Cellular Immunity - Adaptive Immunity part 1, Animation
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- Опубликовано: 27 окт 2019
- (USMLE topics) Steps of Cellular Immunity; Types of Cells Involved.
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The major players of cellular immunity are T-lymphocytes. They develop in the thymus, for which they are named. During the process of maturation, billions of variations of T-cells are formed, each carrying a unique surface protein, called T-cell receptor, TCR. In addition, a population of T-cells, called helper T-cells, also has a receptor named CD4; while a second population, of cytotoxic T-cells, carries CD8 receptor. In the process of development, T-cells also learn to not react to the body’s own antigens; those that react to self-molecules are eliminated. Mature T-cells then migrate to lymph nodes and other lymphoid tissues, where they await exposure to pathogens.
Basically, specific immunity relies on the invading pathogen finding a match among these billions of T-cell variations. Only the ones that can bind to the pathogen, are selectively activated. T-cells, however, cannot bind free-floating pathogens. They can only bind to pieces of the pathogen bound to a certain host molecule called major histocompatibility complex, or MHC, on the surface of so-called “antigen-presenting cells”. There are two classes of MHC:
- MHC class I molecules are expressed by all nucleated cells of the body. These molecules are constantly produced in the cytoplasm and, on their way to the cell membrane, pick up pieces of peptides and display them on the cell surface. If a cell is infected by a virus or is cancerous, a foreign or an abnormal antigen is displayed; and the cell can bind and activate a matching T-cell. MHC-I only binds CD8 receptor, thus activating only cytotoxic T-cells.
- MHC class II molecules occur exclusively on professional antigen-presenting cells, of which dendritic cells are most effective. Resident dendritic cells on the site of infection ingest pathogens and display them on MHC-II molecules on their surface. These dendritic cells then migrate to the nearest lymph node, and present the antigens to a matching T-helper cell, whose CD4 receptor binds to MHC-II.
Activation of T-cells requires a second binding between the two cells. This is the verification step, a safeguard mechanism serves to prevent the immune system from overreacting.
Once activated, T-cells undergo repeated cycles of mitosis in clonal expansion. This process produces clones of identical cytotoxic and helper T-cells, both of which are specific to the pathogen. Some of these cells differentiate into effector cells, other become memory cells.
Most effector T-cells leave the lymph node for the bloodstream and are delivered to the site of infection, where they carry out immune attack against the pathogen. Helper T-cells produce interleukins which help with the activation of cytotoxic T-cells, B cells, and other immune cells. With such diverse functions, helper T-cells are central to adaptive immunity. Cytotoxic T-cells are the main actors of cellular immunity. They release toxins and directly kill infected or cancerous host cells.
While effector cells die during or shortly after the infection, memory cells live for much longer periods of time. Some of them remain in lymph nodes, while other circulate the blood or migrate to peripheral tissues. Memory T-cells are also more numerous than the original naïve T-cells. Upon reexposure to the same pathogen, they can mount a much faster immune response, destroying the pathogen so quickly that no signs of illness are noticeable.
There is also a third T-cell population - regulatory, or suppressor T-cells, whose role is to dampen the immune response when it’s no longer needed.
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Your videos present information in an easy to understand format. Can you please make a video on Autoimmunity and also a video on Scleroderma? With many thanks for your excellent work.
Hats off I being a medico read lot of books and saw videos about immunity still I had doubts now it is cleared. Thank u so much
Great as usual❤️, keep diving on the ocean of medicine 🌊🌊.
Well done and exquisitely explained,thanks
This was one of the videos I requested a time ago! Whowww!!! Very wel done as usual indeed. 🎈👌 Looking forward to the next part.
Brilliant.!! And i have watcjed alot of videos on this
thanks alot .most clear explaination ever
Very helpful and explained very well. Thank you.
I like this video. It really helped me to understand cellular immunity.
awesome...
Most clear explanation ever.....thanks
Best one ive seen
Just wao. U just explained it so nicely that I felt that I was watching it physically 😌.
Such a great lecture
Thank you ❤❤❤.
Thank you for this video
oomg amazing thank youu so much 💜💜💜💜💜💙💙
Can you do the immune videos in further detail please? Like immense extreme detail and go over all the cells and mechanisms and aspects of the human immune system please
I think I will owe my graduation to this channel!
nice presentation.
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Much appreciation....❤❤
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Wow. Thank you so much.
You're very welcome!
How does the adaptive immune system produce a wide range of specific
receptors to effectively fight against foreign antigens while preventing the
attack on healthy tissues, and what mechanisms are involved in distinguishing
between self and non-self-antigens?
U made easy 👍❤️
What are the limitations of innate immunity in providing long-term protection against infectious agents, and how can these limitations be overcome to develop more effective strategies for preventing and treating infections?
This one cleared my doubt..... Thanks❤❤
Happy to help!
Good job Keep it up
But change background (black) color to other colors!!
Cool
Very helpfull
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You are very welcome!
Bahar çiftçi ❤😍👍
Great video
SDMMCITE!
Whose teacher made them watch this xd
,,👍👍
Nidhi Pangtey 414B
Nekadar fiyat
Bravoo but I didn't get it wet 😭😭