Overview of the Immune System Subscribe
Date: 06. November 2017
In this lecture educator presents the Overview of Immune system. In the first section of the lecture Historical perspective of Immune system is presented. The earliest report date back to 430 BC that was by a historian, Thucydides, historian of the Peloponnesian War. He provided first hint and idea towards immune system. Then for next 2000 years nobody paid attention to this mechanism, then Deliberate Immunity was introduced by Chinese and Turks in fifteenth century. They introduced Variolation that is a mechanism in which dried crusts from smallpox were inhaled. Lady Mary Wortley Montagu in 1718 saw potential in mechanism of variolation. Edward Jenner was the first person who came up with the idea of vaccine. He made a very important discovery against the small pox.
Louis Pasteur actually found that how the whole system of immunization works. He did a lot of experiments and grew bacterium for fowl Cholera. Earlier Studies of Immune components also involves the studies of Emil von Behring, Kitasato Shibasaburō and Elvin A. Kabat. Emil von Behring, and Kitasato Shibasaburō are two scientist who actually suggested that the Immunity can be transferred from Serum. Serum is the non-cellular part of the blood.
1900, Jules Bordet introduced that specific immune reactivity to non-pathogenic substances. Karl Landsteiner introduced the Generation of specific Abs through any organic chemical. Paul Ehrlich in 1900 introduces side-chain receptors, Instructional theories and Clonal selection theory are then presented.
Innate immunity is the inborn ability of body to defend again pathogen and viral diseases. In the start of second section educator explains the skin and mucosal surfaces in detail with illustrations. Innate immunity can be seen to comprise four types of defensive barriers: anatomic, physiologic phagocytic, and inflammatory. The skin and the mucosal surfaces provide protective barriers against infection. Physical and anatomic barriers that tend to prevent the entry of pathogens are an organism’s first line of defense against infection. The skin and the surface of mucous membranes are included in this category because they are effective barriers to the entry of most microorganisms. The skin consists of two distinct layers: a thinner outer layer—the epidermis—and a thicker layer—the dermis.
Physiologic barriers to infection that contribute to innate immunity include temperature, pH, and various soluble and cell associated molecules. Another important innate defense mechanism is the ingestion of extracellular particulate material by phagocytosis. Phagocytosis is one type of endocytosis, the general term for the uptake by a cell of material from its environment. In phagocytosis, a cell’s plasma membrane expands around the particulate material, which may include whole pathogenic microorganisms, to form large vesicles called phagosomes. Tissue damage caused by a wound or by an invading pathogenic microorganism induces a complex sequence of events collectively known as the inflammatory response.
Adaptive immunity is capable of recognizing and selectively eliminating specific foreign microorganisms and molecules (i.e., foreign antigens). Unlike innate immune responses, adaptive immune responses are not the same in all members of a species but are reactions to specific antigenic challenges. Adaptive immunity displays four characteristic attributes: Antigenic specificity, Diversity, immunologic memory and self/nonself recognition.
The antigenic specificity of the immune system permits it to distinguish subtle differences among antigens. Antibodies can distinguish between two protein molecules that differ in only a single amino acid. The immune system is capable of generating tremendous diversity in its recognition molecules, allowing it to recognize billions of unique structures on foreign antigens. Once the immune system has recognized and responded to an antigen, it exhibits immunologic memory; that is, a second encounter with the same antigen induces a heightened state of Immune reactivity. Because of this attribute, the immune system can confer life-long immunity to many infectious agents after an initial encounter. Finally, the immune system normally responds only to foreign antigens, indicating that it is capable of self/nonself recognition. The ability of the immune system to distinguish self from nonself and respond only to nonself molecules is essential, for, as described below, the outcome of an inappropriate response to self-molecules can be fatal. Adaptive immunity is not independent of innate immunity.
There are two types of Immunity Cell mediated immunity and Humoral Immunity. Cell mediated immunity is mediated by cells. It provides the defense against fungi, viruses, and bacteria. Antigen presenting cells are macrophages, dendritic cells and B cells. Helper T cells activate other T cells and B cells. Helper T cells has two types helper-1 (TH1) cells and helper-2 (TH2) cells.
Role of cytotoxic T cells is to directly destroy cells by release of toxic enzymes, destroys cancer cells and transplanted organ cells and destroys body’s own tissues that are infected. Role of suppressor T cells is to regulate t cells, suppress the activities of cytotoxic t cells and prevent killing of body's own cells. Role of memory T cells is to remain in lymph nodes and store memory of antigen to illicit a strong response.
In the fourth section of this lecture educators gives the introduction of Humoral Immunity. It is Antibody mediated immunity and it provides defese against Bacterial Infections. Role of Plasma cells is to Destroy antigens through antibodies (Ab). Role of memory B cells is to Store memory of antigens and Make Abs faster and more potent. Role of Helper T cells is Activation of more B lymphocytes, Proliferation of plasma cells and Production of antibodies.
A protein that is produced by B lymphocytes in response to the presence of an antigen is called Antibody. There are five types of antibodies IgA (Ig alpha), IgD (Ig delta), IgE (Ig epsilon), IgG (Ig gamma) and IgM (Ig mu).
Immune Dysfunction and Its Consequences
Sometimes the immune system fails to protect the host adequately or misdirects its activities to cause discomfort, debilitating disease, or even death. There are several common manifestations of immune dysfunction: Allergy and asthma, Graft rejection and graft-versus-host disease, Autoimmune disease and Immunodeficiency.
Allergy and asthma are results of inappropriate immune responses, often to common antigens such as plant pollen, food, or animal dander. Common allergic conditions are Food allergy, Allergic rhinitis, Brochial asthma and Urtcaria. Allergens are introduced by contact, Inhalation, Ingestion and injection.