List some ways to prevent rejection of a transplanted organ? Explain your answers.

In order to prevent rejection, we must firstly do a HLA Typing test. This blood test looks at proteins called human leukocytes antigens, which is also known as HLAs for short. This proteins is being found on almost every surface of every cells in the human body.
The recipient's HLA and the donor's HLA must be the same, so that there will not be any rejections when there is an organ transplant.
After an organ transplant, our body are still not being cured totally. The reason is because the organ might still undergo rejection in the future. So the only way to prevent this is to take medicine.
This type of medicine is able to decrease the ability of a patient's immunity, and therefore, it also helps in preventing the rejection. However, this drug is not very good. The reason is because when a preson take this drug, their immunity will become lower, and their immunity against infections will be more weaker, and therefore, they will get infection more easily.
Also, in order to be safe, it is better for us to get organs from our close relatives. The reason is because by using organs of the close relatives, the chances of rejection will be lower.
Before having a transplant, the donor and the patients must also be checked on their health conditions, and to see that whether the organ transplant is able to go on. Like for example, if a donor does not realise that he himself has AIDS disease, and he donate his organ to someone in need. The person receiving his organs will get infected with the disease too. Therefore, checking the health condition is very important too, as it also checks whether a person is suitable to transplant his organs or not.
Also, it is more safer to get human donors rather to get animal donors. The reason is because humans and animals are genetically different, and if animal organs are being transplanted onto humans, the animal's genes and human's genes are different, and also, the immunity of that particular animal and humans are different, therefore, it might have more higher possibility of having rejections, therefore it is safer to get human organ donors.

MHC

a) In the MHC Class I, the antigenic proteins which enters the Antigen Presenting Cell will firstly undergo degradation by a protein called protease. After degrading, it will be transported by TAP, and then the antigenic peptide will be loaded onto the Class I MHC Molecule. The MHC then move to the cell surface and display the antigenic peptide. The T killer cell bind onto the MHC molecule, and the killer T cell will then be activated, and then it will be able to kill the infectious foreign particles directly.

b) In the MHC Class II, when the antigens enter the Antigen Presenting Cell, phagosomes are formed, and the phagosomes containing the antigens are merged with the lysosome. Then, the MHC class II molecules migrate into the phagolysosome where the antigen is being degraded, and the invariant chain is removed for peptide binding. The Class II MHC molecule then moves to the cell surface, and present the antigenic peptide to the helper T-cell, and it will help to activate immune cells to fight against the foreign infectious particles.

Immunology - Complement System C1 to C9

In Complement System, there are different types of proteins in the complement system. These proteins are named from C1 to C9.

Firstly, the antibody will bind onto the infectious particle. After that, C1 will attached onto the antibody.

After attaching onto the antibody, C1 will then be activated, and then it will split to form C2a and C4b fragments.

When these 2 fragments joined together, it will then form the C3 convertase.

C3 convertase is able to cleave C3 into C3a and C3b.

C3a is able to cleave C5 into C5a and C5b.

C5b, C6, C7, C8, and C9 are able to attach itself onto the infectious cell membrane, and therefore opening a hole on the membrane, and allowing the infectious cell content to lysate, and it leads to self-destruct. This process is known as MAC, which is known as Membrane Attacking Complex.

C3b is able to attach itself to the infectious cell, and therefore it will help in opsonisation, and it will then undergo phagocytosis.

Clonal Selection (School Revision) Immunology

Clonal Selection is the process of forming new antibodies. When there is a new antigen(foreign infectious particles) invading our body, it will trigger the immune system. The T-cell will then activate the B-cell. After the B-cells are being activated, it will start to undergo a few cell divisions. After going through many cell divisions, it will form many memory cells and plasma cells.

The functions of the memory cell is to store the information of the specific antibody that has the immunity against the new antigens. If there are memory cells, the immune system will then be able to produce the specific antibody that has immunity to the new antigens.

The functions of the plasma cells is to produce antibodies to fight against the new foreign antigens.

After we recovered from the disease, the memory cell still remains in our body. Therefore if we infected the same disease again, we still have the memory cell which are present in our body, therefore, the plasma cell will produce the same antibody to fight against the disease. Therefore we can have immunity on the second time we infected the same disease.