Biol 537 Immunology Research Paper

The immune system is made up of several types of cells that work together to fight infections. Lymph cells (called lymphocytes) are the main type of cell in the adaptive immune system. There are 2 types of lymph cells: T cells and B cells. When B cells respond to an infection, they change into plasma cells. The plasma cells are found mainly in the bone marrow—the soft, inner part of some bones. The plasma cells

To fight of viruses, each of them have a special antibody formed to kill that particular virus. To be able to fight them, we need to have more antibodies, so our body produces antibodies to protect itself.

Cytotoxic T cells have receptors that allow them to connect with specific antigens and kill them to prevent an immune response to a virus. T helper cells have a surface protein called CD4 which aids in cell interaction and the secretion of cytokines.

Viruses are microscopic particles that invade and take over both eukaryotic and prokaryotic cells. They consist of two structures, which are the nucleic acid and capsid. The nucleic acid contains all genetic material in the form of DNA or RNA, and is enclosed in the capsid, which is the protein coating that helps the virus attach to and penetrate the host cell. In some cases, certain viruses have a membrane surrounding the capsid, called an envelope. This structure allows viruses to become more stealthy and protected. There are two cycles in which a virus can go into: lytic and lysogenic. The lytic cycle consists of the virus attaching to a cell, injecting its DNA, and creating more viruses, which proceed to destroy the host. On the other hand, the lysogenic cycle includes the virus attaching to the cell, injecting its DNA, which combines with the cell’s DNA in order for it to become provirus. Then, the provirus DNA may eventually switch to the lytic cycle and destroy the host.

“Humoral immunity is a type of immune response that depends on antibodies.” The response begins when a pathogen binds to a B cell. The B cell will engulf the pathogen and display a part of the antigen on its exterior. Once a T cell is exposed to the antigen-presenting B cell, the T cell will release proteins to activate the B cell. Now that the B cell is activated, it will produce antibodies to cause the pathogens to clump together. In the last stage of humoral immunity, phagocytes will engulf and destroy the pathogens.

Red and white blood cells are the two types of blood cells in the human body. Red blood cells transport oxygen around the body which is transferred through the bloodstream. It moves oxygen into the body and then removes it. They are absorbed through its haemoglobin.

Mature dendritic cells captures antigen and transports them to the lymph node, where they lose their properties and become immature dendritic cells that present antigens and activate naïve T cells.

The virus fuses with the cell’s plasma membrane. The capsid proteins are removed, releasing the viral proteins and RNA. Reverse transcriptase catalyzes the synthesis of a DNA strand complementary to the viral RNA. Reverse transcriptase catalyzes the synthesis of a second DNA strand complementary to the first. The double-stranded DNA is incorporated as a provirus into the cell’s DNA. Proviral genes are transcribed into RNA molecules, which serve as genomes for the next viral generation and as mRNAs for translation into viral proteins. The viral proteins include capsid proteins and reverse transcriptase (made in the cytosol) and envelope glycoproteins (made in the ER). Vesicles transport the glycoproteins from the ER to the cell’s plasma membrane. Capsids are assembled around viral genomes and reverse transcriptase molecules. New viruses bud off from the host cell.

The organs that make up the lymphatic and immune system are the tonsils, spleen, thymus gland, lymph nodes, and lymphatic vessels. White blood cells (leukocytes), red blood cells (erythrocytes), plasma, and platelets (thrombocytes) make up the blood. Lymphocytes are leukocytes (white blood cells) that help the body fight off diseases. Two types of lymphocytes are B cells and T cells. Lymphocytes recognize antigens, or foreign substances/matter, in the body. Lymphocytes are a classification of agranulocytes, or cells (-cytes) without (a-) granules (granul/o) in the cytoplasm. B cells are created from stem cells, which are located in the bone marrow. B cells respond to antigens by becoming plasma cells. These plasma cells then create antibodies. Memory B cells produce a stronger response with the next exposure to the antigen. B cells fight off infection and bacteria while T cells defend against viruses and cancer cells. A hormone created by the thymus gland called thymosin changes lymphocytes into T cells. The thymus gland is active when you are a child and slowly shrinks, as you get older. T cells bind to the antigens on the cells and directly attack them. T cells secrete lymphokines that increase T cell production and directly kill cells with antigens. There are three types of T cells: cytotoxic T cells, helper T cells, and memory T cells.

B cells are a third class of important immune system cells. They do not kill the invaders, but they do tell the killers who to kill. B cells produce specific protein called Antibodies. Each B cell watches out for a particular pathogen and when that pathogen arrives, e B cell begins to produce specific antibodies. Antibodies attach themselves to the specific pathogen so that the killers can recognise that these pathogens need to be destroyed.

Similar to T cells, each B cell also has its unique B-cell receptor that recognizes a particular antigen to be selected and eventually to become activated. The activated Th2 sends signal (interleukein – 4 B Cell Growth Factor) to the activated B cells to make more clones of the B cells. Once the B cell produces enough number of its clone, B cells start to express another receptor for Th2 to send another signal (B Cell Differentiation Factor or interLeukin-5). Once the B Cell Differentiation Factor stimulates B cells, they become plasma cells and start the production of IgM initially and then IgG. Some of B cells, however, become memory cells instead of becoming plasma cells. The amount of the antibody produced at the first response to the toxoid molecule is usually relatively low and it takes about 2 to 3 days (but often is longer, as long as weeks) for the B cells to be activated and to be differentiated into plasma cells. The first antibodies that encounter toxoid is, as mentioned previously, is IgM and a small amount of IgG. After about a week, however, the number of IgG supersedes IgM. Overtime, antibody level

The protective capsid helps the virus escape detection and destruction during the invasion of the host. When the virus reaches the target cell, biochemical reactions between the capsid and cell wall allow the virus to latch on and inject its genome into the cell’s interior. Once inside, the viral genetic material insinuates itself into the host’s DNA or RNA. In an efficient feat of natural bioengineering, the host cell’s genetic machinery now does the rest of the work for the virus. The cell, which had already been making copies of its own genome, now also replicates that of the virus. Coded within the viral material is the blueprint for making more copies of the viral genome. Further instructions command the production of capsids and directions for assembly of new viruses. After the host cell becomes engorged with viruses, it explodes, sending the new

After antigenic stimulation, the mature B cell are activated when interact with the T helper cell/antigen, then the B cell will proliferate into centroblasts in dark zone of the lymph node. Due to large amount of centroblasts is produced in a short time, the DNA will mutate including the germ line. This mutation rate is million fold faster than the spontaneous mutation rate compared to other gene, on average one or two times cell division will introduce one time mutation. This can generate one of the B cell produce suitable antibodies against the antigen. This process is called somatic hypermutation. Due to this mechanism till not yet be determined, in the future scientists will go deeply on this area.

They are located in areas, where antigens can enter the body, for example in the epithelium of the skin or the gastrointestinal tract. Dendritic cells catch antigens and transport them to the lymph nodes. There parts of these antigens are presented to the T lymphocytes, which then recognize the antigen. When antigens get through the epithelium, they are engulfed by macrophages, which are located in the tissue, and presented to the T cells. If pathogens get into lymphoid organs, they will also be captured by either dendritic cells or macrophages and presented to the T

One type of immunity include antibody immunity, which is a type of chemical warfare in the body. It works when pathogens enter tissues through a wound and are attacked by macrophages at the infection site. Then, antigens of the pathogen are displayed on the surface of the microphage, next helper T cells have their receptors bind to the antigen on the macrophage. B-cels then directly bind to the antigen and helper T-cells bind to the antigens on the B-cells. Next chemicals are released by the T cells cause clones of the plasma cells to be created by B cells. Lastly, 2000 antibodies are released per second into the blood by the plasma cell, and future invasions by the same pathogen can be easily felt with because memory B cells and antibodies remain in the blood. Another type of immunity is cellular immunity. This type of immunity works with the help of cytotoxic cells, or killer cells, that are stored in lymph nodes, spleen, and the tonsils. When they are released, cytotoxic cells secrete enzymes that directly kill the pathogens. Passive immunity occurs either when antibodies are shared between mother and child through the placenta or milk, or when antibodies are injected into the body from something that is already immune. Lastly, active immunity is used when antibodies are produced when a pathogen invades the body. After the antibodies are formed, the person can become immune to that specific pathogen. These pathogens can be introduced to the body either through disease