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Organisms must constantly protect themselves from harm caused by invaders such as bacterial and viral pathogens. The immune system delivers this protection via numerous pathways, but this can broadly be broken down into two arms, innate immunity and adaptive immunity. In this article, we explore both aspects of the immune response, how they come about, the key cells and molecules involved and their role in protecting us. Immunity definitionImmunity is defined as an organism’s ability to protect itself from anything that it does not recognize as self, such as a pathogen or toxin. How does the immune system tell self from non-self?In humans, all nucleated cells express distinctive surface molecules called major histocompatibility complex class I (MHC class I) that identify them as being self. Anything that does not posses these “self tags” may be recognized by the immune system as foreign and targeted. Anything that triggers the immune system is called an antigen. What is innate immunity?Innate immunity, also known as genetic or natural immunity, is immunity that an organism is born with. This type of immunity is written in one’s genes, offering lifelong protection. It is considered the more evolutionarily primitive immune system and consequently, as well as being found in vertebrates, is also found in various shapes and forms in plants, fungi and insects. The innate immune response is fast acting and non-specific, meaning it does not respond differently based on the specific invader that it detects.
What is adaptive immunity?Organisms are not born with adaptive immunity and it is not “hard wired” in their genes like innate immunity. It is acquired during their lifetime as a result of exposure to specific antigens, be that through natural means such as infection or by vaccination. Consequently, it is also known as acquired immunity. An adaptive immune response is much slower than an innate response, taking days or even weeks to develop on first encounter (the primary immune response), but is specific to the antigen(s) present and can retain a long term “memory” to enable a faster response if it is encountered again in the future. Adaptive immunity does it necessarily last throughout an organism’s entire lifespan, especially if it is not regularly re-exposed, although it can.
Innate vs adaptive immunity table The following table summarizes the primary differences between innate and adaptive immunity.
Which cells are involved in innate and adaptive immunity?There are many cell types with their own specific roles involved in immunity as summarized in the figure below. In the innate immune response, these include macrophages, neutrophils, eosinophils, basophils, mast cells and dendritic cells that are derived from myeloid progenitors. Natural killer cells also form part of the innate immune system but, unlike the other cells of the innate immune system, are derived from lymphoid stem cells. Cells involved in the adaptive immune response include B cells (or B lymphocytes) that differentiate into memory cells and plasma cells and a variety of T cells (or T lymphocytes), including T helper cells and cytotoxic T cells (also called cytotoxic T lymphocytes, CTLs and CD8+ T cells), that are derived from lymphoid stem cells. Natural killer T cells and gamma-delta T cells are part of both the innate and adaptive immune response. Cells of the innate and adaptive immune system, their origins and roles in the immune response. The role of immunological memoryImmunological memory is defined as “the ability of the immune system to respond more rapidly and effectively to a pathogen that has been encountered previously” but in reality, extends to antigens of any source, not just pathogens. As mentioned, we have memory B cells to thank for this capacity.
Which of the following is found in both innate and adaptive immunity?Natural killer T cells and gamma-delta T cells are part of both the innate and adaptive immune response.
What is the difference of innate immunity and adaptive immunity?Innate immunity is the body's first line of defence against pathogens. It is general and non-specific, which means it does not differentiate between types of pathogens. Adaptive immunity is a type of immunity that is built up as we are exposed to diseases or get vaccinated.
Which of the following statement are true regarding adaptive immunity?Thus, adaptive immunity requires exposure to antigen to develop, T and B lymphocytes are the major cells involved and it is a specific defence.
Which of the following statement is correct about immunity?Final answer: Preformed antibodies need to be injected to treat the bite by a viper snake is the correct statement with respect to immunity.
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