II. Characteristics

  1. Forms in Bone Marrow from Lymphoblasts (which are in turn derived from stem cells)
  2. Function: Primary source of viral defense and Antibody
    1. Adaptive Immunity (learned response)
      1. B-Lymphocytes
        1. Humoral Immunity with Antibody against extracellular antigens
      2. T-Lymphocytes
        1. Cellular Immunity via T-Helper/CD4+ Cells and T-Cytotoxic/CD8+ Cells
    2. Innate Immunity
      1. Natural Killer Cells (NK cells)
        1. Lymphocytes providing immediate protection against Intracellular Bacteria, viruses, cancer cells
  3. Morphology on Blood Smear
    1. Mononuclear Leukocytes (same class as Monocytes)
    2. Small cells with minimal cytoplasm

III. Types: B-Lymphocytes (B Cells)

  1. B-Cells are responsible for Humoral Immunity
    1. B-Cells are named for where they were first found (Bursa of Fabricus in birds)
    2. Responsible for antigen-specific Antibody (plasma cells) and secondary future responses (memory cells)
  2. Derivation
    1. Fetal Liver
    2. Bone Marrow Pluripotent Stem Cells
  3. Peripheral Migration to Secondary Lymphoid Tissue
    1. Spleen
    2. Lymph Nodes
    3. Peyer's Patches (Small Bowel)
  4. Activation
    1. Recognition
      1. Antigen binds B-Lymphocyte Surface Receptor (BCR)
      2. BCR binding activates B-Lymphocyte
        1. T-Cell Independent Antigen (e.g. inert antigens) alone activate B-Cells
        2. T-Cell Dependent Antigen (e.g. microbes) require added stmulus (e.g. T Cells)
    2. B-Cell Proliferation
      1. Activated Lymphocytes proliferate
    3. B-Cell Differentiation
      1. Plasma Cells (Antibody producing cells)
        1. Survive for days to weeks producing antibodies, and without replicating
      2. Memory Cells
        1. Remain in B-Lymphocyte pool ready to respond to the same antigen in future
        2. Future antigen response is known as secondary immune response

IV. Types: T-Lymphocytes (T-Cells)

  1. T-Cells are responsible Cell-Mediated Immunity
    1. T-Cells target Intracellular Pathogens (e.g. viruses and Intracellular Bacteria) and cancer cells
  2. T-Cells
    1. Derived in Bone Marrow
    2. Migrate to Thymus
      1. Maturation and Differentiation into two cell lines with different T-Cell Receptors (CD4 and CD8)
    3. Release into peripheral circulation
  3. T-Cell Surface Receptors
    1. T-Cell Receptors (TCR)
      1. Bind the antigen on the antigen presenting cell
      2. TCR Types
        1. TCR-alpha-beta (TCRab+)
        2. TCR gamma-delta (TCRgd+)
    2. T-Cell Co-Receptors
      1. CD4 binds peptide/antigen-MHC class 2 complex on surface of antigen presenting cells
      2. CD8 binds peptide/antigen-MHC class 1 complex on surface of antigen presenting cells
  4. T-Cell Types
    1. Effector Cells
      1. T-Helper Cells (CD4+ Cells)
        1. Releases interferon
          1. Stimulates Phagocytosis by Macrophages
          2. Activates Natural Killer Cells
          3. Suppresses viral replication
        2. Releases interleuken 2
          1. Promotes T-Cell proliferation (esp. memory cells)
          2. Promotes B-Cell proliferation (memory cells and plasma cells)
      2. T-Cytotoxic Cells (CD8+ Cells)
        1. Target and destroy tumor cells and virus-infected cells
    2. Other Cells
      1. Memory Cells
      2. Apoptosis of some cells not otherwise differentiated
  5. Naive T-Cell Activation
    1. T-Cell Receptor (TCR) binds to MHC-Antigen complex on Antigen Presenting Cells
    2. T-Cell Surface CD28 binds to B7 Ligand on antigen presenting cell
    3. T-Cell Surface LFA-1 (Lymphocyte Function Associated Antigen) binds ICAM1 on antigen presenting cells
    4. Interleukin-2 (IL2) produced by naive T Cells
      1. Stimulate T Cell proliferation

V. Types: Natural Killer Cells (NK cells)

  1. Lymphocytes providing protection against Intracellular Bacteria and viruses, as well as cancer cells
  2. Part of Innate Immunity in which response is not based on prior exposure to pathogen
    1. Contrast with B-Cells and T-Cells which have a learned pathogen response (Adaptive Immunity)
  3. NK cells bind Major Histocompatibility Complex 1 (MHC-1)
    1. MHC-1 is present on normal cells and it inactivates NK cells
    2. MHC-1 is NOT expressed by infected cells
      1. NK activating receptor Ligand is expressed
      2. NK cells bind infected cells and destroy them
  4. NK cell mechanisms of infected cell destruction
    1. Cytoplasmic granules
      1. Perforin
        1. Generates pores on cells targeted for destruction
      2. Granzyme
        1. Induces programmed cell death (apoptosis) on entry into Target Cells
    2. Cytokines
      1. Interferon-Gamma (IFN-g)
        1. Activates Macrophages for Phagocytosis

VI. Labs: Normal

  1. Percentage Lymphocytes: 15-40% of White Blood Cells
  2. Total Lymphocytes: 800-2600/mm3
  3. Total T Lymphocytes: 800-2200/mm3
    1. T helper Cells: >400/mm3
    2. T suppressor Cells: 250-750/mm3
    3. Helper Cell to Suppressor Cell ratio: >0.9
    4. CD2 Percentage of Lymphocytes: 65-85%
    5. CD4 Percentage of Lymphocytes: 45-75%

VII. Causes: Increased (Lymphocytosis)

  1. Increased Absolute Lymphocyte Count (>4500/mm3)
    1. Non-activated Lymphocytes
      1. Influenza
      2. Pertussis
      3. Tuberculosis
      4. Mumps
      5. Varicella
      6. Herpes Simplex Virus
      7. Rubeola
      8. Brucellosis
      9. Fungal infection
      10. Rickettsial infection
      11. Chronic Lymphocytic Leukemia
      12. Acute Lymphoblastic Leukemia
    2. Activated Lymphocytes (Atypical lymphocytes)
      1. Cytomegalovirus Infection
      2. Infectious Mononucleosis
      3. Infectious Viral Hepatitis
      4. Toxoplasmosis
      5. Syphilis
      6. Post-transfusion
      7. Beta Streptococcus
      8. Medication
        1. Mephenytoin
        2. Dilantin
        3. Para-aminosalicylic acid
  2. Increased Relative Lymphocyte Count (>40% of total)
    1. Normal finding in children under age 2 years
    2. Acute stage of viral infection
    3. Connective Tissue Disease
    4. Hyperthyroidism
    5. Addison's Disease
    6. Splenomegaly

VIII. Causes: Decreased

  1. AIDS
  2. Bone Marrow suppression
  3. Aplastic Anemia
  4. Neoplasms
  5. Steroids
  6. Adrenocortical hyperfunction
  7. Neurologic Disorders
    1. Multiple Sclerosis
    2. Myasthenia Gravis
    3. Gullain Barre Syndrome

IX. Evaluation: Lymphocytosis (Lymphocytes >4500/mm3)

  1. See Leukocytosis
  2. History and potential causes
    1. Contagious contacts
    2. Immunization history
  3. Diagnostics (consider)
    1. Viral specific studies (e.g. Monospot)
    2. Chest XRay

Images: Related links to external sites (from Bing)

Related Studies

Ontology: B-Lymphocytes (C0004561)

Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (CHV) White blood cells that make antibodies and are an important part of the immune system
Definition (NCI) Immunologically important lymphocyte that is not thymus-dependent, is either short-lived and naive or long-lived and of memory phenotype, and resembles the bursa-derived lymphocyte of birds in that it is responsible for the production of immunoglobulins.
Definition (NCI_NCI-GLOSS) A type of immune cell that makes proteins called antibodies, which bind to microorganisms and other foreign substances, and help fight infections. A B lymphocyte is a type of white blood cell.
Definition (MSH) Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.
Definition (CSP) lymphoid cells concerned with humoral immunity; they are short lived cells resembling bursa derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation.
Concepts Cell (T025)
MSH D001402
SnomedCT 112130006
LNC LP15088-5, LP36861-0, MTHU002435, LA4275-9
English B-Cell, B-Cells, Bursa Dependent Lymphocytes, Bursa-Dependent Lymphocyte, Bursa-Dependent Lymphocytes, Lymphocyte, Bursa-Dependent, Lymphocytes, Bursa-Dependent, LYMPHOCYTES B, lymphocyte B cells, bursa-equivalent lymphocyte, lymphocyte B cells (lab test), B-lymphocyte, b-lymphocyte, b-lymphocytes, b cell, b lymphocyte, b cells, b-cell, b lymphocytes, b-cells, Lymphocytes B, B cells, B Cell Lymphocyte, B lymphocyte, B cell, B-cell, B lymphocyte (cell), B-Lymphocytes, B Cells, B Lymphocytes, B-Lymphocyte, B Cell
French Lymphocyte B, Cellules B, Lymphocytes B, Lymphocytes bursodépendants, Lymphocytes burso-dépendants, Ly B
Swedish B-lymfocyter
Czech B-lymfocyty
Finnish B-imusolut
Italian Cellule B, Linfociti bursa-dipendenti, Linfociti B
Japanese B細胞, Bリンパ球, Bリンパ細胞, ファブリキウス嚢依存性リンパ球, リンパ球-B, リンパ球-ファブリキウス嚢依存性, 嚢依存リンパ球
German LYMPHOZYTEN B, B-Lymphozyten, B-Zellen, Bursa-abhängige Lymphozyten
Latvian B-šūnas, B-limfocīti
Polish Limfocyty B
Norwegian B-celler, Bursa-avhengige lymfocytter, B-lymfocytter
Spanish célula B, linfocito B (célula), linfocito B, Linfocitos B, Linfocitos Bursa-Dependientes, Células B
Dutch B-cellen, B-lymfocyt, B-lymfocyten, Bursa-afhankelijke lymfocyten, Lymfocyt, B-
Portuguese Células B, Linfócitos B, Linfócitos Bursa-Dependentes

Ontology: Natural Killer Cells (C0022688)

Definition (MSH) Bone marrow-derived lymphocytes that possess cytotoxic properties, classically directed against transformed and virus-infected cells. Unlike T CELLS; and B CELLS; NK CELLS are not antigen specific. The cytotoxicity of natural killer cells is determined by the collective signaling of an array of inhibitory and stimulatory CELL SURFACE RECEPTORS. A subset of T-LYMPHOCYTES referred to as NATURAL KILLER T CELLS shares some of the properties of this cell type.
Definition (MSHCZE) Lymfocyty získané z kostní dřeně, které mají cytotoxické vlastnosti, přirozeně namířené proti transformovaným buňkám a buňkám infikovaným virem. NK buňky nejsou na rozdíl od T buněk a B buněk antigenově specifické (projevuje se nespecifickou imunitou). Cytotoxicita těchto buněk je zajištěna pomocí receptorů na povrchu buněk, které společně signalizují stavy inhibice a stimulace buněk. Jedná se o podskupina T-LYMPHOCYTŮ, která bývá označována jako „přirození zabíječi“ (NKT BUŇKY) (angl. natural killers) a sdílí s těmito buňkami některé vlastnosti. R
Definition (NCI) Natural killer cells are cells that resemble large granular lymphocytes. They do not express markers of either T or B cell lineage. They are positive for CD16, CD56, and CD 94. These cells do possess Fc receptors for IgG and can kill target cells using antibody-dependent cell-mediated cytotoxicity. They can also use perforin to kill cells in the absence of antibody and killing may occur without previous sensitization.
Definition (NCI_NCI-GLOSS) A type of immune cell that has granules (small particles) with enzymes that can kill tumor cells or cells infected with a virus. A natural killer cell is a type of white blood cell.
Definition (PSY) White blood cells that kill tumor- and virus-infected cells as part of the body's immune system.
Definition (CSP) type of cytotoxic leukocytes which attack and kill virus-infected or neoplastic cells independent of antibody coating or MHC restriction; may be derived from lymphocytes or monocytes.
Concepts Cell (T025)
MSH D007694
SnomedCT 259717003
LNC LA4573-7
English Cell, Natural Killer, Cell, NK, Cells, Natural Killer, Cells, NK, Killer Cell, Natural, Killer Cells, Natural, NK Cells, K lymphocyte, Killer cell, K cell, NK-cell (cell), Natural killer (NK)-cell, Natural killer cell, NK cell, nk cell, nk-cell, natural killer cells, nk cells, cells natural killer, Natural killer cell (cell), Natural killer (NK)-cell (cell), natural killer cell, NK-LGL, killer cell, NK (natural killer) cell, NK-cell, NK-cell (body structure), Natural Killer Cell, NK Cell, Killer Cell, NK-Cell, NK, Natural Killer Cells
Spanish célula NK, linfocito K, Células Asesinas Naturales, Células Killer Naturales, célula natural killer, célula asesina natural, Células Killer, linfocito citolítico natural (célula), linfocito citolítico natural, Células NK
French Cellule tueuse naturelle, Cellules tueuses naturelles, Cellules NK, Cellule NK
Swedish Mördarceller, naturliga
Czech buňky NK, buňky natural killer
Finnish Luonnolliset tappajasolut
Italian Cellule NK, Cellule Natural Killer
Japanese NK細胞, キラー細胞-ナチュラル, ナチュラルキラー細胞
Polish Komórki NK, Komórki natural killer, Komórka-naturalny zabójca, Komórki naturalnej cytotoksyczności
Norwegian Natural killer-celler, Drepeceller, naturlige, Naturlige drapsceller, Drapsceller, naturlige, Naturlige drepeceller, NK-celler
Portuguese Células Exterminadoras, Células Destruidoras, Células Killer, Células Natural Killer, Células Destruidoras Naturais, Células Assassinas, Células Killer Naturais, Células Assassinas Naturais, Células Exterminadoras Naturais, Células NK, Células Matadoras Naturais
German NK-Zellen, Killerzellen, natürliche, Natürliche Killerzellen
Dutch K-cel, Killercellen, Natural-killercel, Natural-killercellen

Ontology: Lymphocyte (C0024264)

Definition (MSH) White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS.
Definition (NCI_NCI-GLOSS) A type of immune cell that is made in the bone marrow and is found in the blood and in lymph tissue. The two main types of lymphocytes are B lymphocytes and T lymphocytes. B lymphocytes make antibodies, and T lymphocytes help kill tumor cells and help control immune responses. A lymphocyte is a type of white blood cell.
Definition (NCI) White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each); those with characteristics of neither major class are called null cells.
Definition (CSP) white blood cells formed in the body's lymphoid tissue.
Concepts Cell (T025)
MSH D008214
SnomedCT 56972008
LNC LP14540-6, LP30914-3, MTHU004645
English Lymphocytes, lymphocytes, lymph cell, lymphocyte, Lymphocyte (cell), Lymphocytic cell, Lymphocyte, NOS, Lymphocytic cell, NOS, Lymphocyte
Dutch lymfocyten, Lymfocyt, Lymfocyten
French Lymphocyte, Lymphocytes, Cellules lymphocytaires
Japanese リンパ球, リンパキュウ
Swedish Lymfocyter
Czech lymfocyty, Lymfocyty
Finnish Imusolut
Latvian Not Translated[Lymphocytes]
Polish Limfocyty
Hungarian Limfociták
Norwegian Lymfocytter
Spanish célula linfática, linfocito (célula), linfocito, Linfocitos
German Lymphozyten
Italian Linfociti
Portuguese Linfócitos

Ontology: Lymphocytosis (C0024282)

Definition (MSH) Excess of normal lymphocytes in the blood or in any effusion.
Definition (CSP) excess of normal lymphocytes in the blood or in any effusion.
Concepts Disease or Syndrome (T047)
MSH D008218
SnomedCT 267568006, 154832004, 67023009
English Lymphocytoses, LYMPHOCYTOSIS, lymphocytosis (diagnosis), lymphocytosis, Lymphocytosis [Disease/Finding], Lymphocytosis, Disorder characterized by lymphocytosis, Lymphocytosis (disorder), Lymphocytosis, NOS
French LYMPHOCYTOSE, Lymphocytose, Hyperlymphocytose
Portuguese LINFOCITOSE, Linfocitose
Spanish LINFOCITOSIS, linfocitosis (trastorno), linfocitosis, Linfocitosis
German LYMPHOZYTOSE, Lymphozytose
Japanese リンパ球増加症, リンパキュウゾウカショウ
Swedish Lymfocytos
Czech lymfocytóza, Lymfocytóza
Finnish Lymfosytoosi
Polish Limfocytoza
Hungarian lymphocytosis
Norwegian Lymfocytose
Dutch lymfocytose, Lymfocytose
Italian Linfocitosi

Ontology: T-Lymphocyte (C0039194)

Definition (NCI_NCI-GLOSS) A type of immune cell that can attack foreign cells, cancer cells, and cells infected with a virus. T lymphocytes can also help control immune responses. A T lymphocyte is a type of white blood cell.
Definition (NCI) A thymocyte-derived lymphocyte of immunological importance that is long-lived (months to years) and is responsible for cell-mediated immunity. T lymphocyte cells form rosettes with sheep erythrocytes and, in the presence of transforming agents (mitogens), differentiate and divide. These cells have the characteristic T3 surface marker and may be further divided into subsets according to function, such as helper, cytotoxic, etc.
Definition (CSP) lymphocytes responsible for cell-mediated immunity, formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes; when exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
Definition (MSH) Lymphocytes responsible for cell-mediated immunity. Two types have been identified - cytotoxic (T-LYMPHOCYTES, CYTOTOXIC) and helper T-lymphocytes (T-LYMPHOCYTES, HELPER-INDUCER). They are formed when lymphocytes circulate through the THYMUS GLAND and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen.
Concepts Cell (T025)
MSH D013601
SnomedCT 57184004
CPT 1011953
LNC LP14634-7, LA4470-6
English Lymphocyte, Thymus-Dependent, Lymphocytes, Thymus-Dependent, T Lymphocytes, T-Cells, T-Lymphocytes, Thymus Dependent Lymphocytes, Thymus-Dependent Lymphocyte, Thymus-Dependent Lymphocytes, LYMPHOCYTES J, lymphocytes T cells, thymus-dependent lymphocyte, lymphocytes T cells (lab test), T cells, T-lymphocyte, thymus derived lymphocyte, t-cells, t cell, t lymphocyte, t cells, t lymphocytes, t-lymphocytes, t-lymphocyte, t-cell, T Cell Lymphocyte, T lymphocyte, T cell, T-cell, T lymphocyte (cell), T Cells, T-Cell, T Cell, T-Lymphocyte
French Ly T, Lymphocytes T, Lymphocytes thymodépendants, Lymphocytes thymo-dépendants, Cellules T, Lymphocyte T
Swedish T-lymfocyter
Czech T-buňky, T-lymfocyty, T-buňka
Finnish T-imusolut
Italian Cellule T, Linfociti timo-dipendenti, Linfociti T
Japanese 胸腺依存リンパ球, 胸腺リンパ球, リンパ球-胸腺, リンパ球-T, T細胞, Tリンパ球
German LYMPHOZYTEN J, T-Lymphozyten, T-Zellen, Thymusabhängige Lymphozyten
Polish Limfocyty T
Norwegian T-celler, Thymusavhengige lymfocytter, T-lymfocytter
Spanish célula T, linfocito T (célula), linfocito T, Linfocitos Timo-Dependientes, Linfocitos T, Células T
Dutch Lymfocyt, T-, T-cel, T-lymfocyt, T-lymfocyten, Thymusafhankelijke lymfocyt
Portuguese Células T, Linfócitos Timo-Dependentes, Linfócitos T

Ontology: Lymphocyte Count measurement (C0200635)

Definition (NCI) The determination of the number of lymphocytes in a blood sample.
Definition (NCI_CDISC) A measurement of the lymphocytes in a biological specimen.
Definition (MSH) The number of LYMPHOCYTES per unit volume of BLOOD.
Concepts Laboratory Procedure (T059)
MSH D018655
SnomedCT 446325007, 165535004, 142942007, 142948006, 74765001
English Lymphocyte Count, Lymphocyte Count, Total, Lymphocyte Counts, Lymphocyte Counts, Total, Total Lymphocyte Count, Total Lymphocyte Counts, Lymphocyte count NOS, Lymphocyte Count measurement, blood lymphocyte count, blood lymphocyte count (lab test), lymphocyte count, lymphocyte counts, total lymphocyte count, count lymphocytes, counts lymphocyte, lymphocyte number, count lymphocytes total, Total lymphocyte count (procedure), Total lymphocyte count, Lymphocyte count NOS (procedure), LYM, Lymphocytes, Lymphocyte Numbers, Lymphocyte Number, Lymphocyte count, Lymphocyte count (procedure)
Italian Conta linfocitaria, Numero dei linfociti, Conta totale linfocitaria, Conta dei linfociti
Swedish Lymfocytantal
Japanese リンパキュウスウ, リンパ球計数, リンパ球計算, リンパ球総数, リンパ球数
Czech lymfocyty - počet, Počet lymfocytů
Finnish Imusolumäärä
French Numération des lymphocytes, Numération lymphocytaire, Numération lymphocytaire totale, Taux de lymphocytes, Numération de lymphocytes
Polish Liczba limfocytów
Spanish recuento total de linfocitos (procedimiento), recuento total de linfocitos, Lymphocyte count NOS, recuento de linfocitos, SAI (procedimiento), recuento de linfocitos, SAI, recuento de linfocitos (procedimiento), recuento de linfocitos, recuento linfocítico, Recuento de linfocitos, Recuento de Linfocitos, Recuento Total de Linfocitos
Hungarian Limfocita szám
Norwegian Lymfocyttantall, Lymfocyttelling, Absolutt antall lymfocytter, Lymfocytt-telling
Portuguese Número de linfócitos, Contagem de Linfócitos, Contagem de Linfócitos Totais
Dutch lymfocytentelling, Lymfocytentelling, Lymfocytentelling, totale, Telling-, lymfocyten-
German Lymphozytenzahl, Lymphozytengesamtzahl, Lymphozytenzählung