Second Line of Defense

The second line major players:

The second line of defense is nonspecific resistance (innate immunity) that destroys invaders in a generalized way without targeting specific pathogens.

Dendritic cells (DCs) are a type of antigen-presenting cells (APC) located in the skin, mucosa and lymphoid tissues. Their main function is to process antigens and present them to the Third Line of Defense (T-cells) to promote immunity and tolerance to foreign antigens.

Macrophages are large phagocytic cells found in stationary form in the tissues or as mobile white blood cells, especially at sites of infection. Their job is to trap and break down foreign invaders. [phago = eat cyto = cell]

Neutrophils are a type of white blood cell. Of the 4 types of white blood cells, Neutrophils are the most plentiful, making up 55 to 70 percent of your white blood cells. Their job is to search out and destroy invaders.

Basophils are a type of white blood cell that have some role in immune surveillance (such as detecting and destroying very early cancers) and wound repair. They represent less than 1% of white blood cells.

Eosinophils are another type of white blood cell. They help fight off infections and play a role in your body's immune response. They can also build up and cause inflammation and can be indicative of an infection, allergic response, skin condition, or an autoimmune disorder. An eosinophil count is a blood test that measures the quantity of eosinophils in your body. Abnormal eosinophil levels are often discovered as part of a routine complete blood count (CBC) test.

NK (natural killer) cells are a population of lymphocytes (white blood cells) with both innate and adaptive immune features. They produce cytotoxic molecules and play a major role in the host-rejection of both tumors and virus-infected cells.

Mast Cells: in response to exposure to a perceived pathogen, mast cells set off a rapid inflammatory response to outside invaders, such as germs, viruses, and parasites. Mast cells play a crucial role in the activation of the allergy response. When a person has an allergy, mast cells are responding to harmless triggers as if they were a threat by releasing large amounts of histamine. We'll explore more about the body's response to allergens later.

Innate immune response in review:

Apply what you've learned: Immune quest

In this activity you will play a video game (it's actually pretty cool) where you will create a immune response using what you've learned! Watch the trailer below, download the free game, and play through level 1 to learn even more about the innate immune system. Your final score and some of what you will learn in this game will be part of your essential questions this week.

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