The immune system is made up of a network of cells, tissues, and organs that work together to protect the body against infectious organisms and other invaders. The immune system is the body’s natural defense mechanism. The function of this system is to prevent or reduce the occurrence of infection. This is accomplished through the coordinated function of the body’s immune cells. The immune system is divided into two systems:

  • The innate response in a non-specific immune response that serves as the first line of defense against numerous germs and parasitic pathogens. Physical deterrents such as skin, chemical deterrents such as enzymes found in perspiration and saliva, and inflammatory reactions stimulated by immune cells encompass the innate immune system. The innate immune response is not specific to any pathogen. White blood cells involved in the innate immune response include macrophages, dendritic cells, and granulocytes (neutrophils, eosinophils, and basophils). These cells respond immediately to threats and are also involved in the activation of adaptive immune cells.
  • The adaptive response provides a specific defense mechanism in which immune cells respond to specific pathogens and provide protective immunity. Like innate immunity, adaptive immunity includes two components:
  • The humoral immune response or antibody‐mediated response protects against bacteria and viruses present in the fluids of the body.  B cells, of his system recognize organisms that are external to the body. B cells produce antibodies that recognize and bind to a specific antigen to identify it as an invader that needs to be terminated.
  • The cell mediated immune response protects against foreign organisms that have managed to infect body cells. It also protects the body from itself by controlling cancerous cells. White blood cells involved in cell mediated immunity include macrophagesnatural killer (NK) cells, and T cell lymphocytes. Unlike B cells, T cells dispose antigens via the production of proteins called T cell receptors (TCRs) that help them recognize a specific antigen. There are three classes of T cells that play specific roles in the destruction of antigens: Cytotoxic T cells (which directly terminate antigens), Helper T cells (which precipitate the production of antibodies by B cells), and Regulatory T cells (which suppress the response of B cells and other T cells).

Immune System in Disease

The immune system has an essential role in various diseases. Three known immune disorders are allergies, severe combined immunodeficiency (T and B cells are not present or functional), and HIV/AIDS (severe decrease in the number of Helper T cells). In cancer immunotherapy, the immune system’s function is dysfunctional and fails to identify tumors during the surveillance process. In cases involving autoimmune disease, the immune system attacks the body’s own normal tissues and cells. Examples of autoimmune disorders include rheumatoid arthritis (affects joints and tissues), and graves disease (affects the thyroid gland).

New techniques and technologies have led to an in-depth understanding of the various immune cells in the context of disease biology.

This understanding has paved the way for the development of novel drugs and diagnostics and an increased investment by pharmaceutical and biotechnology companies in immune-mediated disease research.

What are the cells of the immune system?

Cells of the immune system, known as white blood cells, are found in our bone marrow, lymph nodes, spleen, thymus, tonsils, and in the liver of embryos. When microorganisms, such as bacteria or viruses invade the body, non-specific defense mechanisms provide the first line of defense.

White blood cells or also known as leukocytes are blood components that protect the body from infectious agents. They play an important role in the immune system by identifying, destroying, and removing pathogens, damaged cells, cancer cells, and foreign matter from the body.

Leukocytes originate from bone marrow stem cells and circulate in blood and lymph fluid. Leukocytes can leave blood vessels to migrate to body tissues.

White blood cells are categorized by Granulocytes (with granules containing enzymes) and Agranulocytes (no granules)

This understanding has paved the way for the development of novel drugs and diagnostics and an increased investment by pharmaceutical and biotechnology companies in immune-mediated disease research.