Innate resistance overview & immunity,immunity meaning,what is immunity,humoral immunity,herd immunity

       To establish an infection, an invading microorganism must first overcome many surface barriers, such as

 - skin, degradative enzymes, and mucus,

 - that have either direct antimicrobial activity or 

 - inhibit attachment of the microorganism to the host.

 - Because neither the surface of the skin nor the mucus- lined body cavities are ideal environments for the vast majority of microorganisms, 

 -  Most pathogens, or disease-causing microorganisms, must breach these barriers and reach underlying tissues to cause disease.

         However, any microorganism that penetrates these barriers encounters two levels of host defenses:

1. Innate resistance mechanisms and
2. Adaptive immune response.

- Animals (including humans) are continuously exposed to microorganisms that can cause disease.

- Fortunately animals are equipped with an immune system that usually protects against adverse consequences of this exposure.

- The immune system is composed of widely distributed proteins, cells, tissues, and organs that recognize foreign substances, including microorganisms.

- Together they act to neutralize or destroy them, maintaining host integrity.

            

                 immunity

           Immunity: (Latin immunis, free of burden) refers to the general ability of a host to resist infection or disease.

- Immunology is the science focused on immune responses to foreign substances and how these responses are used to resist infection.

- It includes the distinction between "self" and "nonself" and all the biological, chemical, physiological, metabolic, and physical aspects of the immune response.

- There are two fundamentally different yet complementary components of the mammalian immune response.

1. The first component arises by virtue of being a vertebrate animal.Vertebrates have evolved to express unique features that inherently protect against invasion by foreign substances. Some of these features are physical and act as barriers.

2. chemical in nature and directly kill or inhibit invaders.

- Still other features result when specialized cells recognize generic yet highly conserved chemical motifs (expressed on bacteria, fungi, and viruses) and initiate processes to engulf and degrade the foreign substance.

- These features are collectively called the innate resistance

mechanisms.

- The second component of the mammalian immune response is much more sophisticated, being directed by highly specialized cells that can respond to specific invaders through

- receptor-mediated capture events,

- be programmed to "remember" their encounters with foreign substances,

- amplify individual responses, recruiting other components of the host immune system to eliminate or reduce the threat posed by the invader.

Innate resistance mechanisms, also known as

- nonspecific resistance and

- innate, nonspecific, or

- natural immunity,

- is the first line of defense against any foreign material, including microorganisms, encountered by the host.

- It includes general mechanisms inherited as part of the innate structure and function of each animal (such as skin, mucus, and constitutively produced antimicrobial chemicals such as lysozyme).

- Innate resistance mechanisms defend against foreign invaders equally and to the same maximal extent each time a foreign invader is encountered.

Adaptive immune response, also known as

- Acquired or

- Specific immunity, defends against a particular foreign agent.

- The effectiveness of adaptive immune responses increases on repeated exposure to foreign agents such as viruses, bacteria, or toxins; that is to say, adaptive responses have "MEMORY.

- ANTIGEN: Substances recognized as foreign that provoke immune responses

Also known as immunogens (immunity generators).

- The presence of foreign antigens causes specific cells to replicate and manufacture a variety of proteins that function to protect the host. One such cell, the B cell, produces and secretes glycoproteins called ANTIBODIES.

- Antibodies bind to specific antigens and inactivate them or contribute to their

elimination.

- Other immune cells become activated to destroy host cells harboring intracellular  destroy host cells harboring intracellular pathogens, such as viruses.

- Innate resistance mechanisms and the adaptive immune responses work

together to eliminate pathogenic microorganisms and other foreign materials.

 -innate systems react immediately upon initial exposure to foreign

substances,

- multiple bridges occur between the two immune system components .

- variety of cells function in both innate and adaptive immunity, These cells are known as the white blood cells, or leukocytes.

- White Blood cell development occurs in the bone marrow of mammals during the process of hematopoiesis.

- Leukocytes function in the innate system, whereas others are part of a specific immune response.

- Some are important because they link the innate arm of the immune system to the adaptive.

- The leukocytes form the basis for immune responses to invading microbes and foreign substances. Many of these cells reside in specialized tissues and organs. Some tissues and organs provide supportive functions in nurturing the cells so that they can mature and respond correctly to antigens.