Compare & Contrast the recognition of Antigens by B & T Lymphocytes

The recognition of antigens varies amongst cells, as all cells are different in many ways, one of them would be how they work. There are two types, which are B and T lymphocytes, these 2 in many ways are the same in the way they recognize antigens, however, are different to each other dramatically. Antigens are able to generate antibodies. Antigens are mostly a protein or a polysaccharide. There are 3 types of antigens, these would be exogenous, endogenous and auto antigens. Exogenous are antibodies that have entered the body from outside, for instance when we inhale, endogenous is when the antigens have been a product from a cell and lastly autogenous antigens are only produced if the patient is suffering from disease however this type of antigen is not the target of the human immune system.

B cell lymphocytes are able to make antibodies, also are able to detect and recognize and also respond to antigens. B Lymphocytes, secrete antibodies which help detect infection in the human body. We can easily tell if we have B lymphocyte cells, if your body didn’t contain B cells, then you would get ill very quickly since your body could not detect infections.

B Cell Lymphocytes originate on the bone marrow, which then migrate to the secondary lymphoid tissue. The role of B cells in the Human body is the response to antigens, as defense to the body is crucial; therefore the B cells keep the human body protected from Bacteria, etc.

The way in which B cells recognize antigens are by the antibody surface receptors, below is an example of an antibody surface:

(Source taken from MICR 1025 Lectures)

B cell Lymphocytes also recognize antigens via molecular complementation; lymphocytes only make 1 shape of a receptor and can ...

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The way in which B cells recognize antigens are by the antibody surface receptors, below is an example of an antibody surface:

(Source taken from MICR 1025 Lectures)

B cell Lymphocytes also recognize antigens via molecular complementation; lymphocytes only make 1 shape of a receptor and can only recognize one shape of epitopes. The lymphocytes possess protein surface receptors that recognize epitopes.

The response to antigens by B cell lymphocytes is the antigen is transported to the B cell lymphoid tissue, threw a flow of lypmh. Plasma cells are also found in the lymphoid tissue, due to the recognition, this stimulates the formation of the plasma cells.

On the other hand T cell receptors, work in a slightly different way, as the B cell lymphocyte uses surface receptors to detect and recognize antigens, T cell lymphocytes, recognize antigens by T cell receptors. The process in which antigen is recognized by the receptor, is that antigen is presented to T cell by a 2nd cell, this 2nd cell function as an antigen presenting cell. This is when Antigen is presented as peptide fragment by MHC molecules, the MHC molecules are expressed on the cell surface of a 2nd cell, which is defined as an antigen presenting cell. Antigen is presented by MHC molecules, on the APC cell surface. There are 2 types of MHC molecules, these are class 1 and class 2. Class 1 MHC molecules are expressed by all nucleated cells and present peptides from antigen produced from cells to CD8+ T cells, whereas Class 2 MHC molecules are expressed by dendritic cells, B cells and macrophages present peptides from exogenous proteins to CD4+ T cells. The dendtritic cells take up the antigen and transport antigen to the lymphoid tissue.

The diagram below shows the antigen recognition by T cell lymphocytes:

(Source taken from MICR 1025 lecture notes)

T cells are also involved in the overall regulation of immune responses, when antigens are inside or even associated with other cells in the body, and being this reason, the T cell lymphocytes cannot recognise free antigens, because the antigen is presented by the presenting cell, this ensures T cell response is directed infected cells.

B & T lymphocytes differ to each other as, T cell lymphocytes use MHC molecules to present different types of T cells, as MHC class 1 present antigen to only CD8+ cells and MHC class 2 present antigen to CD4+ cells therefore making T cells being restricted in the ways they recognise antigens, being more precise, T cells can only can only recognise epitopes of antigen which is presented to them on the surface of the cell using the 2 classes of MHC molecules, Whereas B cells can recognise antigen via the surface receptor, making them able to recognise any antigen.

However, B cells use a native epitope shape that is detected whereas the T cells use a complex MHC molecules process to detect epitopes. However, T cell lymphocytes have a similar structure to an antibody. A major difference would be that B cells respond to any chemical, however T cell lymphocytes respond to only peptide epitope 8 to 10 amino acids, Therefore B cells only being able to recognise surface exposed shapes.

The main similarity being between the 2 is that they can both recognize some kind of antigen, but use different methods in order to recognize. However, B & T lymphocyte, collaborate in the humoral immune response system, the CD4+ cells help divide and differentiate into antibody producing plasma cells. B & T Lymphocytes recognize the same antigen, however, different epitope. If there is no T cell receptor to help, then eventually the B cells will die by adaptosis, therefore the response to self antigen is prevented.

The mechanism involved in the collaboration between the 2 is very complex as CD4+ T-cells are specific to antigen, which are needed to help B-cell specific to the same antigen.

Overall, lymphocytes are immune cells which can recognize and respond to antigen, the 2 types of lymphocytes can collaborate, by using each of their unique ways to detect antigens. However they differ when they are on their own, being totally different to the way in which they recognize and respond to antigens, but B cells being less complicated in the way it works compared to T cells which Use the MHC molecules, but both are essential tools of the Human Immune system.