History is gone; they taught us the definitions, the experiments that lead to the discovery of this wide network of cells and organs that contribute to immunity.

But what comprises these networks individually?? Let’s see…

Well consider this diagram,

[1] Image source: Snapshot from ‘Overview of Immune System’ from www.handwrittentutorials.com

In this diagram you can see a pathogen has invaded the body, one of the cells involved in immune system is responding to it. Like this our body has to tolerate thousands and thousands of pathogen and in response to it our body has prepared for it by generating an enormous variety of cells and molecules capable of specifically recognizing and eliminating an apparently limitless variety of foreign invaders. These cells and molecules act together in a dynamic network.

To have a clear look at this dynamic network let’s understand each of these Cells and Organs individually.

Before going into detail about them, here is a look at each component.

Source: National Cancer Institute, Slide 1 The Immune System, https://www.cancer.gov

Source: National Cancer Institute, Slide 1 The Immune System, https://www.cancer.gov

We have heard about these two terms....Innate and Adaptive Immunity.

What are they?

Classifying Immune System

Source: Figure 1, overview of the Immune system, Immunology, Microbiology and Immunology online, University of South Carolina School Of Medicine.

Immunity—the state of protection from infectious disease —has both a less specific and more specific component. The less specific component, innate immunity, provides the first line of defense against infection. Most components of innate immunity are present before the onset of infection and constitute a set of disease-resistance mechanisms that are not specific to a particular pathogen but that include cellular and molecular components that recognize classes of molecules peculiar to frequently encountered pathogens. [3]

The elements of the innate (non-specific) immune system (Table 2) include anatomical barriers, secretory molecules and cellular components. Among the mechanical anatomical barriers are the skin and internal epithelial layers, the movement of the intestines and the oscillation of broncho-pulmonary cilia. Associated with these protective surfaces are chemical and biological agents. [4]

In contrast to the broad reactivity of the innate immune system, which is uniform in all members of a species, the specific component, adaptive immunity, does not come into play until there is an antigenic challenge to the organism. Adaptive immunity responds to the challenge with a high degree of specificity as well as the remarkable property of “memory.” Typically, there is an adaptive immune response against an antigen within five or six days after the initial exposure to that antigen. Exposure to the same antigen sometime in the future results in a memory response: the immune response to the second challenge occurs more quickly than the first, is stronger, and is often more effective in neutralizing and clearing the pathogen.[3]

Refrences:

[1] www.handwrittentutorials.com

[2] National Cancer Institute, Slide 1 The Immune System, https://www.cancer.gov

(https://www.cancer.gov/cancertopics/understandingcancer/immunesystem/AllPages)

[3] Chapter 2, Cells and Organs of Immune System, Immunology, Kuby, 5^th Edition.

[4] Immunology, Microbiology and Immunology online, University of South Carolina School Of Medicine. Link : https://pathmicro.med.sc.edu/ghaffar/innate.htm