Innate Characteristics & Terminology

• Immunology involves the study of the body's defense against foreign substances that may cause harm.
• Immunity: resistance to infectious disease and foreign materials.
• The immune system refers to the body’s collection of cells and tissues that identify and destroy foreign invaders or abnormal tissues before they can harm the body.

Self vs Non-Self

• "Self" material is a normal component of the body.
• "Non-Self" material is not native to the body; it is foreign.

Innate vs Adaptive Immunity

• Innate immunity is a native or natural system present from birth.
• Adaptive immunity is acquired or specific.

Immune Response

• Immune Response: the coordinated reactions of the cells of the immune system to a pathogen.
• An antigen is any cell or molecule recognized by the immune system as foreign.
• Antigens bind to antibodies or T cell receptions with high affinity.
• Small molecules in the environment, bacterial, viral or any microbial surface proteins, and abnormal human tissue can all work as forms of antigens.

Lymphocytes and Immune Responses

• Lymphocytes are cells found in the blood, lymphoid tissues, and most organs that express receptors for specific antigens and mediate immune responses.
• Lymphocytes include B cells and T cells.
• B cells are B lymphocytes.
• T cells are T lymphocytes.
• When B and T cells become activated, they divide and mature into effector cells.
• Effector Cells: cells capable of fighting microbes.
• Mature B cells are called plasma cells, which secrete antibodies.
• Mature T cells are called effector T cells.
• Effector T cells help leukocytes, e.g., helper T cells/Th cells, and kill ingested microbes or directly kill infected cells via Killer T cells/CTLs, and cytotoxic T lymphocytes

Antibodies

• Antibodies, also called Immunoglobulins
• Glycoprotein molecules produced by Plasma cells.
• Assist in binding antigens with high affinity and therefore eliminate those antigens.

Cell Signaling

• Cell signaling refers to communication among cells of the immune system via the use of cell signaling.
• Cells of the immune system communicate directly by means of their surface molecules, or indirectly by releasing messenger molecules, cytokines.
• Cytokines are secreted proteins that work as mediators of immune and inflammatory reactions.
• Cytokines provide a mechanism for cells of the immune system to communicate and coordinate a response.
• Cytokines include: Chemokines, Interferons, Interleukins, Lymphokines, Tumor Necrosis Factor (TNF).

Major Histocompatibility Complex (MHC)

• The major histocompatibility complex (MHC) consists of cell-surface proteins coded for by the MHC genes.
• In humans, the MHC is called the human leukocyte antigen (HLA) complex.
• MHC molecules are important components of the immune system because they allow T lymphocytes to detect cells that have ingested infectious microorganisms.
• There are two types of MHC.

Humoral vs Cell Mediated Immunity

• Humoral immunity: a type of adaptive immunity that is mediated by B lymphocytes which become plasma cells when activated and produce antibodies.
• Humoral immunity is the main mechanism for defending mainly against extracellular microbes and their toxins.
• Adaptive immunity involves production of antibody molecules, and is mediated by B-lymphocytes
• Cell-mediated immunity: a type of adaptive immunity mediated by T lymphocytes
• Cell-mediated immunity is the main defense mechanism against microbes that survive within phagocytes (intracellular microbes).
• Cell-mediated immunity involves the production of cytotoxic T-lymphocytes and is mediated by T-lymphocytes.

Macrophages and Monocytes

• Macrophages are large immune cells found in tissue that destroy pathogens, while Monocytes are large immune cells found in blood that destroy pathogens.
• When monocytes move to tissue, they become macrophage.

The Immune System

• The Immune System is a collection of cells, tissues and molecules designed to produce a coordinated response due to the entrance of foreign substances or antigens into the body.
• The immune system is divided into two groups: innate, native or natural and Adaptive acquired or specific.
• The immune system is a "team effort," involving many different players, which can be divided into two groups: members of the innate immune system, and the adaptive immune system.
• Both innate and adaptive immune systems work together to provide a powerful defense against invaders.
• Innate immunity refers to antigen-nonspecific defense mechanisms that a host uses immediately or within several hours after exposure to almost any antigen.
• The immunity is something one is born with.
• Innate immunity provides the initial response, and is the first line of defense by the body to eliminate microbes and prevent infection.
• Innate immunity does not recognize every possible antigen.
• Instead, it is designed to recognize few structures that are present in many different microorganisms.
• These structures are called pathogen-associated molecular patterns.
• Most body defense cells have pattern-recognition receptors for the common pathogen-associated molecular patterns.
• There is an immediate response against the invading microorganism.
• The innate immune responses involve phagocytic cells, neutrophils, monocytes, macrophages, cells that release mediators basophils, mast cells, and eosinophils, natural killer cells NK cells, molecules, complement proteins, and cytokines
• Adaptive Acquired Immunity refers to antigen-specific defense mechanisms that take several days to become protective, reacts to and removes specific antigen
• Adaptive immunity is something one develops throughout his life.
• The body recognizes an antigen as foreign when epitopes of that antigen bind to B-lymphocytes and T-lymphocytes by means of epitope-specific receptor molecules having a shape complementary to that of the epitope.
• Epitopes are the portions or fragments of an antigen that react with antibodies.
• Adaptive immunity involves The production of antibody molecules, Production of cytotoxic T-lymphocytes (CTLS), Activate macrophages and NK cells, and the Production of cytokines.
• Antigen-presenting cells (APCs) such as macrophages and dendritic cells help trigger adaptive immune responses
• Adaptive immunity involves two types immune responses: 1. Humoral immunity; involves production of antibody molecules in response to an antigen and is mediated by B-lymphocytes, 2. Cell-mediated immunity: involves the production of cytotoxic T-lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen and is mediated by T-lymphocytes.

Organs and Cells of the Immune System

• The organs and cells of the immune system include a broad range of responses for microbes, along with external and internal defenses.
• These factors act against specific pathogens or changed body cells, and against foreign bodies, injuries and pathogens.
• Lymphoid System is part of the immune system.
• Collection of tissues and organs designed to bring B and T cells in contact with antigens.
• Key lymphoid organs:
• Primary lymphoid organs: Bone marrow, Thymus,
• Secondary lymphoid organs: Lymph nodes, Spleen, Peyer's patches, Appendix

Bone Marrow

• This organ is found in the center of most bones (Ribs, Vertebrae, and Pelvis) and has many blood vessels.
• There are two types of bone marrow: red and yellow.
• Red marrow contains blood stem cells that can become red blood cells, white blood cells, or platelets.
• Yellow marrow is made mostly of fat.
• Bone marrow comprises approximately 5% of total body mass in healthy adult humans.
• All cells of the immune system initially derived from the bone marrow, in a process called Hematopoiesis.
• During hematopoiesis, stem cells differentiate into either mature cells of the immune system or into precursors of cells that migrate out of the bone marrow to continue their maturation.
• Human marrow produces approximately 500 billion blood cells per day.

Thymus

• The thymus gland is in the chest between the lungs.
• The Thymus is largest and most active during the neonatal and pre-adolescent periods (28g).
• By the early teens, the thymus begins to decrease in size and activity and the tissue of the thymus is gradually replaced by fatty tissue.
• In elderly individuals the thymus weighs 5 g.
• Thymus produces and releases several hormones including Thymopoietin that Fuels the production of T-cells and Tells the pituitary gland to release Thymosin and thymulin which help make specialized types of T-cells.
• The function of the thymus is to produce mature T cells.
• Immature thymocytes (prothymocytes) leave the bone marrow and migrate into the thymus.
• Through maturation process referred to as Thymic education, T cells that are beneficial to the immune system are spared, while those T cells that might evoke an autoimmune response are eliminated.
• T cells that successfully develop react appropriately with MHC immune receptors of the body.
• Mature T cells are released into the bloodstream, while abnormalities of the thymus can result in a decreased number of T cells and autoimmune diseases.
• These are often associated with cancer of the thymus tissue, called Thymoma.

Spleen

• A small organ inside your left rib cage, just above the stomach, and also part of the lymphatic system (which is part of he immune system), responsible for making white blood cells
• The spleen acts as an immunologic Filter of the blood.
• Spleen make up B cells, T cells, macrophages, dendritic cells, natural killer cells and red blood cells.
• The types of tissue are White pulp, which produces white blood cells, and Red pulp, which is a filter.
• It captures foreign materials (antigens) from the blood that passes through the spleen. The Spleen is considered as an immunological conference center.
• In the spleen, B cells become activated and produce large amounts of antibody
• Old red blood cells are destroyed in the spleen.

Lymph Nodes

• Lymph nodes are a immunologic filter for the body fluid known as lymph.
• Lymph nodes are found throughout the body, inhabited primarily by T cells, B cells, dendritic cells and macrophages.
• In a similar fashion as the spleen, the macrophages and dendritic cells that capture antigens present these foreign materials to T and B cells, consequently initiating an immune response.

Lymphocytes

• Lymphocytes mediate adaptive immune responses.
• Only a small proportion of the body's lymphocytes are found in the blood.
• The majority are found in lymphoid tissue.
• B lymphocytes complete their development in Bone marrow.
• T lymphocytes pass from their origin in the bone marrow into the Thymus, where they complete developmen

B Lymphocytes

• B cells constitute approximately 15% of peripheral blood leukocytes and arise from hemopoietic stem cells in the bone marrow. Mediate humoral immunity antibody production and have B-cell receptors on their surface for antigen recognition. Generally, 10-20% of the lymphocyte are B-lymphocytes.
• B-cells are activated by the binding of antigen to receptors on its cell surface which causes the cell to divide and proliferate.
• Some stimulated B-cells become plasma cells,which secrete antibodies.
• Others become long-lived memory B-cells which can be stimulated at a later time to differentiate into plasma cells.

T Lymphocytes

• T-lymphocytes arise from stem cells in the bone marrow. Migrate to the thymus where they differentiate into mature T-cells. Surface proteins expressed: TCR, CD4 or CD8. Leave thymus and circulate in the bloodstream. Move to peripheral lymphoid tissues. Generally, 60-80% of the lymphocytes are T-lymphocytes.
• Mediate cellular immunity (the production of cytotoxic T-lymphocytes and cytokines).
• There are two major classes of T-lymphocytes based on the surface proteins: T-lymphocytes: (CD4T-lymphocytes) have CD4 molecules and T-cell receptors (TCRS) on their surfac, T8-lymphocytes: (CD8T-lymphocytes) have CD8 molecules and T-cell receptors (TCRS) on their surface for antigen recognition.
• In the thymus, T cells multiply and differentiate into Helper T cells Cytotoxic T cells and Memory T cells
• Once stimulated by the appropriate antigen, helper T cells secrete chemical messengers (cytokines) stimulating the differentiation of B cells into plasma cells.
• Cytotoxic T cells, which are activated by various cytokines, bind to and kill infected cells and cancer cells.

Helper T Cells

• Also called CD4 cell, T helper cell, or helper T lymphocyte.
• A type of white blood cell that serves as a key mediator of immune function.
• Helper T cells play a central role in normal immune responses by producing factors that activate virtually all other immune system cells.
• Some cells include: B cells, Cytotoxic T cells, and Macrophages and other cells, which attack invading pathogens (disease-causing agents).
• Surface proteins also provide critical role in helper T cell activation by binding MHC2 molecules, which help the immune system recognize foreign substances.
• Helper T cells can be divided into two genera subpopulations: Th1 and Th2 cells. These populations can be distinguished by the cytokines they secrete.
• T cells primarily produce the cytokines Interferon (gamma), tumour necrosis factor-beta, and interleukin-2, Th 2 cells mainly synthesize the interleukins, IL-4, IL-5, IL-6, IL-9, IL-10, and IL-13.
• The main role of the Th1 cells is to stimulate cell-mediated responses (cytotoxic T cells an macrophages), while Th2 cells primarily assist in stimulating B cells to make antibodies

Natural Killer Cells

• Natural Killer (NK) Cells are lymphocytes in the same family as T and B cells, coming from a common progenitor.
• As cells of the innate immune system, NK cells are classified as group I Innate Lymphocytes (ILCs) and respond quickly to a wide variety of pathological challenges
• They are considered part of innate immunity while B and T cells participate in adaptive immunity.
• Human NK cells normally constitute 5-15% of peripheral blood (PB) lymphocytes.
• Also present in relative abundance in the bone marrow, liver, uterus, spleen, and lung, and in secondary lymphoid tissues, as well as some mucosal associated lymphoid tissues (MALT).
• Kill cells bound by antibody.

Macrophages

• Sentinal (guard) cells that can be found below the surface in all areas of the body which are exposed to the outside that are prime targets for microbial infection.
• When monocytes leave the blood and enter the tissue, they become activated and differentiate into macrophages.
• Macrophages are important in the regulation of immune responses.
• In tissues, they are relaxed, functioning primarily as garbage collectors in a resting state
• Dying cells give of “find me” signals so they can be destroyed.
• Best signal of activation is an intercellular communication molecule, interfon gamma" y

Hyperactivation

• Macrophages grow larger and increase their of phagocytosis.
• They can ingest invaders as big as unicellular parasites.
• They also produce and secrete a cytokine, tumor necrosis function
• Secrete proteins called cytokines

Dendritic Cells

• Originate in the bone marrow and function as anitgen presenting cells (APC), also are the more effecient APCs than macrophages
• Their main function is to process antigen material and surface the T cells of the immune system
• Act as a messangers between innate and adaptive immune systems, as well as the lymphoid organs, as well as circulation
• Called Langerhans cells when located in epidermis (also poorly phagocytic)
• Immature dendritic cells are in skin and and mucous membranes that engulf microbes and morecules tru phagocytosis
• They also create cytokines such as tumor necrosis factor.

Neutrophils

• Part of the immune system and numbers in blood total 20 billion cells
• Account for 70% of white blood cells and only last five days
• Are not antigen cells but instead “prosffesional kills” and make cytokines

Explore innate characteristics and their definitions. Differentiate between innate and adaptive traits. Understand how these characteristics relate to an organism's development.