The immune system consists mainly of two types of immunity, the cellular immunity which includes of the different types of cells and the humoral immunity which consists of the antibodies and the cells producing them whenever a harmful organism enters our body. Our immune system can sense it and destroys it by different mechanism this is known as the sensitivity of our immune system. However, it defends typically us against infections, our immune system can get excessively sensitive against non-harmful things like dust pollen, medicines and many food substances this excessive activity of our immune system leads to local and systemic symptoms that can range from harmless itching to severe conditions like hypotensive shock and laryngospasm this excessive activity of our immune system to seemingly harmful antigens is known as hypersensitivity.

Types of hypersensitivity reactions

There are of four types dye one to type for which differ from each other as different components of the immune system are involved in each of them. Allergies are a classic example of the type 1 hypersensitivity reaction, which can be allergies to foods like peanuts, eggs, fish or allergies to dust and pollen. Bronchial asthma is also an example of type 1 hypersensitivity reaction. A person develops dust or pollen allergy the first phase of type 1 reaction involves sensitization this sensitization is to the antigen which refers to dust or pollen, in this case, this is the phase when the person has not yet developed hypersensitivity to the allergen when the person is exposed to the dust or pollen, it enters the body through two main routes, the respiratory membrane of lungs and the skin at both these places we have specialized cells known as the antigen present in cells. In the lungs, we have the pulmonary antigen present in cells, and in the skin, we have the Langerhans cells.


The T cells and B cells

These cells capture the minute antigens that are present on the dust or pollen, and they take these antigens to the T cells. To be exact, the naive cd4 T cells when exposed to these antigens become mature and are now known as mature cd4 T cells. These T cells produce a lot of chemicals like interleukin 4, interleukin 5, interleukin 13, and many more. Still, in the sensitization phase, the most critical cytokine is interleukin four which acts on P lymphocytes. The antibodies are produced by b-cells and the type of antibodies produced is the class of antibodies whether it be IgA IgG or IgM this interleukin 4 acts on B cells and leads to a phenomenon known as class switching which essentially means that the interleukin 4 makes a B cell to switch the class of antibodies that they are producing to immunoglobulin E.


Allergies involve a phase of sensitization in which the allergen enters the body for the first time, and our immune system forms a memory of this illusion the period of reaction begins when the allergen enters the body again it is quickly recognized by the IgE antibodies bound to mast cells which signal these cells to release vast amounts of chemicals.


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