Innate Immunity
As you may know, the body has several structures that serve as protective barriers against infection. These include the skin, respiratory and digestive tract mucous membranes, and other structures.
The term immunity refers to the many structures and responses the human body has for preventing pathogens from entering the body and for fighting them off if they do get in.
Immunity can be broadly divided into two categories: innate immunity and adaptive immunity. Innate immunity is the body’s general response to invading pathogens—it’s the same in
everyone and reacts the same way each time. Essentially, we are born with innate immunity all ready to go.
Innate immunity includes physical barriers, such as the skin, and chemical responses, such as antimicrobials found in tears. It also includes physiological responses, such as fever and inflammation. These processes stimulate immune cells to take action, hinder pathogen growth, and prepare damaged tissues for repair. Specialized cells, like macrophages, can kill and digest bacteria and parasites, as well as secrete cytokines that can induce inflammation and mobilize other parts of the immune system.
An inflammatory response causes blood vessels to dilate, bringing more blood to the site and causing localized heat. The vessels also become leaky, allowing fluid and immune cells to leave the bloodstream and enter the infected tissue. The cardinal signs of inflammation are swelling, redness, and heat, and often there is pain and loss of function.
Adaptive Immunity
Now let’s have a look at the other arm of the immune system: adaptive immunity.
Adaptive immunity is the body’s way of mounting an immune response that is specific for each pathogen. B- and T-lymphocytes, or B- and T-cells are central to adaptive immunity. They are able to recognize each kind of invading pathogen and respond with a large, focused response tailored to that specific invader. What’s more, each time a new pathogen is found, the lymphocytes that recognized it will multiply and remain in your body so that if that pathogen ever returns, your immune response will be swift and massive.
