Immune System:

The immune system is a defense system that consists of many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism’s own healthy tissue. In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity.

The innate and adaptive immune systems

The immune system is the collection of cells, tissues and molecules that protects the body from numerous pathogenic microbes and toxins in our environment. This defense against microbes has been divided into two general types of reactions: reactions of innate immunity and reactions of adaptive immunity. Thus, innate and adaptive immunity can be thought of as two equally important aspects of the immune system. As you will see, each aspect differs with respect to how quickly it responds and for how long it responds to pathogens, its central effector cell types and its specificity for different classes of microbes.

As its name suggests, the innate immune system consists of cells and proteins that are always present and ready to mobilize and fight microbes at the site of infection. The main components of the innate immune system are;

1) Physical epithelial barriers
2) Phagocytic leukocytes
3) Dendritic cells
4) Natural killer (NK) cell
5) Circulating plasma proteins

The adaptive immune system, on the other hand, is called into action against pathogens that are able to evade or overcome innate immune defenses. Components of the adaptive immune system are normally silent; however, when activated, these components “adapt” to the presence of infectious agents by activating, proliferating, and creating potent mechanisms for neutralizing or eliminating the microbes. There are two types of adaptive immune responses;

1) Humoral immunity, mediated by antibodies produced by B lymphocytes
2) Cell-mediated immunity, mediated by T lymphocytes

Resources:
–http://missinglink.ucsf.edu/lm/immunology_module/prologue/objectives/obj02.html

Innate vs. adaptive immunity. Humoral adaptive immunity vs. cell-mediated adaptive immunity. Created by Sal Khan.

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