L. Pneumophila Essay

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

“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.

a. This function is mediated by T cells and B cells (memory cells) in our body via adaptive immunity. The adaptive immune system evolved in early vertebrates and allows for a stronger immune response as well as immunological memory, where each pathogen is “remembered” by a signature antigen. The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by memory cells. Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. So basically killer T cells will identify antigens present on foreign cells. These antigens are not found in any of the cells inside our body. Therefore, T cells will identify them and kill them.

The developmental routes for these cells are very complex and unique but there are similarities. B-cells produce antibodies to bind onto foreign bodies that have invaded the host organism; this allows cells such as cytotoxic T-cells will then destroy the infected cell/structure. On the other hand, T-cells such as T-helper cells that secrete cytokines to control immune responses and cytotoxic T-cells that destroy pathogenic cells and structures.

Class I MHC: there would be a chance the mouse would be susceptible to viruses. The Class I MHC functions by showing pieces of proteins from inside of the cell to the T Cells. If the mouse Class I MHC does not work then the unhealthy cells, viruses and, will be ignored as opposed to the healthy cells just being ignored.

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.

Sufficient stimulus by danger signals causes dendritic cells to become fully mature. This causes them to express signaling molecules that indicate the antigens they present were found in a dangerous environment. Mature dendritic cells promote immune reactions to

After development, each T cells have a unique form of T- cell receptor (TCR) which cannot identify the antigenic peptides directly, thus representing antigen specialized presenting cells (APC) such as dendritic cells (DCs) are required. DCs have the ability of processing the antigen into peptide to be presented by MHC molecules and they can migrate into the secondary lymphoid organs as well.

Some T lymphocytes (T cells), unlike B cells are able to attack targeted antigens directly and neutralise their effect on the body. Some send chemical messages to the rest of the immune system which help produce effective defences against the bacteria or virus, and some T cells even help B cells produce antibodies.

Dendritic cells are antigen presenting cells that stimulate the adaptive immune response by presenting antigens to the T cells. They are derived from hematopoietic bone marrow progenitor cells as immature dendritic cells. These immature dendritic cells have pattern recognition receptors like toll like receptors that recognize specific chemical structures of foreign antigens or non-self-antigens. Once the immature dendritic cells recognize foreign molecules they drain to the lymph nodes as mature dendritic cells and present these antigens in form of a peptide-major histocompatibility complex to naïve T and B cells for activation of the

This includes specific and non-specific action. Non-specific immunity includes phagocytosis (Figure 3). This is a process in which a phagocyte with specific receptor will bind to a pathogen with a complementary receptor, this causes the membrane of the phagocyte to wrap around the pathogen, engulfing it to create a phagosome6. A lysosome then fuses with the phagosome and secretes enzymes to hydrolyse the pathogen into peptide chains7. The peptide chains leave the phagosome and join the genes presented on the outside of the membrane of the phagcyte to create a MHC type 2 (major histocompatibility complex).7 The MHC allows specific parts of the immune system to activate.7 The non-specific immune system is important as it prevents the need for the specific immune system which requires more cells and uses more

The adaptive immune response is antigen-specific and requires the recognition of specific “non-self” antigens during a process called antigen presentation. Antigen specificity allows for the generation of responses that are tailored to specific pathogens or pathogen-infected cells. The ability to mount these tailored responses is maintained in the body by "memory cells". Should a pathogen infect the body more than once, these specific memory cells are used to quickly eliminate it. so basically killer T cells will identify antigens present on foreign cells. These antigens are not found in any of the cells inside our body. So T cells will identify them and kill them.

If a pathogen breaches barriers: innate immune response result into an immediate effect of non- specific response. All Innate immune systems derived from plants and animals, when a pathogen evades the innate response, a third layer of protection is possessed by vertebrates in which activation of adaptive immune system takes place. The immune system response adopts itself within an infection and pathogen recognition is improved. As a result of the improved response, its then retains itself when the pathogen is eliminated in form of an immunological memory and allows the adaptive immune system to mount faster and stronger when pathogen is encountered each time.

The interaction of CD8+ T cells with peptide-MHC complexes (pMHCs) is a key event in the development of cell-mediated immunity (Grakoui, 1999). MHC class I (MHC-I) molecules typically present 8-11 aa peptides derived predominantly from proteasomal degradation of intracellular proteins, either self-peptides or infection-derived antigens (Blum, Wearsch, & Cresswell, 2013). T cell receptors (TCRs) from CD8+ T cells bind antigenic pMHC molecules, triggering a downstream signaling cascade that leads to T cell activation, differentiation, and ultimately to cytolysis of target cells presenting the same epitope (Hennecke & Wiley, 2001). Vaccines and immunotherapies for the treatment of infection and cancer seek to incorporate cytotoxic T cell

The next cells are the T cells. There are many different types of T-cells. One is the Killer T-cell. They can recognize invaders with feelers on the outside of the cell and if the cell is infected, it can destroy the cell. Another type is the helper T-cell. The helper t-cell functions more as support. It matures B-cells and tells them to make antibodies by secreting a protein. A helper t-cell also activates the killer t-cell. The last major t-cell is the memory t-cell. If you get sick, the memory t-cell will remember the antigen and will the immune system be able to defeat the same disease faster. The next cell is the Natural Killer Cell. These cells are lymphocytes that destroy viruses by releasing a protein that makes the affected cell “program” itself for death. The process it destroys itself is called apoptosis. (Kidshealth.org)