Histology                                                                                                         Stanley Shostak
BioSc 1450                                                                                                      Spring 05

Lecture 4. Blood

formed elements: leucocytes (white blood cells) and lymphocytes , erythrocytes (red blood cells), platelets
plasma (translucent, yellowish, viscous)

serum: portion of plasma that separates from coagulum after clotting

blood smear:

Romanowsky-type staining
Giemsa, Wright or Leishman hemoglobin of RBCs - eosinophilia
Granules basophilia (blue): methylene blue: azurophilia (purple) lysosomes eosinophilia (pink)
neutrophilia (salmon pink/lilac) RBC (erythrocytes): anucleate corpuscles in adult mammals (nucleate cells in embryonic and fetal mammals and other vertebrates)

'yardstick' for estimating dimensions of other cells in sections, i.e., = about 7 micro m in diameter. erythron (census): whole mass of RBCs & their precursors in bone marrow
cytoskeleton: cortical meshwork: spectrin
lifespan: 120 days
Reticulocytes: release form; 1% circulating RBCs; supravital staining: brilliant cresyl blue on fresh blood > reticular precipitate (rRNA); after
hemorrhage or hemolysis: reticulocytosis > increase reticulocyte count WBC: (white blood cells  = leucocytes: recently confined to granulocytes, mononuclear leucocytes (use blood as vehicle for transport but perform roles in connective tissue); platelets = thrombocytes; traditionally included lymphocytes as well  (lymphocytes now generally considered part of lymphatic system although produced by same pleuripotential (hematopoietic) stem cell in bone marrow and use blood as vehicle) Granulocytes = myeloid tissue (bone marrow)
  neutrophils = polys (polymorphonuclear granulocytes; also known as microphage [phagocytize 'microbes']) 40 to 75% of circulating leucocytes (differential white cell count); 12 to 18 micro m in diameter but generally smaller than eosinophils; Barr body - drumstick chromosome visible in about 3% peripheral blood of females; condensed chromatin = low rate transcription; pus cells; hexose monophosphate pathway generates oxidants (hydrogen peroxide); glycolysis occurs in poorly oxygenated environment. attracted by chemotaxins (e.g., C5a) released from damaged tissue; phagocytic activity enhanced by opsonization: coating of antibodies & complement; motile and endocytotic; phagosome = endocytotic vesicle; neutrophil stimulation: binding complement fraction C5a to receptors > degranulation, hydrogen peroxide and superoxide locally; die after engulfing bacteria (do not reenter circulation)

Granules

3 types:
(1) primary: azurophilic granules: large lysosomes; primary granules; myeloperoxidase: microbicidal agent; identifies leukemias of neutrophil precursors.

(2) secondary (specific) granules: smaller, twice as numerous; alkaline phosphatase = phosphasome (light fraction of membranes)

(3) tertiary: contain gelatinase; enhance phagocytosis

neutrophilia: cite of bacterial infection attract neutrophils > increased numbers in circulation
 

 eosinophils: 1-6% differential white cell count; diurnal variation (greatest in morning; least in afternoon); 12 to 18 micro m in diameter; generally larger than neutrophil; bilobed nucleus hidden by granules; some ER and mitochondria; phagocytic but less microbicidal than neutrophils; affinity for antigen-antibody complexes.
circulate  3 to 8 hours before entering skin or mucosa of lung or gut; may migrate into local secretions; attracted by substances released by basophils and mast cells (histamine and eosinophil chemotactic factor of anaphylaxis [ECF-A]) and activated lymphocytes; degranulate in presence of large parasites (helminthes = worms]; probably do not re-enter circulation.

receptors for IgE; produce eosinophil-derived-inhibitor; inhibits mast cell degranulation; inhibits SRS-A (vasoactive substance produced by basophils and mast cells).

Granules

specific: bright red with eosin & more brick red with Romanowsky; contain variety of hydrolytic enzymes including histaminase; crystalloid lattice consists of extremely alkaline major basic protein; hydrolytic lysosomal enzymes and peroxidase

smaller granules: contain aryl sulfatase (secreted independently of degranulation; function unknown) and acid phosphatase

eosinophilia: parasitic disease; numbers also increased in some allergic disorders (hay fever & asthma).

  basophils: < 1% differential white cell count; 8 to 10 mm in diameter; bilobed nucleus hidden by granules; free ribosomes, mitochondria, glycogen; blunt irregularly spaced projections. receptors for Fc segment of IgE (produced in response to allergens); forms bridges between adjacent IgE molecules; triggers rapid exocytosis of granular contents (degranulation);

immediate hypersensitivity (analphylactoid) reaction: caused by rapid degranulation and release of histamine and other vasoactive mediators; characteristic of allergic rhinitis (hay fever), some forms of asthma, urticaria, and anaphylactic shock

up to 15% infiltrating cells in allergic dermatitis and skin allograft rejection = cutaneous basophil hypersensitivity induced by sensitized lymphocytes; degranulation slow.

Granules

specific: highly soluble in water; metachromatic with toluidine blue; proteoglycans: sulphated glycosaminoglycans: heparin & chondroitin sulphate; histamine & slow reacting substances of anaphylaxis (SRS-A), eosinophil chemotactic factor of anaphylaxis (ECF-A).

smaller granules: near nucleus

Mononuclear leucocytes = agranulocytes (not strictly speaking, i.e., contain azurophilic granules)
monocytes: up to 20 micro m; 2 to 10 % differential white cell count; highly motile and phagocytic; precursor of tissue phagocytes; nucleus less dense than lymphocytes; deeply indented > horseshoe shape nucleus enclosing golgi apparatus and centrosome; nucleoli present; pale grayish blue cytoplasm with Romanowsky; small pink to purple stained lysosomal granules; cytoplasmic vacuoles (frosted glass) necrotaxis: migration into tissues; engulf and destroy tissue debris & foreign material

mononuclear phagocyte system: monocyte-macrophage system (histiocytes); multinucleate giant cells; hepatic macrophages (Kupffer )cells; microglia of CNS;  macrophages (Langerhans cells) of skin; antigen-presenting cells (APCs) of lymphoid organs; osteoclasts of bone.

Granules

lysosomes: acid phosphatase, aryl (axurophilic) granules (of neutrophils)
secondary granules of unknown function:
  
Lymphocytes (B and T cells): 20 to 50% differential white cell count; increased numbers during viral infection; round, densely stained nucleus, small amount pale basophilic; no nucleoli visible in lt microscope due to nuclear basophilia; cytoplasm with free ribosomes; short microivilli (seen in EM) more numerous on B lymphocytes than T lymphocytes; only blood (lymphoid) cell capable of division outside of bone marrow.
small: 6 to 9 micro m: 3% of lymphocytes in peripheral blood (also medium) large: 9 to 15 micro m: possibly natural killer cells; possibly dividing lymphocytes
 directed against foreign antigen; key roles in immune response
Platelets (thrombocytes):  homeostasis: control of bleeding: 150,000 to 400,000/ml; round or oval, biconvex discs, 1.5 to 3.5 micro m; cytoplasm purple-staining, granular; organelles concentrated toward center; granules constitute about 20% volume

Granules (4 types)

Alpha granules: contain two platelet exclusive proteins: platelet factor 4; b thromboglobulin (function unknown); also coagulation factors (fibrinogen, factor V, factor VIII/ von Willebrand factor) fibronectin, thrombospondin, platelet-derived growth factor), other growth factors.

Dense granules: contain serotonin absorbed from plasma (from enterochromaffin cells of gut)

Lysosomes:

microperoxisomes: peroxidase activity, probably catalase.

Plasma membrane: ability to form fibrillar bridges between platelets; attached to thick, filamentous glycocalyx; high concentration of external membrane proteins.

Marginal band of microtubules; rich in actin and myosin (thrombostherin)

Dense tubular system (DTS): narrow membranous tubules containing isoenzyme of peroxidase specific for platelets (site prostaglandin synthesis?)

external pits connected to canalicular membrane system: (secretion of alpha granules?)

 plasma proteins albumins (bulk): bind and transport
globulins: alpha, beta and gamma
lipoproteins
blood coagulation proteins: prothrombin, fibrinogen (gives rise to fibrin) last revised: 01-15-05