Immunity is derived from the Latin word "immunis," which originally meant "exempt from taxation" and also implied "free from disease." Immunology is the science that studies the immune responsiveness of organisms to antigenic substances and its methods. In simple terms, immunity is a physiological function of the body to recognize "self" and "non-self" antigens, form natural immune tolerance to self-antigens, and produce a rejection effect on "non-self" antigens. Under normal circumstances, this physiological function is beneficial to the body, generating immune protective effects such as anti-infection and anti-tumor to maintain the physiological balance and stability of the body. Under certain conditions, when the immune function is disordered, it can also produce harmful reactions and outcomes to the body, such as triggering hypersensitivity reactions, autoimmune diseases, and tumors.

 

Physical Barrier (Immunological Barrier)

 

The physical barrier is referred to as the body's "first line of defense" and is an important component in exerting non-specific immune functions. Healthy and intact skin and mucous membranes envelop the body, mechanically blocking the invasion of pathogenic microorganisms and other antigenic foreign bodies; nasal hairs in the nostrils, mucus on the surface of the respiratory tract mucosa, and cilia can all block and expel the invasion of antigenic foreign bodies. The skin and mucous membranes can frequently secrete bactericidal substances. Lactic acid secreted by the sweat glands of the skin and fatty acids secreted by the sebaceous glands are acidic, which is unfavorable for the growth of pathogenic bacteria; lysozyme in saliva, tears, milk, and respiratory tract secretions can dissolve gram-positive bacteria. Hydrochloric acid in gastric juice also has a strong bactericidal ability. In addition, the normal flora growing on the skin, mucous membranes, and body cavities that are connected to the outside world maintain a mutually dependent and mutually restrictive balance with the human body. The normal flora effectively kills the invasion of pathogenic bacteria through the metabolic products secreted by their growth and metabolism.

 

Innate Immune System

 

Any "invader" that penetrates the physical barrier composed of skin or mucous membranes will encounter the innate immune system—the body's second line of defense. Innate immunity is the natural immune defense function formed by the body during the process of phylogenetic development and evolution, that is, the non-specific defense function that is already present after birth, also known as non-specific immunity. It is a series of defense mechanisms formed by organisms during the long process of evolution. Innate immunity is the body's physiological rejection response to a variety of antigenic substances. In contrast, adaptive immunity refers to a series of defense functions produced after birth through contact with antigenic substances.

 

The main innate immune cells include phagocytes, which are divided into two categories: neutrophils and mononuclear phagocytes; there are also dendritic cells (widely distributed in tissues and organs throughout the body, named for their many branched protrusions); natural killer cells (originating from bone marrow lymphoid stem cells); in addition, there are other innate immune cells including: NKT cells, γδT cells, B-1 cells, mast cells, eosinophils, and basophils.

Figure 1 Phagocytes engulfing Mycobacterium tuberculosis

 

Adaptive Immunity

 

Specific immunity, also known as acquired immunity or adaptive immunity, is targeted against a single pathogen. It is the body's resistance to infection acquired through postnatal infection (recovery or asymptomatic infection) or artificial vaccination (vaccines, toxoids, immune globulins, etc.). It is generally formed after stimulation by microbial and other antigenic substances (immune globulins, immune lymphocytes) and can react specifically with the antigen.

 

In the 1790s, Edward Jenner discovered in his medical practice that cowpox was a disease very similar to smallpox in symptoms, but much milder than smallpox, with no one dying from cowpox and no pockmarks left behind. The most important point is that patients who had cowpox would never contract smallpox again for life. Based on this discovery, with the consent of the locals, he inoculated the cowpox virus into an eight-year-old boy named James Phipps. Soon Phipps contracted cowpox. Two months later, after the cowpox symptoms had completely disappeared, Jenner inoculated him with the smallpox virus again, and as observed, Phipps showed no symptoms of smallpox infection. This was a great discovery and the most notable contribution of Jenner. Soon he wrote a series of papers on the research of the cowpox vaccine, and his views were also recognized by many medical professionals, promoting this smallpox vaccine to the world.

 

Antibodies and B Cells

 

Immunologists ultimately determined that the immunity against smallpox originated from some special proteins circulating in the blood of immune individuals, which were named antibodies, and the substances that induced the production of these antibodies were called antigens. Antibodies can be divided into five classes: IgM, IgG, IgA, IgE, and IgD. Each type of antibody is produced by B cells, which are a type of white blood cell born in the bone marrow and can later mature into plasma cells, also known as "antibody factories."

 

Catalog Number	Product Name	Specification
abs520012	Mouse IL-13 ELISA Kit	96T
abs552001	Mouse IL-1α ELISA Kit	96T
abs551025	Human IFN-α ELISA Kit	96T
abs510002	Human IL-1 beta ELISA Kit	96T
abs510005	Human IL-10 ELISA Kit	96T

 

 

Absin Bioscience Inc. Email: worldwide@absin.cn

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