Download to read offline
More Related Content
Similar to Cells of the Immune System (Sentinels of the Body's Defense)
Cells of the Immune System (Sentinels of the Body's Defense)
- 1. Cells of the ImmuneSystem Sentinels of the Body's Defense Presented by – Deepanshu Banyal (MAU23PBT010) Presented to – Dr Abhishek Awasthi Department of Biotechnology
- 2. Content Introduction tothe Immune System Cells of the Immune System Common Lymphoid Progenitor Common Myeloid Progenitor References
- 3. Introduction to theImmune System Complex network of cells, tissues, and organs that work together to protect the body against foreign invaders, such as pathogens (viruses, bacteria, fungi), toxins, and abnormal cells. The primary functions of the immune system are: 1. To recognize and respond to foreign substances or pathogens (immune recognition) 2. To neutralize and eliminate these threats (immune response) 3. To establish long-term protection against specific pathogens (immunological memory)
- 4. Cells of theImmune System The immune system is a defense system in a host consisting of widely distributed cells, tissues and organs that recognize foreign substance and microorganisms and acts to neutralize them. The cells present both specific and non- specific immunity are leukocytes (or white blood cells). Leukocytes include neutrophils, eosinophils, basophils, mast cells, monocytes and lymphocytes. All leukocytes arise from Hematopoietic Stem Cell (HSC). During hematopoiesis, HSC differentiates along one of two pathways, giving rise to either a Common Lymphoid Progenitor or a Common Myeloid Progenitor.
- 5. In humans, hematopoiesis beginsin the embryonic yolk sac during the first weeks of development and continue whole life – location changes to yolk sac (1st week) → liver (3rd week to 7th weeks of gestation) → bone marrow (whole life).
- 7. Common Lymphoid Progenitor Lymphocytes Small white blood cells which are responsible for much of the work of the Immune System. Lymphocytes can be divided into three classes: B cells, T cells and Natural Killer cells (NKC) . Mature lymphocytes all have a similar appearance. They are small cells with a deeply basophilic nucleus and scanty cytoplasm.
- 8. B Cells andT Cells T cells or T lymphocytes belong to a group of white blood cells and play a central role in Cell-mediated Immunity. While, B cells are lymphocytes that play a large role in the Humoral Immune Response. B cells is an essential component of the Adaptive Immune System. B cells spend their entire early life in the bone marrow. While the T cells, leave the bone marrow at an early age and travel to the thymus, where they mature.
- 9. The principalfunctions of B cells is to make antibodies against antigens, perform the role of antigen-presenting cells (APCs) and eventually develop into memory B cells after activation by antigen interaction. On the other hand, T cells constitutes 65-75% of blood lymphocytes. They can be distinguished from other lymphocytes by the presence of a T cell receptor (TCR) on the cell surface. Another key feature of B cells and T cells, includes the receptors it has in its surface. T cells recognize a linear sequence of amino acids whereas, B cells the spatial arrangement of proteins, nucleic acids, polyssacharides or lipids.
- 11. T Cells HelperT-Cell: assist other white blood cells in immunologic processes, including maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells and macrophages. Cytotoxic T-Cell: destroy virally infected cells and tumor cells, and are also implicated in transplant rejection. Regulatory T-Cell: formerly known as suppressor T cells, are crucial for the maintenance of immunological tolerance. Memory T-Cell: are a subset of antigen-specific T cells that persist long-term after an infection has resolved.
- 12. B Cells PlasmaB-Cells: are large B cells that have been exposed to antigen and produce and secrete large amounts of antibodies, which assist in the destruction of microbes by binding to them and making them easier targets for phagocytes and activation of the complement system. Memory B-Cells: are formed from activated B cells that are specific to the antigen encountered during the primary immune response. B1 Cells and B2 Cells Marginal B-Cells Follicular B-Cells
- 13. Natural Killer Cells These cells lack the marker molecules characteristic of B and T cells. They comprise about 10-15% of the lymphocytes of circulating blood. The role NK cells play is analogous to that of cytotoxic T cells in the vertebrate adaptive immune response. NK cells provide rapid responses to virally infected cells and respond to tumor formation, acting at around 3 days after infection. NK cells are unique, however, as they have the ability to recognize stressed cells in the absence of antibodies and MHC, allowing for a much faster immune reaction. They were named “natural killers” because of the initial notion that they do not require activation in order to kill cells that are missing “self” markers of major histocompatibility complex (MHC).
- 15. Common Myeloid Progenitor Monocytes These are mononuclear phagocytic leukocytes that circulate briefly in the bloodstream before migrating into the tissue where it becomes macrophages or dendritic cells. Monocytes circulate in the bloodstream for about 8 hours, during which they enlarge; then they migrate into the tissues and differentiate into specific tissue macrophages or dendritic cells.
- 16. Macrophages Macrophages arecells produced by the differentiation of monocytes in tissues. It function in both non-specific defense, Innate Immunity, as well as help initiate specific defense mechanisms, Adaptive Immunity, of vertebrate animals. Their role is to ”phagocytose” (engulf and then digest) cellular debris and pathogens, either as stationary or as mobile cells. They also stimulate lymphocytes and other immune cells to respond to pathogens. They are specialized phagocytic cells that attack foreign substances, infectious microbes and cancer cells through destruction and ingestion.
- 18. Dendritic Cells Dendriticcells are professional antigen-presenting cells that capture, process, and present antigens to T cells. They bridge innate and adaptive immunity, initiating and regulating immune responses against pathogens and cancer. Different subsets, including conventional and plasmacytoid dendritic cells, reside in tissues and lymphoid organs. Their maturation and migration to lymph nodes facilitate T cell activation and tailored immune responses.
- 20. Neutrophils Neutrophils arethe most abundant type of granulocytes and first responders of the innate immune system. They rapidly migrate to sites of infection or inflammation, guided by chemotactic signals. Neutrophils employ various mechanisms to eliminate pathogens, including phagocytosis, degranulation, and neutrophil extracellular traps (NETs). These short-lived cells play a crucial role in acute inflammatory responses and host defense. Dysregulation of neutrophil functions can contribute to autoimmune disorders and chronic inflammatory conditions.
- 22. Eosinophils These cellsare white blood cells that are one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. Along with mast cells, they also control mechanisms associated with allergy and asthma. They are granulocytes that develop during hematopoiesis in the bone marrow before migrating into blood.
- 23. Basophils The namecomes from the fact that these leukocytes are basophilic; they are susceptible to staining by basic dyes. Basophils contain large cytoplasmic granules which obscure the cell nucleus under the microscope. However, when unstained, the nucleus is visible and it usually has 2 lobes.
- 24. Mast Cells Theseare cells concentrated within the respiratory and gastrointestinal tracts, and within the deep layers of the skin. These cells release histamine upon encountering certain antigens, thereby triggering an allergic reaction. The mast cell is very similar in both appearance and function to the Basophil, a type of white blood cell.
- 25. Red Blood Cell It is also called “Erythrocytes” and has two functions: 1.) To pick up oxygen from the lungs and deliver it to tissues elsewhere. 2.) To pick up carbon dioxide from other tissues and unload it in the lungs. An erythrocyte is a disc-shaped cell with a thick rim and a thin sunken centre. RBCs are incapable of aerobic respiration, preventing them from consuming the oxygen they transport because they lose nearly all their inner cellular components during maturation.
- 27. Platelets Platelets aresmall fragments of bone marrow cells and are therefore not really classified as cells themselves. Platelets have the following functions: Secrete vasoconstrictors which constrict blood vessels, causing vascular spasms in broken blood vessels, Form temporary platelet plugs to stop bleeding, Secrete procoagulants (clotting factors) to promote blood clotting, Dissolve blood clots when they are no longer needed, Digest and destroy bacteria, Secrete chemicals that attract neutrophils and monocytes to sites of inflammation and Secrete growth factors to maintain the linings of blood vessels.
- 29. References Kono, H.,& Rock, K. L. (2008). How dying cells alert the immune system to danger. Nature Reviews Immunology, 8(4), 279-289. Kopitar-Jerala, N. (2006). The role of cystatins in cells of the immune system. FEBS letters, 580(27), 6295-6301. Hervas-Stubbs, S., Perez-Gracia, J. L., Rouzaut, A., Sanmamed, M. F., Le Bon, A., & Melero, I. (2011). Direct effects of type I interferons on cells of the immune system. Clinical Cancer Research, 17(9), 2619-2627. Lubbers, R., Van Essen, M. F., Van Kooten, C., & Trouw, L. A. (2017). Production of complement components by cells of the immune system. Clinical & Experimental Immunology, 188(2), 183-194. Delves, P. J., & Roitt, I. M. (2000). The immune system. New England journal of medicine, 343(1), 37-49.
- 30.