Gonbup Comics©2017

Joke:

The interviewer:
Everything seems to be okay but I have a question about the relocation on your application. What happened?

The interviewee:
The company relocated, but they didn't tell me where.

Gonbup Comics©2017

Innate Immunity and Immune System Infection

     The immune system is our internal defense.

     There are many potentially dangerous viruses, bacteria, and other pathogens. They occur in the air, in the food, and in the water. There are also cells that abnormally develop into cancer. Our immune system has developed two types of defense against these threats. They are innate immunity and acquired immunity. 

     Let's look at innate immunity.

     Innate immunity is the kind of defense that is mediated by phagocytic (uptake) cells, antimicrobial proteins, the inflammatory response, and natural killer (eliminates tumors and viruses) cells. It is present before exposure to pathogens and is effective from the time of birth.

     The first lines of defense are the external defenses.  Intact skin and mucous membranes form physical barriers that bar the entry of microorganisms and viruses. Mucus produced by cells in these membranes, the low pH (acidic ranging from 3-5) of the skin and stomach, and degradation by lysozyme (emzyme that digests bacterial cell walls) also deter infection by pathogens.

     The second lines of defenses are the internal cellular and chemical defenses. Phagocytic cells (white blood cells) injest microbes that penetrate external innate defenses and help trigger an inflammatory response. Phagocytes attach to their prey via surface receptors that bind to certain structures found on many microorganisms, but not on normal body cells.  Complement proteins, interferons, and other antimicrobial proteins also act against invading microbes. In local inflammation, histamine and other chemicals released from injured cells promote changes in blood vessels that allow fluid, more phagocytes, and antimicrobial proteins to enter the tissues. Although heat and swelling are uncomfortable sensations, the enhanced blood flow and vessel permeability that cause them are critical to innate defense.  Natural killer cells induce the death of virus-infected cancer cells via apoptosis (programmed cell death).

     Invertebrate immune mechanisms are present, also.  Insects defend themselves by mechanisms similar in many respects to vertebrate innate defenses. The insect equivalent to blood, the hemolymph, contains circulating cells called hemocytes. Antimicrobial peptides and phenolooxidase are insect innate immune defenses.

     Defenses in vertebrates can be divided into innate and acquired immunity. If an invading pathogen reaches the body's external innate defenses, various internal innate defenses quickly come into play. The defenses provided by acquired immunity against specific pathogens develop more slowly. Some components of innate immunity also function in acquired immunity.