The Innate Immune System Response
When an invasion occurs, your innate immune system is the first to respond. It recognizes invaders by their antigens—unique proteins on the surface of the invading cell. Every cell has its own specific antigens. The cells that make up your body carry “self-antigens,” which are used by your immune system to distinguish self (you) from other (invader).
Your innate immune system utilizes several defense mechanisms to help protect you from foreign invaders. Skin cells and epithelial cells lining the openings of your body form tight junctions that make it difficult for invaders to get in. Hairs in your nasal cavity trap invaders, which prevents the invaders from moving into your lungs. Your body uses chemical factors, such as those contained in mucus or the acid in your stomach, to ward off invaders. The commensal (or good) bacteria that cover the surface of your skin and digestive tract provide another layer of protection.
The innate immune system response also activates certain immune system cells, which include neutrophils, macrophages, dendritic cells, and NK cells. These cells capture and destroy incoming invaders and send signals to other immune system components, which activates a more targeted immune system response against invaders.
The Adaptive Immune System Response
The role of your adaptive immune system is two-fold:
– It provides a second wave of immune system defense and works alongside your innate immune system to generate a more targeted response to incoming invaders.
– It generates immune system memory cells (more on these later).
An adaptive immune system response is initiated when invaders in your tissues are brought back to your lymph nodes by a group of cells called antigen-presenting cells (APCs). There are three types of APCs: dendritic cells, macrophages, and B cells.
When APCs encounter an invader, they ingest it, break it into pieces, and attach its antigens to their surface. The antigens presented on the surface of these cells serve as a signal that activates components of your adaptive immune system.
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