The human immune system is the combination of the body’s efforts to protect itself from the harmful effects of pathogens and other foreign substances, destroy diseased or weak cells, and remove cellular-level or even molecular-level debris. Using its own advanced structure and with the help of a special suite of organs, tissues, cells, and cell products, the body can build its defenses, recognize threats, react, fight pathogens, repair damage, and improve the defense, preparing for similar future invasions.
Derived from the regular leaking of flowing blood through its vessels and produced in various degrees by the spleen and the bone marrow, a special clear-yellowish fluid called lymph circulates in its own vessels throughout the body, containing white blood cells (fighting cells) that eventually make their way back into the blood stream through the flow of lymph and intermittent leaking. The lymphatic organ called the spleen is essential to the immune system, storing red blood and white blood cells for emergency response, filtering and cleansing blood, and producing both types of blood cells. Bone marrow is a type of soft connective tissue located in the interior of bones; it is the primary producer of blood, both white and red. White blood cells can be divided into five main types: lymphocytes, neutrophils, monocytes, basophils, and eosinophils, where neutrophils and monocytes are phagocytic (cellular debris eaters) and lymphocytes are the main type of immune response cells, including B cells, T cells, and NK cells, some of which can eventually differentiate into plasma cells. Plasma cells produce antibodies in response to a pathogen invasion that feature specific binding sites (locks) for antigens (keys) – molecular components of intruders that induce a specific type of immune system response, like the creation of antibodies to link to antigens in order to neutralize them.
Innate immunity is the immunity the body has by virtue of genetics – the type of antibodies and system inherited from the parents. Since there are billions of strands (versions) of pathogens, the types encountered by previous generations will most definitely differ from the strands faced by the body today, reducing the effect of innate immunity. Most of the body’s immunities are acquired throughout its life.
Passive immunity is gained through the transfer of readymade antibodies that can meet the threat. This type of immunity is very short-lived because the body does not produce its own version of antibodies and therefore doesn’t remember the antibody-antigen lock-key combination (for possibly different types of strands or under different conditions). Passive immunity is acquired naturally by a fetus while in its mother’s womb and through breast milk in the early periods of weaning, the readymade antibodies being transferred through the placenta or the breast milk. Passive immunity can also be acquired by immunization (shots) or antibiotics (typically pills to be ingested), when there is little time for the body to develop its own antibodies and is in need of a short-term supply. Again, the T cell and B cell memory cells will not be activated and the body will not have any way to remember this type of antigen, because the antibody is being imported (from the mother or through shots or pills).
Active immunity is acquired through the triggering of the immune response in the body by entry of an antigen, resulting in the activation of B cells and T cells that first analyze a pathogen’s antigen (key) and then produce the appropriate antibody (lock). They include memory cells that now can reproduce that same type of antibody quicker the next time they encounter this type of antigen. Active immunity can be naturally acquired when the body contracts a disease / disorder so that the immune system can be activated and consequently remember the type of antigens that intruded. Active immunity is artificially acquired by the injection of a vaccine – a substance resembling a pathogen that contains the antigen in a weakened form so that the immune system can create the appropriate antibody with ease and with little risk of introducing harmful substances into the body.
The human immune system is a very advanced mechanism of the body. It serves to build defenses, recognize threats, react, fight pathogens, repair damage, and improve the defense, preparing for similar future invasions. It accomplishes this by way of a defense suite located in every part of the body and which can be transported to the appropriate location by way of blood flow. It includes organs like the spleen, tissue like the bone marrow, white blood cells, and antibodies, working with the advanced structure of the body to provide protection and immunity. Innate immunity is what the body is ready for based on what is inherited and acquired immunity is what is acquired throughout the life of the body. This includes short-term immunity that a fetus or newborn gets from its mother and antibody import through shots or pills, and it includes long-term immunity achieved by fighting disease successfully and artificially-induced pathogens triggering the appropriate immune response.