in alerting the immune system to the presence of invaders. Phagocytosis is the term used to describe the engulfing and destroying of defective or microbial cells. When inflammation occurs, monocytes undergo a series of changes to become macrophages and target cells that need eliminating. Once engulfed, cellular enzymes inside the macrophage destroy the ingested particle. Some macrophages act as scavengers, removing dead or necrotic cells while others provide host immunity by engulfing microbes.

An antibody also known as an immunoglobulin (Ig) is a large, Y-shaped protein molecule produced by B lymphocytes, that is used by the immune system to identify and neutralize pathogens (antigens) such as bacteria and viruses.

The cells involved in the immune system are white blood cells, or leukocytes, which destroy disease-causing organisms or substances. The two types of leukocytes are phagocytes and lymphocytes. The most common type of phagocyte is the neutrophil, which primarily fights bacteria. The two kinds of lymphocytes are B lymphocytes and T lymphocytes. Lymphocytes form in the bone marrow and either stay there and mature into B cells, or they leave for the thymus gland, where they mature into T cells.

Leucocytes or the white blood cells are the disease-fighting white blood cells that identify and eliminate pathogens. Hence, they are one of the chief components of the innate immune system. A high white blood cell count is referred to as leucocytosis. The innate leucocytes include phagocytes (macrophages, neutrophils and dendritic cells), mast cells, eosinophils and basophils.

In humans, the Major Histocompatibility Complex (MHC) is referred to as the Human Leukocyte Antigen (HLA) system.

Active immunity involves the active functioning of the person's own immune system leading to the synthesis of antibodies on the entry of the antigens into the body.

Treatment for a snake bite from a venomous snake like a viper involves the injection of preformed antibodies (antivenom) because the body cannot produce them fast enough to neutralize the toxin.

Colostrum is the name given to the first milk produced by the mammary glands of mammals. It consists of various antibodies that provide natural passive immunity to the newborns. This immunity is transient and does not have a latent period or a negative phase.

Colostrum is the form of milk produced by the mother, after the birth of the baby. This is the first milk and is known to contain nutrients, proteins, antibodies and many growth factors essential for the growth and development of immunity in the baby. This milk contains high amounts of IgA. This antibody is required to protect the mucous membranes present in the throat, lungs and intestine of the baby from infection. 

Rickettsial or viral vaccines are produced by cultivating microorganisms in living tissues of animal bodies, such as chick embryos. It is possible in some cases to reduce these effects by harvesting only proteins of the infected tissues. E.g., allantoic fluid of chick embryo. These viruses can be killed or inactivated with formaldehyde, phenol etc. 

An allergen is a type of antigen which are non-infectious that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies. The production of allergens stimulates the release of IgE (immunoglobulin E) antibodies. These IgE antibodies bind to the allergens and then activates receptors of mast cells which triggers the release of inflammatory chemicals such as histamine. Hence, allergens induce disorders through secretion of IgE and histamine.

Interferons are signaling proteins released by host cells in response to the presence of several viruses. They cause nearby cells to heighten their anti-viral defenses.