Since the moment you rolled out of bed this morning, you’ve probably encountered thousands of viruses, bacteria, parasites, and fungi. But thanks to immunity, your body is able to fight off these foreign invaders and protect itself.

Like a high-tech security system in a bank or store, the body’s immune system is multifaceted. The first line of defense is called nonspecific, or innate. This type of sweeping protection fends off all encroaching pathogens in the same way. It consists of a number of mechanisms, including the skin and the sticky mucous linings, such as those in the nose, lungs, and stomach, that trap small particles. If viruses or bacteria break through this initial barrier, white blood cells, natural killer cells, and other defending cells rush to destroy them. During this process, tissues react with an inflammatory response, bringing more blood into the affected area to attract defender cells that clear out the harmful particles and other types of cells that repair damaged areas. As another security measure, body temperature often rises, because most viruses and bacteria can’t thrive in hot temperatures.

The other type of immunity is a finely tuned adaptive system that releases specialized cells whose main purpose is to destroy a particular pathogen. Once exposed to a certain offending virus or bacteria, such as the chicken pox virus or Streptococcus bacterium, the body produces white blood cells called T lymphocytes (T cells) and tailor-made antibodies to fight off microbes of that type. That’s why people are typically safe from measles for the rest of their lives after one bout: These specialized cells are persistent in your body, and when you’re reexposed to that same virus, they rush to fight it off before it can make you sick. Vaccines essentially capitalize on this process. By introducing tiny amounts or harmless pieces of certain pathogens, such as the agents that cause the flu, measles, or whooping cough, vaccines prompt the body to produce focused antibodies that safeguard the body without its undergoing an illness.

ADDITIONAL FACTS

  1. The phlegm that causes your runny nose and congestion is made up of mucus and dead white blood cells.
  2. Stress, an unhealthy diet, and lack of exercise can weaken the immune system.
  3.  Although nearly all organisms have nonspecific immune systems, only higher-order vertebrates have an adaptive one as well.