Immune System - Cells and Organs

Flashcards about the Immune System Cells and Organs, covering topics from a lecture by G.Shengelidze.

Epigenetic Changes in Innate Immunity

The ability of innate immune system cells to be trained by past infections or exposures, resulting in an enhanced response to triggers; involves epigenetic reprogramming of transcriptional pathways.

Phagocytes

Cells of the innate immune system that ingest and destroy microbes and remove damaged tissues; examples include neutrophils, monocytes, macrophages, and eosinophils.

Phagocytosis

A process where cells ingest and destroy microbes.

Dendritic Cells

Cells that express pattern recognition receptors (PRRs) and act as principal antigen-presenting cells linking innate and adaptive immunity.

Neutrophils

Rapid, short-lived phagocytes with enzymatic activity, originating from HSCs in bone marrow; major response is degranulation; low levels of cytokine production.

Monocytes/Macrophages

Phagocytes that circulate in the blood and become macrophages in tissues; provide prolonged defense, produce cytokines that regulate inflammation, and clear dead tissue.

Chemotactic Factors

Attractants that neutrophils are drawn to:

NET Formation

A process where neutrophils extrude nuclear contents to immobilize and kill extracellular microbes, potentially damaging healthy tissues.

Mononuclear Phagocyte System

A system including circulating monocytes and tissue-resident macrophages derived from yolk sac or hematopoietic precursors.

M1 Macrophages

Macrophages polarized by IFN-γ, TNF-α, or LPS, involved in pro-inflammatory responses, infection protection, and anti-cancer immunity.

M2 Macrophages

Macrophages polarized by IL-4, IL-10, or IL-13, involved in anti-inflammatory responses, tissue repair, angiogenesis, and immunosuppression.

Mast Cells

White blood cells that release granules filled with chemicals, such as histamine, to cause inflammation; reside in tissues.

Basophils

White blood cells with granules released by inflammatory, infectious, and allergic triggers; contribute to inflammation in severe allergies (anaphylaxis); located in the blood.

Eosinophils

White blood cells containing granules that kill cells marked for destruction, clear parasitic infections, and mediate inflammation; circulate in blood and migrate to tissues interacting with the environment.

Antibody-Dependent Cellular Cytotoxicity (ADCC)

A method of killing where immune cell recognizes specific antibody bound to a cell and causes it to die without complement.

Dendritic Cells (DCs)

Tissue-resident and circulating cells that detect microbes, initiate innate immune defense reactions, and capture microbial proteins for T cell display.

Classical DCs (cDCs)

DCs involved in capturing protein antigens and presenting them to T cells.

Plasmacytoid DCs (pDCs)

DCs that produce antiviral cytokine type I interferon (IFN) in response to viruses.

Monocyte-Derived DCs (MoDCs)

DCs derived from monocytes recruited into tissue inflammatory sites, with functions similar to cDCs.

Langerhans Cells

DCs found in the epidermis, sharing functions with cDCs but related to tissue-resident macrophages.

Follicular Dendritic Cells (FDCs)

A population of cells involved in B cell activation in the germinal centers of secondary lymphoid organs.

Natural Killer (NK) Cells

Lymphoid cells that do not express antigen-specific receptors but can alter behavior based on prior antigen exposure, controlling infections and tumors.

NK cell receptors

Unique innate immune cell type that recognize and respond to the respective ТLR ligands directly; central to killer cell, activating receptors are central to the killer function.

Innate Lymphoid Cells (ILCs)

Lymphoid cells found in tissues (skin, lungs, gastrointestinal tract) that react to signals from infected/injured tissues by releasing cytokines; some have cytolytic potential.

Primary Lymphoid Organs

Sites of lymphocyte formation, including bone marrow and thymus.

Secondary Lymphoid Organs

Sites where B and T cells proliferate, including lymph nodes, spleen, Peyer’s patches, and tonsils.

Lymph

Fluid that drains from tissues into the lymphatic system and eventually into subclavian veins.

Lymph Nodes

Sites where lymph fluid drains and dendritic cells present processed antigens to T cells, leading to adaptive immune responses.

Lymphoid Follicles

Site of B-cell activation; contain follicular dendritic cells.

Paracortex

Contains T cells activated by dendritic cells and antigen; contain high endothelial venules

Medulla

Contain macrophages that filter lymph and plasma cells secreting antibodies.

Spleen

Organ that filters blood (no lymph) and contains white pulp and red pulp.

White pulp of Spleen

Exposure to B and T cells Exposure to macrophages

Red pulp of Spleen

Filters blood in sinusoids Removes old RBCs (red) Stores many platelets

White pulp

Organ where marginal zone macrophages remove debris and dendritic cells process antigen; contains B cells in follicles and T cells in periarteriolar lymphocyte sheath (PALS).

Sinusoids of the Spleen

Composed of vascular sinusoids and splenic cords with macrophages for filtration.

Strep pneumo

Predominant pathogen for sepsis

Howell-Jolly Body

Nuclear remnants