Lymphocyte

lymphocyteslymphocyticlymphoidlymphoid cellslymphocyte countimmune cellslymphocyte subsetslymphocytic infiltrationtotal lymphocyte countB-lymphoid cells
A lymphocyte is one of the subtypes of white blood cell in a vertebrate's immune system.wikipedia
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Natural killer cell

natural killer cellsNK cellsnatural killer
Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity).
Natural killer cells, or NK cells, are a type of cytotoxic lymphocyte critical to the innate immune system.

White blood cell

leukocyteleukocyteswhite blood cells
A lymphocyte is one of the subtypes of white blood cell in a vertebrate's immune system.
These broadest categories can be further divided into the five main types: neutrophils, eosinophils (acidophiles), basophils, lymphocytes, and monocytes.

T cell

TT lymphocytesT-cells
Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity).
A T cell, or T lymphocyte, is a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity.

B cell

BB lymphocytesB-cell
Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity).
B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype.

Adaptive immune system

adaptive immunityadaptive immune responseadaptive
Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity).
This mechanism allows a small number of genes to generate a vast number of different antigen receptors, which are then uniquely expressed on each individual lymphocyte.

Bone marrow

marrowred bone marrowbone marrow stroma
T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response.
All types of hematopoietic cells, including both myeloid and lymphoid lineages, are created in bone marrow; however, lymphoid cells must migrate to other lymphoid organs (e.g. thymus) in order to complete maturation.

Lymph

lymphaticlymphatic fluidlymph fluid
They are the main type of cell found in lymph, which prompted the name "lymphocyte".
It is then transported through larger lymphatic vessels to lymph nodes, where it is cleaned by lymphocytes, before emptying ultimately into the right or the left subclavian vein, where it mixes back with the blood.

Immunity (medical)

immunityimmuneimmune response
Throughout the lifetime of an animal, these memory cells will "remember" each specific pathogen encountered, and are able to mount a strong and rapid response if the same pathogen is detected again; this is known as acquired immunity.
The adaptive system is composed of more advanced lymphatic cells that are programmed to recognise self-substances and don't react.

Lymphopoiesis

common lymphoid progenitormultipotent progenitorlymphocytopoiesis
The formation of lymphocytes is known as lymphopoiesis.
Lymphopoiesis (lĭm'fō-poi-ē'sĭs) (or lymphocytopoiesis) is the generation of lymphocytes, one of the five types of white blood cell (WBC).

Immune system

immuneimmune responseimmune responses
A lymphocyte is one of the subtypes of white blood cell in a vertebrate's immune system.
However, a distinct lymphocyte-derived molecule has been discovered in primitive jawless vertebrates, such as the lamprey and hagfish.

Lymphatic system

lymphoidlymphoid tissuelymphatic
Following maturation, the lymphocytes enter the circulation and peripheral lymphoid organs (e.g. the spleen and lymph nodes) where they survey for invading pathogens and/or tumor cells.
Lymph is very similar to blood plasma: it contains lymphocytes.

Haematopoiesis

hematopoietichematopoiesishaematopoietic
This process is called haematopoiesis.
Lymphocytes are the cornerstone of the adaptive immune system. They are derived from common lymphoid progenitors. The lymphoid lineage is composed of T-cells, B-cells and natural killer cells. This is lymphopoiesis.

Major histocompatibility complex

MHCmajor histocompatibility complex (MHC)HLA loci
NK cells distinguish infected cells and tumors from normal and uninfected cells by recognizing changes of a surface molecule called MHC (major histocompatibility complex) class I.
As a lineage of leukocytes, lymphocytes reside in peripheral lymphoid tissues, including lymphoid follicles and lymph nodes, and include B cells, T cells, and natural killer cells (NK cells).

Cytokine

cytokineschemical signalsinflammatory chemical signals
In response to pathogens some T cells, called T helper cells, produce cytokines that direct the immune response, while other T cells, called cytotoxic T cells, produce toxic granules that contain powerful enzymes which induce the death of pathogen-infected cells.
The activity of interferon-gamma (the sole member of the interferon type II class) was described in 1965; this was the first identified lymphocyte-derived mediator.

Thymus

thymus glandthymicmedulla
T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response.
Defects that affect both the T cell and B cell lymphocyte lineages result in severe combined immunodeficiency (SCID).

Bursa of Fabricius

bursaBursa of Fabricuisbursae of Fabricius
T cells (thymus cells) and B cells (bone marrow- or bursa-derived cells) are the major cellular components of the adaptive immune response.
These plicae have hundreds of bursal follicles containing follicle-associated epithelial cells, lymphocytes, macrophages, and plasma cells.

Lymph node

lymph glandslymph glandfollicle
In the circulatory system, they move from lymph node to lymph node.
Lymph nodes are major sites of B and T lymphocytes, and other white blood cells.

Macrophage

macrophagesTissue macrophagesCD68 + macrophages
This contrasts with macrophages, which are rather stationary in the nodes.
Besides phagocytosis, they play a critical role in nonspecific defense (innate immunity) and also help initiate specific defense mechanisms (adaptive immunity) by recruiting other immune cells such as lymphocytes.

Spleen

splenicsplenetichilum
Following maturation, the lymphocytes enter the circulation and peripheral lymphoid organs (e.g. the spleen and lymph nodes) where they survey for invading pathogens and/or tumor cells.
Storage of red blood cells, lymphocytes and other formed elements. The spleen of horses stores roughly 30% of the red blood cells and can release them when needed. In humans, up to a cup (240 ml) of red blood cells is held in the spleen and released in cases of hypovolemia and hypoxia. It can store platelets in case of an emergency and also clears old platelets from the circulation. Up to a quarter of lymphocytes are stored in the spleen at any one time.

Lymphocytosis

atypical lymphocytosishigh lymphocyte countsincreased blood lymphocytes
A general increase in the number of lymphocytes is known as lymphocytosis, whereas a decrease is known as lymphocytopenia.
Lymphocytosis is an increase in the number of lymphocytes in the blood.

Lymphocytopenia

lymphopeniaB lymphopeniadecreased lymphocyte count
A general increase in the number of lymphocytes is known as lymphocytosis, whereas a decrease is known as lymphocytopenia.
Lymphocytopenia, or lymphopenia, is the condition of having an abnormally low level of lymphocytes in the blood.

Cytotoxicity

cytotoxiccytotoxincytotoxins
Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adaptive immunity), and B cells (for humoral, antibody-driven adaptive immunity).
Antibody-dependent cell-mediated cytotoxicity (ADCC) describes the cell-killing ability of certain lymphocytes, which requires the target cell being marked by an antibody.

Lymphoma

lymphomaslymphatic cancerlymphosarcoma
A high lymphocyte count with a low neutrophil count might be caused by lymphoma.
Lymphoma is a group of blood cancers that develop from lymphocytes (a type of white blood cell).

Blood film

blood smearperipheral blood smearblood smears
Microscopically, in a Wright's stained peripheral blood smear, a normal lymphocyte has a large, dark-staining nucleus with little to no eosinophilic cytoplasm.
Lymphocytes have very little cytoplasm and a large nucleus (high NC ratio) and are responsible for antigen-specific immune functions, either by antibodies (B cell) or by direct cytotoxicity (T cell). The distinction between B and T cells cannot be made by light microscopy.

Leukemia

leukaemialeukemiasleukemic
An increase in lymphocyte concentration is usually a sign of a viral infection (in some rare case, leukemias are found through an abnormally raised lymphocyte count in an otherwise normal person).
In lymphoblastic or lymphocytic leukemias, the cancerous change takes place in a type of marrow cell that normally goes on to form lymphocytes, which are infection-fighting immune system cells. Most lymphocytic leukemias involve a specific subtype of lymphocyte, the B cell.