BT302 Midterm Highlighted Handouts by WTT

Chapter# 1: Overview of the Immune System as the · Body’s main Defense Mechanism · Introduction to basic Terminology · Immunity

It is the resistance to disease specifically infectious disease or infections.

Immune system

The collection of cells, tissues and molecules that mediate resistance to infection is called as immune system

Immune response

The coordinated reaction of cells and molecules of immune system against infectious microbes is termed as immune response

Immunology

The study of immune system & immune response with physiological function to prevent infections and to eradicate established infections inside body

Infectious vs Non-infectious diseases

Infections

These are contagious, transmittable and communicable diseases which are caused by an invading or infectious agent. The infectious agent is a foreign particle to body’s immune system. These can be microbes like bacteria, viruses, fungi and parasites. That’s’ why infections can be bacterial, viral, fungal and parasitic in nature for example typhoid is a bacterial infection while hepatitis is a viral infection. Infections can be transmitted from one individual to other through various ways like aerosols, blood and also from mother to fetus.

Non-infections

These are non-communicable and non-contagious diseases in contrast to infections. These are not caused by purely by an infectious or invading agents but these agents can be a secondary reasons for such kind diseases for example in case of most of cancers are caused by various infectious agents secondarily. Non-infectious diseases are generally considered as metabolic disorders in which there is any defect in the metabolism of any bio-molecule for example diabetes mellitus is a carbohydrate metabolic disorder. These disease also have the tendency to transmit genetically from one generation to other.

Role of Immune System

The importance of the immune system for health is evident by the conditions when individual suffering from various fetal diseases in case of defective immune response. The most important function of immune system is to protect the body from the attack of infectious or invading microbes. If the individual’s immune system does not work properly then the chances of acquiring infections also increased for example in case of Acquired immunodeficiency syndrome (AIDS). This indicates the importance of immune system for defending against infections. Similarly, there is also very significant role of immune system in organ transplantation. Immune response act as a barrier for successful organ transplantation as immune system recognizes and responds to tissue graft and newly introduced proteins. Immune system also provides surveillance against tumors and cancers. Moreover, for treatment of cancers immunotherapy also have good implications. The products of immune system like antibodies are highly specific molecules for detecting any kind of molecules. Likewise, antibodies are widely used for developing immunologic approaches for laboratory testing in clinical medicine and research.

Types of Immunity

For providing defense against various infections, there are two important types of immunity

1. Innate or non-specific Immunity
2. Adaptive or specific immunity

Innate Immune System It is a non-specific immune system which serve as the first line of defense against pathogens. Innate immune system is readily available all the time in order to fight against microbes. Moreover, this form of immune system is also antigen independent and non-specific. There is immediate maximal response from innate immune system against attacking pathogens. Innate immune system lack in memory against the various forms of infections Adaptive Immune System It is considered as the second line of protection against various pathogen specifically. It needs activation after invasion by pathogen in a very specific manner. This system is antigen dependent with specificity. For the activation of adaptive immune system, it needs lag time for fully activation during which naive cells become active after differentiation and activation. Adaptive immune system has the unique attribute of memory against specific nature of pathogens.

Components of Innate Immune system

Innate immune system is the first line of defense against invading pathogens. It is comprised of following three important components or barriers

1. Anatomical barriers
2. Humoral (Secretory) barriers
3. Cellular barriers

Anatomical barriers Those defensive mechanisms which are related to various structures of body are the part of anatomical barriers. These are composed of three major arms including a) Mechanical arm b) Chemical arm c) Biological arm Mechanical Arm It is comprised of various mechanical defense by different structure of body for example like skin which is considered as a physical barrier for protection against invading agents. Similarly, the lining epithelium membrane of various body cavities like GIT & skin in the form of squamous epithelium which has the property of desquamation in order to get rid of infectious agent. Moreover, the peristalsis and cilliary movements of GIT also protect from the ingested