The Human Body: The Innate Immune System

The human body is made up of complicated physiological processes, one of them being the process of transporting blood around the body by a system known as the circulatory system. This system carries blood around the body from the heart to the organs, tissues and cells of the body. Blood is made up of blood cells, namely erythrocytes, thrombocytes and leucocytes – in an extracellular matrix called plasma, which makes up approximately 55% of the blood. It is essential that blood is transported to the organs and systems of the body in order for these systems to function. The fluid is transported through blood vessels known as arteries, veins and capillaries in a succession starting and ending at the heart.

Physiology:

The short term immune response is known as the Innate Immune System and the long term is known as the Adaptive Immune Response. Monocytes and macrophages, primarily involved in atherosclerosis, are part of the innate immune response.

Macrophages have two main functions. They can act as phagocytes that engulf foreign particles or as antigen presenting cells. They receive signals in order to be activated. One of these signals is a cytokine known as interferon gamma (IFN-γ) secreted mainly by T helper cells. When LDL is deposited, macrophages are activated and the number of MHC class II molecules displayed on their surfaces is increased. When they engulf the LDL, it is broken down and presented to the T helper cells along with the MHC class II molecules for destruction and they are now seen as antigen presenting

The binding of C3b to the unwanted, oxidised LDL allows for the formation of C5a and C3a which chemotactically attracts and helps recruits macrophages and monocytes to the target site (endothelial wall) thereby causing an increase in the phagocytosis of LDL causing inflammation and the production of foam cells.

2) In addition, the protein C3b opsonises the oxidised LDL, thereby leading to the binding of complement receptors on both macrophages and monocytes and resulting in the phagocytosis of the LDL forming foam cells followed by antigen presentation. Molecular Medicine was used to help understand the function of the immune system’s macrophages and monocytes in atherosclerosis and their signalling pathways. Histology will show the structures and functions involved in atherosclerosis.

Histology:

Regarding atherosclerosis, there are two cells which are mainly involved in the process: the simple squamous epithelium of the endothelial wall that is damaged as well as monocytes which are precursors of resident macrophages both responsible for the immune