Immune System

Zero To Finals

The immune system exists in organisms as a method to defend the body against "foreign" invaders or pathogens, agents that can cause disease and infect a wide range of animals. This system is a network of cells, tissues, and organs that all work together to achieve this goal. There are two types of immunity:

Innate Immunity exists in all invertebrates and vertebrates and becomes active immediately upon infection. This type of immunity is a nonspecific response to pathogens. The innate immune system will react to anything is identified as "non-self". The first line of defense in this system are barrier defenses such as skin and mucus membranes. Internal defenses consist of phagocytic cells, natural killer cells, and an inflammatory response.

Adaptive Immunity exists only in vertebrates. Adaptive immunity develops over a longer period of time and is activated after the innate immune response. This response is a very specific response to pathogens. The adaptive immune system builds memory of pathogens through T and B lymphocytes. This ensures a fast response should pathogens ever try to re-infect a vertebrate host.

T Cells

T lymphocytes are part of the adaptive immune system. These cells develop in the Thymus, where they undergo rigorous testing to ensure they will not react strongly to a host's own cells. Once activated, T cells proliferate and become either cytotoxic T cells, or helper T cells. Cytotoxic T cells trigger apoptosis in infected cells.

B Cells

B lymphocytes are also part of the adaptive immune system. These cells develop in bone marrow, recognize and bind to antigens that are found in circulation, releasing antibodies that help neutralize pathogens in the blood and lymph. Once activated, some B cells will become memory cells, so they can live to identify the pathogen in the future.

Immunity In Marine Iguanas

As vertebrates, marine iguanas (like other reptiles) have both an innate and adaptive immune system. The innate immune system of reptiles is broad and robust, providing a strong initial response to pathogens. Less is known about the adaptive immune system of reptiles, and specifically marine iguanas. Though their immune system is comprised of T and B cells, their immune response is slower and broader. This is hypothesized to support a greater innate immune response. Additionally, the role of cytotoxic T cells has not been determined in the adaptive immune system of reptiles.

Seitz et al. 2021

Avian Poxvirus

One of the main disease threats marine iguanas face in infection by avipoxviruses. This viral disease affects a wide range of bird species, and transmission is possible through mosquitos and contact of skin abrasions. Unable to complete its lifecycle in non-avian species, poxvirus infection in reptiles has been observed to cause skin lesions and mortality.

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