The immune system is a complicated biological body system that protects us from pathogenic organisms such as bacteria, viruses and fungi which has cells that are from the hematopoietic stem cell in the bone marrow. It includes white blood cells, chemicals and proteins like complement proteins and antibodies. The system is divided into two major parts that is the innate immunity system (non-specific) and the adaptive system (specific). The innate plays a vital role in the system as it is the primary defence mechanism whilst the adaptive immune system is the second line of defence. All the types of the immune system involve cellular and humoral components which carry out protective functions.
Cellular defences are used to differentiate whether an immune response is intervened by a certain type of cell. Cells such as the macrophages and the monocytes are involved with phagocytosis. These cells are all present in the myeloid lineage of the haematopoietic stem cells of the bone marrow. The stem cell is made up to two cells namely the myeloid progenitor and the lymphoid progenitor. The myeloid progenitor produces more dendritic, monocytes, neutrophils and basophils cells whereas the T and B cells are produced more in the lymphoid progenitor. Macrophages and dendritic cells play a vital role in the both types of immunity. These cells come from the mast cells and monocytes which are fixed tissues from the same cell as the circulating basophils. The B cells are found in the bone marrow and released into the lymphatic systems and blood. It develops into plasma cells and secretes antibodies. The T cells undergoes processes in the thymus where there are two types of cells being made, namely the CD4+ helper cells , and the CD8+ cytotoxic T cells. They attack antigens and release cytokines to control immune response. Furthermore, the dendritic and macrophage work as a bridge between the innate and the adaptive immunity system. Thus, they show antigens to immune competent T-cells that initiates immune responses.
Neutrophils are also granulocytes that are mainly found in the bloodstream and makeup seventy percent of the circulating leukocyte population. They respond quickly to inflammatory signals from infected tissues that are damaged and are bacterial infected. They go through the endothelium of the blood vessels and enter sites of inflammation through the process of chemotaxis. Factors of this process like the IL-8 and C5a take neutrophils from the blood and enter the area of inflammation. This cell recruits several effector mechanisms that fight against infection. It releases antimicrobial peptides and reactive oxygen species through a respiratory burst on to the bacteria and surrounding it to destroy it. As mentioned above it also uses phagocytosis to destroy the pathogen. Lastly, produces a number of pro-inﬂammatory cytokines such as IL-12, IFN-γ and TNF, which are involved in the instigation of subsequent immune responses.
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