Immunity is the body’s ability to protect itself against infection with germs. It includes barriers, such as skin and mucous membranes, that keep harmful substances out of the body, as well as the immune response, which fights against microorganisms once they’re inside. There are three types of immunity: innate, adaptive, and passive.
Innate immunity is protection you’re born with. It includes your skin and the special surfaces that line the respiratory, gastrointestinal, and genitourinary tracts. These protect against harmful germs and even nonliving things, such as a splinter. The innate system goes into action right away when it sees an invader and attacks any organism that shouldn’t be in your body. It doesn’t need prior training to know what invaders are and is not harmful to you.
Adaptive immunity is what you develop after exposure to certain microorganisms, such as bacteria, viruses, and fungi. It involves memory cells, which are white blood cells that recognize and remember certain invaders and can tell them apart. It also involves the immune response, which is a chain reaction that occurs when lymphocytes recognize an invader and work with other cells to kill it. Vaccines help support acquired immunity by teaching the immune system to identify and eliminate certain microorganisms.
Certain medical conditions, medications, and lifestyle factors can weaken the immune system, making it harder to defend against infection. Infections can cause many different symptoms, so it’s important to make an appointment with your healthcare provider if you think you may have a weak immune system.
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