Question

Suppose you lacked all innate or nonspecific defenses.

a. First, list exactly what you would be missing.

b. Second, for each item, describe how life would be different without that mechanism.

c. For as many of the listed items as possible, invent some behavioral changes that would promote your survival

Answer 1

a. Innate immune responses or non-specific defenses include the following:

i) Anatomical Barriers that include Skin (epithelium), gastrointestinal and respiratory tract, cilia of nasopharynx, eyelashes of eye, body hair. These barriers prevent entry of viruses and bacteria.

ii) Secretions such as bile, mucus, gastric acid, saliva, tears, sweat. Sweat contains lysozyme and phospholipase.

iii) Inflammation, coagulation system, complement system and non-specific cellular responses. Non-specific cellular responses include: lactotransferin and transferrin, lysozyme, interleukin-1, surfactants, normal flora.

b. If these innate immune systems are absent:

i) Anatomical barriers: Absence of skin will allow all invading organism entry to the internal organs. The bacteria would be able to contact blood vessels easily, allowing it access to blood circulation. Absence of cilia and peristalsis would cause pathogens to infect the lungs and gastrointestinal tract. Eyelashes prevent entry of pathogens and small particles into the eye. This function is lost f eyelashes are absent. Body hair regulates body temperature as well as protects the body against dust and infiltrates that may get access to internal structures if removed.

ii) Secretions: Bile is required for defense against bacteria infections. If bile is absent, then bacteria can proliferate in the small intestine as well as mucosal injury. The biliary tract will also be breached by bacteria. Secretory IgA present in bile prevents adhesion of bacteria as well as anti-microbial actions. If saliva is absent, then the mouth is infected by pathogenic bacteria. Tears prevent microbial infection in mouth. Both have fatty acids that prevent growth of bacteria

iii) Other defenses: Defensins in lung and GI tract have antimicrobial activity that will eb lost if absent. Lack of sweat will decrease presence of anti-microbial peptides that interact with cell membrane. Hence, immunity against bacterial infections such as MRSA is lost. Surfactants such as opsonins if lost will decrease phagocytosis in lung. If there is no normal flora in the intestine and ski, then pathogenic bacteria can colonize and attach to these surfaces and induce infection. Lack of inflammatory responses, will not induce fever and allow the bacteria to easily infect. Similarly, complement is involved in cell lysis of bacteria, which will be lost.

c. Behavioral changes can be induced when such innate immune responses are absent. If tears and eye lashes are absent, then increased visual perception of threat can be induced. If the eyesight is improved, then closing of eyes in response to threat can prevent, infections. Visual perception of diseased looking people can lead to avoiding of contact with such people. It is also known to increase production of WBC in the body.

Similarly, if skin is breached, then the wound can be covered by antiseptic/ antibacterial solution. Vaccination is another method of preventing infections. Even if the bacteria can gain entrance to the body due to lack of anatomical barriers, the B cells will induce antibody production, which kill the bacteria. Covering the nose and mouth in dust pollution or when the speaking to an infected person, will limit the pathogens entering via nose and mouth. Wearing protective eye gear will also limit bacteria entering the eye. Increased oxygenation which is pure will improve lung function.