24 August 2006
Blood
Dr. Joana Chakraborty, Ph.D.



Blood


  • Functions include: respiration, nutrition, excretion, acid-base balance, water balance, body temperature, immune defense, hormone and metabolite transport, and coagulation
  • 6%-8% of total body weight
  • Total volume approximately 5.5 L (6 quarts)
    • Total RBC volume 0.45 x 5.5 L = 2.5 L
      • i.e. RBC volume is 45% of total volume
    • Total plasma volume 5.5 L – 2.5L = 3 L
      • Remaining “liquid” portion of the blood

Plasma and Serum

  • Plasma is 93% water with 7% dissolved substances
  • Plasma = serum + fibrinogen and other clotting proteins
    • Can be separated by centrifugation of whole blood, leaving plasma as supernatant
  • Serum = plasma fibrinogen and clotting proteins
    • Plasma supernatant can be left overnight to settle to separating fibrogen and clotting factors, leaving serum as supernatant
  • Plasma is needed to determine fibrogen and clotting factors because serum does not have either.

Cellular Components of Blood


Red Blood Cells


  • Biconcave, reversible deformity
  • No mature human RBCs have nuclei or any organelles
    • Presence of immature RBCs which retain nuclei is a bad sign
  • Contains only hemoglobin
    • Oxygen-carrying protein
  • 120 day lifespan
    • Must be replaced by new cells
    • 90% of RBC dry weight

Adult Reference Ranges for RBCs

  • Average concentration of hemoglobin:
    • 13.6-17.2 g/dl in men
    • 12.0-15.0 g/dl in women
  • Average erythrocyte count:
    • 4.3-5.9 x 106/mm3 in men
    • 3.5-5.0 x 106/mm3 in women

Laboratory Studies

  • Obtain blood sample using venipuncture
    • Use vacutainers, syringes
  • Know each lab study to be performed
  • Identify additives and additive function, in color-coded top tubes
  • Precaution for HIV, hepatitis B, hepatitis C, and other blood borne infections
    • Be very careful and don’t stick yourself
    • Odds of seroconversion for HIV have been published as 400:1, but that's still significant

Hematocrit

  • Hematocrit is the estimation of packed erythrocytes per unit volume in blood
  • Normal volumes:
    • Men: 40%-50%
    • Women: 35%-45%
  • Container: Purple top evacuated tube
    • Contains EDTA anticoagulant
  • Collection: routine venipuncture; invert tube gently
  • Store at 4°C
  • Rejection if clotted or hemolyzed
  • To measure hemoglobin, follow same procedure but do not add EDTA.
    • Hemoglobin abbreviated as Hg and Hgb
    • Hemoglobin determines the oxygen carrying capacity while hematocrit only determines the RBC volume
      • Hematocrit is also predictive of hemoglobin content but a hemoglobin test would be more accurate

Spectrin

  • Human RBC membrane protein – long fibrous molecule with two polypeptide chains
  • Interacts with actin and forms a fuzzy coat inside RBC membrane
  • Allows RBC to deform as necessary, and responsible for overall stability of RBC membrane
  • Hereditary Spherocytosis – lack of spectrin, resulting in RBCs lacking deforming ability
    • Cause blood to hemolyze when they get stuck in capillaries in the spleen and people to become anemic

White Blood Cells



Neutrophil

  • Most of WBCs and have multilobed nuclui 50-70%
  • They are phagoctyes and sometimes called microphages
  • If there is a bacteria infection, neutrophils will be abundant
    • Bacteria destroyed in connective tissue spaces
  • Contains specific granules
  • In females, the inactive X chromosome appears as a drumstick-like appendage on one of the nuclear lobes

Eosinophils

  • Few in number 1-4%
  • Have a bilobed nucleus
  • Important for allergic reaction and parasitic worm killing
  • Granules contain a crystalline core and a less dense matrix

Basophil

  • Few in number <1%
  • S-shaped nucleus with large granules in cytoplasm
  • Acts as an initiator in the inflammatory process

Monocytes

  • Largest cells in circulatory blood
  • 2-8% of total leukocytes
  • When they enter connective tissue space, they are called macrophages
    • In circulation, they are monocytes
  • Produce cytokines and can present antigen to T-cells

Thrombocytes

  • 250,00 per mm3 of blood
  • Also called platelets
  • Contains no nucleus but have organelles
  • Originate from the fragmentation of the cytoplasm of giant megakaryocytes in the bone marrow
    • In peripheral area of platelets, there are lots of microtubules that act to get granules into the right place
    • During coagulation, the platlet membrane invaginates to connect to the open canalicular system, which contains the 4 granules responsible for the clotting process
      • Two Granules include:
        • serotonin --> acts as a vasoconstrictor
        • Platelet-derived growth factor --> stimulates endothelial cell mitosis

Hemopoiesis


  • Hemato means “blood,” poiein means “to make”
    • Erythropoiesis – for RBCs
    • Granulopoiesis – for granulocytes
    • Monocytopoiesis – for monocytes
    • Megakaryocytopoies – for megakaryocytes

Pluripotential Hematopoietic Stem Cells

  • Pluripotential Hematopoietic Stem Cells produce of all types of blood cells
  • Abbreviated PHSCs
  • Pluripotential – potential to differentiated into any blood cell
  • Divide continuously
    • Daughter cells are irreversibly differentiated
  • Produce two types of multipotential hematopoietic stem cells (MHSC):
    • Colony-forming unit-spleen (CFU-S) – myeloid cell line
    • Colony-forming unit lymphocytes (CFU-Ly) – lymphoid cell line

Progenitor Cells

  • Progenitor cells are daughter cells of MHSC
  • Mitotic activity and differentiation are controlled by specific hematopoietic factors
  • Limited capacity of self-renewal
    • Can undergo mitosis but cannot undifferentiated back to a PHSC

Precursor Cells

  • Produced by progenitor cells
  • No self-renewal capability
  • Undergo cell division and differentiation
  • Produce clones of mature cells
  • Each precursor cell has a unipotential colony-forming unit

Hematopoietic Growth Factors


Granulocytes


  • Colony-forming unit lymphocytes (CFU-Ly) form Myeloblast
  • Myeloblast forms promyelocytes
  • Promyelocytes produce:
    • Neurtrophilic Myelocyte
    • Eosinophilic Myelocyte
    • Basophilic Myelocyte

B-Lymphocytes

  • Produced from the bone marrow and can go directly to lymph nodes or spleen
  • Humoral immunity
  • Activated B lymphocytes produce plasma cells which actively produce antibodies specific to an antigen
  • Antibodies circulate throughout the body via blood and lymph
  • Do not interact with MHC proteins and can recognize antigen on their own

Humoral Immunity

  • Plasma cells produce antibodies which are called immunoglobulins (Ig)
  • Five-classes of Ig depending on the antigen that they have
    • IgG – 80%
      • Immunity against bacteria and viruses in the extracellular fluid
    • IgM – 5%
      • Immunity against bacteria and viruses in the extracellular fluid
    • IgA – 15%
      • Secreated by plasma cells in GI, respiratory, genitourinary tracts, and breast milk
      • Babies lack a lot of antibodies after birth and get their IgA from their mother’s milk
      • However, women infected with HIV can pass HIV to babies through breast milk
    • IgD – <1%
      • Function not clear
    • IgE – <1%
      • Defense again multicellular parasite and allergic reaction

Antibody Structure

  • Have heavy and light chain
  • Variable region of antibody allow of antibody specificity

T-Lymphocytes


Antigen Presentation

  • Marcophage must present antigen to T cells
  • Helper T cell can bind with presented antigen on MHC-II
    • MHC-II is found only on macrophages, macrophage-like cells, and B cells
      • Interacts with Helper T cells
    • MHC-I is found on all nucleated cells in the body

Roles of B cells, Cytotoxic T cells, and Helper T cells in Immune Response



Objectives