-What is the role of T cells? - What is the difference between helper T cells an

Question

-What is the role of T cells? - What is the difference between helper T cells and cytotoxic T cells? -What are MHC classes I and II molecules and what is their role? -How are T cells activated? -How do Helper T cells and Cytotoxic T cells function in adaptive immunity?
Need help with all parts, please help :) -What is the role of T cells? - What is the difference between helper T cells and cytotoxic T cells? -What are MHC classes I and II molecules and what is their role? -How are T cells activated? -How do Helper T cells and Cytotoxic T cells function in adaptive immunity?
Need help with all parts, please help :) - What is the difference between helper T cells and cytotoxic T cells? -What are MHC classes I and II molecules and what is their role? -How are T cells activated? -How do Helper T cells and Cytotoxic T cells function in adaptive immunity?
Need help with all parts, please help :)

Explanation / Answer

1- Role of T cells:- The activated T cells secrete various cytokines such as interleukin -2 (IL- 2) to promote differentation of both B cells and T cells. Interleukin- 2 provides and autocrine signal to induce repeated cell divisions for clonal expansions. T cells plays role in the regulation of bothe AMIS and CMIS.

2- Difference between helper T cells and cytotoxic T cells:-

helper T cells:- the cells have no phagocytic activity but are vital for immune system. They are essential in determining B cell antibody. Once activated the helper T cells divide rapidly and release cytokines to enhance or regulate immune response.

cytotoxic T cells:- These cells have phagocytic activity and migrate towards the site of infection. They play a major role in cell mediated immunity to destroy virally infected cells, tumour cells.

3- MHC classes I and II molecules and what is their role:- The MHC is a set of genes that code for cell surface glycoproteins. These glycoproteins mark the body cells as 'self' and are divided into two main classses: classI MHC and classII MHC. ClassI MHC are found on the surface of almost every cellof the body. ClassII MHC molecules are confined to a few specialized cell types such as macrophages, B- cells., and activated T- cells. The role or job of MHC molecule is to present an antigen to a T- cell. Each MHC- antigen combination forms a unique complex that is recognised by a specific antigen receptors on T- cells as 'self'.

4- T- cells activation:- Antigen presenting cells is necessary for activation of T -cells. Since it is absent on their surface resting macrophages and B -cells they fail to activate T -cells. Somtimes T -cells fail to respond even after interacting with the antigen. The non responsiveness of T -cells after interaction with MHC classII complex is known as "colonal anergy". This is due to the un availability of T -cells to undergo clonal expansion in the co stimulatory signal produced by the interaction of TCR, CD's complex on TH cells with B7 on antigen presenting cells. Apart drom this cytokines released by the antigen presenting cells aslo involve in the activation process. A series of membrane also changes in the development of new receptors suvh as highly affinity IL- 2 and gain of special function characters. Antigen interaction with T- cells provides the frist activating signal and interleukin- 1 secreting by antigen presenting cellserves as second signal for T -cell activation. With half an hour of activation a number of transcription factors are expressed by activated T -cells and release various cytokines within 1 to 2 hours of activation.

5-  Helper T cells and Cytotoxic T cells function in adaptive immunity:-

Helper T cells can stimulate B cells to produce antibodies that bind that specific antigen and immobilize it and preventing it from causing infection. Antibodies are specific for only one antigen. B cells must interact with Helper T to start antibody production. Once activated, memory cells are produced that insure that a more rapid and stronger immune response can be made upon re-exposure to the same pathogen. Memory helper T cells are labeled CD4+ CCR5+, to note that the chemokine receptor (CCR5) is present on the surface of the helper T -cell. These cells migrate and reside in the mucus membranes of our body.   Cytotoxic T cells kill infected cells and preventing these cells from producing more pathogen. Cytotoxic T- cells interact with Helper T- cells to regulate destruction of infected cells. Remember that the dendritic cells must activate CD4+ helper T- cells before our bodies can produce B cells secreting pathogen specific antibodies or cytotoxic T -cells to destroy infected cells.

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