Immunity refers to the body's ability to resist infections and diseases. All cells and tissues that provide immunity collectively form the immune ...

The lymphatic system provides structural and functional support to the immune system against pathogens. The lymphoid organs, lymph, and lymphatic vessels ...

Lymphatic vessels, or lymphatics, transport lymph from peripheral tissues to the venous system. The journey of lymph begins in the thin-walled lymphatic ...

Lymphoid cells and lymphoid tissues are the two major components of lymphoid organs. Lymphoid cells consist of immune system cells such as B and T ...

The thymus and red bone marrow are the two primary lymphoid organs that are sites for lymphocyte production and maturation. Red bone marrow is primarily ...

Secondary lymphoid organs, such as the spleen, lymph nodes, and mucosa-associated lymphoid tissues or MALT, are the sites where lymphocytes first ...

Lymph nodes are bean-shaped structures that cluster along the lymphatic vessels in the inguinal, axillary, and cervical regions. Each node is divided into ...

The mesoderm cells of the developing veins form the precursor lymphatic vessels and nodes called lymph sacs. The paired jugular lymph sacs are the first ...

Present from birth, innate immunity is the body's first line of defense against a wide range of harmful pathogens. It provides immediate, non-specific ...

Surface barriers such as the skin and mucous membranes are the body's initial defense against pathogens, offering physical and chemical protection. ...

The two essential cells involved in the innate immune responses are phagocytes and natural killer, or NK cells. Phagocytes — microphages and ...

Antimicrobial proteins, such as interferons, the complement system, iron-binding proteins, and antimicrobial peptides, enhance the immune response by ...

The complement system consists of about 20 plasma proteins, working together to fortify the body's defense against infections through opsonization, ...

Immune surveillance involves monitoring peripheral tissues to detect pathogens and infected or cancerous body cells. Natural killer, or NK cells, which ...

An inflammatory response is a localized, non-specific immune reaction marked by redness, swelling, heat, pain, and occasional loss of function. Any ...

The adaptive immune system provides a specialized defense using T and B lymphocytes with specific features to combat infections effectively. These cells ...

In the bone marrow, the common lymphoid progenitor cells give rise to precursors for T and B lymphocytes. Next, these precursors mature to gain ...

Complete antigens, or simply antigens, are large, complex foreign molecules, mainly proteins, that initiate an immune response. They possess two key ...

Antigen receptors are multiprotein complexes on the B and T cell membranes that recognize specific antigens. A B cell antigen receptor, or BCR, is a ...

Antigen-presenting cells, also known as APCs, process foreign antigens, such as fragments from pathogens, for recognition by T cells. When an APC engulfs ...

The antigen-processing pathways break down antigens for presentation to lymphocytes. The endogenous and exogenous pathways are the two main ...

Naive T cells express membrane proteins called the cluster of differentiation, or CD markers with the T cell receptor or TCR. There are two major T cell ...

Activated T cells with CD4 markers give rise to the effector helper and regulatory T cells, while the effector cytotoxic T cells arise from T cells with ...

Cytotoxic T cells target body cells infected by viruses, intracellular bacteria, or parasites. They also eliminate cancerous cells and foreign cells ...

Naive B cells become sensitized when they encounter their corresponding antigen, which binds to the B cell receptor, or BCR, on the cell surface. After ...

Antibodies, also known as immunoglobulins, are soluble proteins produced by effector B cells called plasma cells in response to foreign substances like ...

Antibodies recognize and bind antigens to form antigen-antibody complexes for pathogen elimination. After binding to an antigen, the antibody neutralizes ...

Immunological memory is the ability to react faster to the antigens that have previously activated the immune response. This occurs due to long-lived ...

Active immunity refers to the process by which an individual's immune system is stimulated to produce a protective response to a pathogen, typically ...

Cell-mediated immunity in a fetus begins at the third month of growth, and active antibody-mediated immunity follows about one month later. The first ...

The immune defense against pathogenic bacteria involves phagocytes like macrophages from the innate system along with the T and B cells from the adaptive ...

Upon viral infection, cells secrete interferons to protect uninfected cells and activate the patrolling NK cells to initiate a non-specific innate immune ...

Immunodeficiency diseases occur due to exposure to immunosuppressive agents, poor development of lymphoid organs, or viral infections. Prolonged use of ...

Hypersensitivity, or allergic reaction, occurs when the immune system overreacts to an allergen. Hypersensitivity can be of four types. Type I or ...

In an autoimmune disorder, the body's immune system mistakenly attacks its own cells and tissues by activating self-reactive T and B cells. There are ...

Tissue transplantation is a complex yet vital medical procedure that involves transferring cells, tissues, or organs from a donor to a recipient to ...

Cancer immunotherapy aids the body's immune system to identify and eliminate cancer cells, using vaccines, oncolytic viruses, activated patient T ...

Cancer vaccination can be preventive, protecting against oncogenic agents, or active, combating existing cancerous cells. Like traditional vaccines, ...