MLAB Hematology Fall 2007 Keri Brophy-Martinez Unit 3: Leukocytes

NEUTROPHILS  Myelopoiesis - the production and development of myeloid cells in the bone marrow Growth factors (colony-stimulating factors - CSF’s) and interleukins regulate blood cell development by:  Mediating proliferation  Differentiation into cell lines  Maturation of hematopoietic progenitor cells

NEUTROPHILS  Three series of granulocytes (named for colors taken up by granules in Wright’s stain) Neutrophils  Granules stain equally with eosin and methylene blue  Normal in circulation = % Eosinophils  Granules stain mainly red  Normal in circulation = 0-4% Basophils  Granules stain mainly with methylene blue  Normal in circulation = 0-2%

Maturation of the neutrophilic series  Stem cell - an unspecified cell that gives rise to a specific specialized cell, such as a blood cell Multipotential and cannot be identified morphologically Can self-renew and differentiate

Maturation of the neutrophilic series  Myeloblast Size: 10-20µm Cytoplasm  Slight amount/blue  No granules ( possible Auer rods to be discussed in another section) Nucleus  Round/Central or eccentric  Reddish purple  1-3 nucleoli  Fine meshlike chromatin with no clumping N:C ratio = 4:1

Maturation of the neutrophilic series  Promyelocyte (progranulocyte) Size: 10-20µm Cytoplasm  Increased amount/blue  Fine, azurophilic, nonspecific granules present Nucleus  Round/Central or eccentric  Reddish-purple  Fine, meshlike chromatin beginning to clump  1-2 nucleoli N:C ratio = 3:1

Maturation of the neutrophilic series  Myelocyte (last myeloid cell capable of division) Size: 10-18µm Cytoplasm  Increased, bluish- pink (“dawning of neutrophilia”)  Fine azurophilic, specific granules Nucleus  Round or oval/eccentric  Reddish-purple  Chromatin loosely clumped  No nucleolus N:C ratio = 2:1 or 1:1

Maturation of the neutrophilic series  Metamyelocyte (also called “meta” or “juvenile”) Size: 10-18µm Cytoplasm  Moderate amount  Specific granules (neutrophilic, eosinophilic or basophilic) Nucleus  Indented (kidney-bean shaped)  Central or eccentric  Purple  Clumped chromatin  No nucleolus N:C ratio = 1:1

Maturation of the neutrophilic series  Band Size: 10-16µm Cytoplasm  Moderate amount  Specific granules (see meta) Nucleus  Elongated, narrow band (sausage) shape with uniform thickness  Central or eccentric  Clumped, coarsely granular chromatin

Maturation of the neutrophilic series  Segmented neutrophil, eosinophil or basophil Size: 10-16µm Cytoplasm  Neutrophil - specific fine violet pink  Eosinophil - red uniform specific granules  Basophil - coarse violet blue non-uniform specific granules (Mast cell is a tissue basophil) Nucleus  Neutrophil - purplish-red, clumped granular chromatin, 2-5 distinct nuclear lobes connected by a filament of chromatin  Eosinophil - deep blue purple, coarsely granular chromatin, 2 distinct lobes  Basophil - deep blue purple, coarsely granular chromatin, 2 nuclear lobes (sometimes obscured by cytoplasmic granules)

Maturation of the neutrophilic series

Function of the neutrophilic series  Neutrophils - defense against bacterial infections  Eosinophils Regulate inflammation Respond to antigenic stimulation in chronic allergies Interact with larval stages of some helminthic parasites  Basophils Histamine in granules plays a role in acute, systemic allergic reactions (sudden release of histamine can cause anaphylactic shock) Granules also contain heparin

MONOCYTES  Monopoiesis - the production and development of monocytes, macrophages and their precursors. Monocytes are produced in the bone marrow. Their primary function is phagocytosis.

MONOCYTES  Other names for macrophages Histiocytes in the loose connective tissue Kupffer cells in the liver Osteoclasts in the bone Microglial cells in the nervous system Also scattered throughout the body in all organ tissues (spleen, lung, abdomen, etc.) One monocytes have grown into macrophages, they do not normally reenter the bloodstream except in cases of inflammation

Maturation of the monocytic series  Monoblast Size: 12-20µm Cytoplasm  Blue, moderate amount  No granules Nucleus  Round, oval or slightly folded  Eccentric  Reddish-purple  Chromatin fine and thready  Vacuoles may be present  1-2 nucleoli N:C ratio = 4:1

Maturation of the monocytic series  Promonocyte (difficult to discern) Size: 21-20µm Cytoplasm  Paler gray-blue and abundant  “Bleb-like” pseudopods at periphery  May contain fine red “dust-like” particles  Vacuoles may be present Nucleus  Round with chromatin creases or brain-like folding  Central  Reddish-purple with light clumping of chromatin  0-2 nucleoli N:C ratio = 3:1 or 2:1

Promonocyte

Maturation of the monocytic series  Mature monocyte (Normal in circulation: 2-9%)  Size: 15-18µm  Cytoplasm Pale gray-blue and abundant Bleb-like pseudopods at periphery, variable shape Numerous fine pale red dustlike granule scattered throughout Vacuoles common  Nucleus Increased folding or elongated Central Purplish with finer clumped chromatin No nucleoli  N:C ratio = 2:1 or 1:1

Monocyte

LYMPHOCYTES  Normal adult value: 21-51%  Produced in the bone marrow (primary lymphoid tissue)

LYMPHOCYTES  Growth factors cause lymphs to differentiate. They proliferate and mature in the primary lymphoid organs:

LYMPHOCYTES  Thymus - T cells Function  Cellular immune response (they do not produce antibodies)  Regulate antibody reactions by helping or suppressing activation of B lymphs. T cells act as “helper cells” (HIV or AIDS virus causes a destruction of these helper cells), which are instrumental in aiding B cells in antibody production, and “suppressor cells”, which act as a “thermostat” to shut off the system or keep it under control. The helper to suppressor ratio is very important and is normally 2:1.  Protect against viral, bacterial, fungal or protozoan infection  Responsible for chronic organ graft rejection. (T cells have many unique antigens on their cell surfaces, some of which are the HLA - human lymphocyte antigen - markers. Cytotoxic and helper T cells act against these HLA markers if they are foreign to the host organism. HLA markers are instrumental in chronic graft rejection and that is why tissue typing is done to establish a good donor match.)

LYMPHOCYTES  Bone marrow - B cells Function  Humoral (antibody) immune response by transforming into antibody-producing plasma cells  Defense against encapsulated bacteria such as streptococci  Mediate hyperacute organ rejection

LYMPHOCYTES  Null cells - unknown maturation sequence Function  Destroy by lysis target cells (such as tumor cells) by cytotoxins  Play a role in inflammatory response  Host defense when stimulated by interferon against certain viruses (cytomegalovirus - CM, and hepatitis) by killing the virally infected target cell before the virus replicates

LYMPHOCYTES  T and B cell lymphocytes cannot be differentiated morphologically. They are distinguished functionally and by immunologic marker studies (to be discussed later.) Null cells appear as large lymphocytes with azurophilic granulocytes and are called large granular lymphocytes (LGL).

 Secondary lymphoid tissue Lymph node, spleen, Peyer’s patches in intestine and mucosal tissues such as tonsils Active immune response occurs in above tissues where lymphs communicate and interact with antigen-presenting cells, phagocytes and macrophages

Maturation sequence of lymphocytes  Lymphoblast (which is preceded by a lymphoid stem cell) Cell size: 10-20µm Cytoplasm  Blue/scanty  No granules, Auer rods are never present Nucleus  Purple, smooth chromatin  Round, central or eccentric  1-2 nucleoli N:C ratio = 4:1

Maturation sequence of lymphocytes  Prolymphocyte (difficult to distinguish) Size: 9-18µm Cytoplasm  Blue, scanty  Usually granules are absent, but a few azurophilic granules may be present Nucleus  Purple, condensed chromatin  Round or indented, eccentric  0-1 nucleoli N:C ratio = 4:1

Maturation sequence of lymphocytes  Mature lymphocyte  Cell size: 7-10µm (a typical normal lymph has a nucleus that is the size of a normal RBC)  Cytoplasm Light blue, scanty to moderate Few azurophilic granules may be present  Nucleus Purple, dense, clumped chromatin Round or indented, eccentric  No nucleoli

Large lymphocytes versus monocytes  Size Large lymph: 12-15µm Mono: 15-18µm  Nucleus Large lymph: clumped, condensed Mono: lacy, brainlike folds  Granules Large lymph: large azurophilic, easy to count Mono: red, fine  Cytoplasm Large lymph: clear, nongranular, may be indented by red cells Mono: “ground glass” appearance, projection of blunt pseudopod blebs

Maturation sequence of lymphocytes  Variant lymphs Other terms used are reactive, atypical, Downey cell, transformed, virocyte, plasmacytoid  Caused by antigenic stimulants such as viruses, post-transfusion reactions and organ transplants  General characteristics Increased size due to DNA activity in the nucleus and RNA activity in the cytoplasm Enlarged and/or monocytoid nucleus Variation in nuclear chromatin pattern Nucleus may contain 1-3 nucleoli Abundant, sometimes foamy or vacuolated cytoplasm Variation in cytoplasmic color - gray-blue to intense blue Absence of granules in cytoplasm

Reactive lymphocyte

Plasma cells  Plasma cells Function is the synthesis and excretion of antibodies (immunoglobulins) Normally not present in the peripheral blood; comprise 2% of bone marrow cells. (May be seen in the peripheral blood in the disease called multiple myeloma, a disease of uncontrolled production of immunoglobulins.) End stage of the B lymphocyte Appearance  Size: 10-18µm  Cytoplasm is dark blue with perinuclear halo and may contain vacuoles indicating antibody synthesis  Nucleus is round, eccentric, dark purple with dense clumped chromatin Variant plasma cells  Grape or Mott cell - cytoplasm completely filled with red, pink or colorless globules called Russell bodies  Flame cell - cytoplasm stains bright red-staining proteinaceous material

Plasma cells