Module 4: Hematopoiesis (Lymphoid and Monocytic Series)

lymphocytes and plasma cells

are white blood cells that cooperate in defending the body against disease

• recognition of foreign antigens

• antibody production (specifically for plasma cells)

Lymphocytes and plasma cells are white blood cells that cooperate in defending the body against disease through:

• T-lymphocytes

• B-lymphocytes

• Natural killer (NK) cells

lymphocytes major groups

unique cell surface markers present on each type of the lymphocyte

Classification is based on?

NK cells

directly derived from the common lymphoid progenitor stem cell

Lymphocytes

resting cells and when stimulated, undergo mitosis to produce memory and effector cells

lymphocyte recirculation

Lymphocytes move freely between the blood and lymphoid tissues

30% of the total leukocytes

total blood lymphocytes at birth

34% of the total leukocytes

total blood lymphocytes in adults

approx. 5% of the total body lymphocytes

total body lymphocytes present inthe circulating blood in normal adults

antigen-sensitized memory lymphocytes

It enables lymphocytes to come into contact with foreign (blood-borne) antigens in the blood and to disseminate?

60-80%

% of T lymphocytes

20%

% of B lymphocytes

4-29%

% of NK cells

pluripotent precursor cells

During embryonic development, lymphocytes arise from?

interleukin-1 (IL-1) and interleukin-6 (IL-6)

growth factors that influence differentiation of the pluripotent stem cells into lymphoid stem cells

CENTRAL / PRIMARY Lymphatic Organs

• Bone Marrow

• Thymus

Thymus

located in the upper anterior chest area, known as the anterior mediastinum

PERIPHERAL / SECONDARY Lymphatic Organs

• Spleen (Left upper quadrant of abdomen)

• Lymph nodes

• Tonsils

• Mucosa-Associated Lymphoid Tissue (MALT) like Peyer’s patches in the intestines

• Pro-B cell (progenitor B-cell)

• Pre-B cell (precursor B-cell)

• Immature B cell

stages seen in bone marrow

Plasma Cells

• most prominent effector cell

• are fully differentiated B lymphocytes that are able to produce antibodies or immunoglobulins specific to the offending antigen

CD138

most widely known specific cell surface marker of plasma cells

CD (cluster of differentiation)

certain markers are shared among the stages and some are unique to each stage and these are used to identify them

Pro-B-Cell

CD34+

TdT+

CD22+

CD38high

CD45low

Pro-B-I-Cell

CD34+

TdT+

CD22+

CD38+

CD19+

CD79a+

CD10high

CD45low

Pro-B-II-Cell

CD20

CD22+

CD38+

CD19+

CD79a+

CD10low

CD45high

cyIgμ

Immature-B-Cell

CD20+

CD22+

CD38+

CD19+

CD79a+

CD10low

CD45high

cyIgμ

IgM

Mature-B-Cell

CD20+

CD22high

CD19+

CD79a+

CD45high

IgM/IgD

CD4+ T lymphocytes (T helper cells)

As soon as they are activated, they secrete substances that

help B lymphocytes differentiate into memory and effector cell.

CD8+ T lymphocytes (T cytotoxic cells)

Secretes substances that kill the target cell (like the action of NK cells)

Human Immunodeficiency Virus (HIV)

Targets the CD4+ T lymphocytes

cell surface markers, Pro, Pre and Immature T cells

Resting B Lymphocytes and resting T Lymphocytes can only be distinguished by?

1 Lymphoblasts

2 Prolymphocytes

3 Mature Lymphocytes

4 Plasma cells

Based morphology, the lymphoid series cells are

classified as:

Lymphoblast

The earliest / first morphologically identifiable cell of the lymphocytic maturational series in the bone marrow

10-22 μm

size of lymphoblast

Nucleus of Lymphoblast

Shape: Round or oval, centrally or eccentrically placed

N:C Ratio: 7:1 to 4:1

Color: Reddish-purple

Chromatin: Fine, lacy pattern to moderately coarse

Nucleoli: 1-2 prominent (less prominent than myeloblast)

Cytoplasm of Lymphoblast

Color: Moderate to dark blue

Contents: Smooth, no granules, occasional vacuoles

Prolymphocyte

May be seen in the bone marrow, thymus, and secondary lymphoid tissues

size of Prolymphocyte

Overall size is similar to the lymphoblast (15-18 μm)

Nucleus of Prolymphocyte

Shape: Usually oval or slightly indented

N:C Ratio: 4:1 to 3:1

Color: Reddish-purple

Chromatin: Highly condensed (More condensed than lymphoblast)

Nucleoi of Prolymphocyte

Nucleoli: Varies from none, one, or two

Color of Prolymphocyte

Medium blue with a thin, darker blue rim;

Prolymphocyte contents

Few azurophilic granules may be present (more cytoplasm than

lymphoblast)

Mature Lymphocyte

Should be the only lymphoid cell that is normally seen in a blood smear.

Resting lymphocytes

are usually small, their size approximates that of a normocytic red blood cell (often 7-8 μm in size)

size of Mature Lymphocyte

7-15 μm (nucleus is comparable in size than the normal RBC)

nucleus of Mature Lymphocyte

Shape: Round or slightly indented, eccentric

N:C Ratio: 3:1 (can be 2:1)

Color: Deep purple-blue

Chromatin: Course and clumped; heavily condensed

Nucleoli: None visible

cytoplasm of Mature Lymphocyte

Color: Sky blue to deep blue

Contents: Scant and usually nongranular; few azurophilic granules may be seen

Variant/Reactive Lymphocyte

• Present in viral diseases including infectious mononucleosis, cytomegalovirus, toxoplasmosis, hepatitis, and cat scratch fever

• mistaken for immature lymphoblasts or prolymphocytes

antigenically stimulated lymphocytes

have increased DNA and RNA activity

nucleus of Variant/Reactive Lymphocyte

Shape: Oval, notched, indented, or elongated (may be lobulated or resemble the nucleus of a monocyte with clefts or notching and may be folded)

Nucleoli: 1 or more large nucleoli may be visible

color of Variant/Reactive Lymphocyte

• Often abundant and stains pale to deep blue and darker at periphery

• Cytoplasmic color may range from gray to light blue

  or intensely blue

Variant/Reactive Lymphocytes contents

May be partially indented by adjacent red cells; few lavender granules and/or vacuoles

16-30 um

overall increased size of Variant/Reactive Lymphocyte

Plasma Cell

• Fully differentiated B Lymphocyte

• Not normally found in the circulating blood but are seen in the bone marrow in concentrations that do not normally exceed 2%.

• Arise as the end stage of B-cell differentiation after antigenic stimulation

size of Plasma Cell

Overall size: 14 to 20 μm

active production and secretion of proteins, mainly antibodies

What does the distinctive dark blue with visible lighter staining area in the nucleus of plasma cells indicates?

Russell bodies

(small globules within the cytoplasm) which are acidophilic, refractile globules that represent gamma globulin (protein) secretions

most striking feature of Plasma Cell

• Nucleus is small and eccentrically-located (almost peripheral)

• Chromatin is condensed and has a cartwheel configuration

Monocytes

are white blood cells (leukocytes) that function mainly as phagocytes in blood and in tissues, where they become macrophages.

2% to 11% (absolute number of up to 1.33 x 109 /L)

% of monocytes of circulating leukocytes

Kupffer Cells

Liver

Alveolar macrophages

Lungs

Microglia

Brain

Langerhans cells

Skin

Splenic macrophages

Spleen

Intestinal macrophages

Intestines

Peritoneum

Peritoneal macrophages

Osteoclasts

Bone

Type A cell

Synovial

Renal macrophages

Kidneys

Dendritic cells

Lymph nodes

Innate Immunity

Recognition of bacterial pathogens, synthesize and secrete cytotoxic agents (nitric oxide)

Adaptive Immunity

Recognition of bacterial pathogens, synthesize and secrete cytotoxic agents (nitric oxide)

“Housekeeping” cells

With removal of cell debris and dead cells from area of infection and tissue destruction/injury

• Innate Immunity

• Adaptive Immunity

• “Housekeeping” Cells

functions of Monocytes

granulocytemonocyte progenitor (GMP)

Where are monocytes derived from?

Macrophage colony-stimulating factor (M-CSF)

major cytokine responsible for the growth and differentiation of monocytes

morphologic stages of the monocyte development

1 Monoblasts

2 Promonocytes

3 Monocytes

mature monocytes

are normally found in peripheral blood, the rest are seen in the bone marrow.

Pseudopods

are frequently seen at any stage at the monocytic development, but it is common in mature monocyte stage. It sometimes aid in phagocytosis and movement.

Monoblast

Only normally found in the bone marrow but even then, are rarely seen.

Size: 14-20 μm (large in comparison with RBCs)

Monoblast nucleus

Shape: Round or oval

N:C Ratio: 3:1 to 1:1

Color: Light bluish-purple

Chromatin: Fine and distinct

Nucleoli: 1-5

Monoblast cytoplasm

Color: Blue - gray

Contents: No granules (agranular)

Promonocyte

• Vacuoles are more commonly seen than in monoblast

• Granules are giving an impression of a ground-glass

appearance.

Size: 12-18 μm (large in comparison with RBCs)

Promonocyte nucleus

Shape: Nucleus is slightly indented or folded (more than monoblasts)

Color: Light bluish-purple

Chromatin: Delicate

Nucleoli: Less prominent nucleoli (than monoblasts)

Nucleolus: At least 1 apparent

Promonocyte cytoplasm

Color: Blue and contains scattered azure granules that are fewer and smaller than those seen in promyelocytes

Contents: No granules (agranular)

Mature Monocyte

Can be considered as slightly immature cells whose ultimate goal is to enter the tissues and become macrophages

Mature Monocyte nucleus

Nucleus: round, oval, or kidney-shaped but more frequently deeply indented (horseshoe-shaped) or folded on itself (irregular-shaped)

Chromatin: loose (than other leukocytes), described as fine, ‘lacelike’

Mature Monocyte cytoplasm

• Blue-gray cytoplasm with fine azure granules or ground glass appearance

• Small cytoplasmic pseudopods or blebs and vacuolations are commonly seen

immature B cells

antigen naive cells

hof

dark blue with a visible lighter staining area around the nucleus