White Blood Cells

Question 1

leukocytes

Answer 1

• white blood cells
• are mobile units of the body’s protective system.
• formed partially in the bone marrow (granulocytes and monocytes and a few lymphocytes) and partially in the lymph tissue (lymphocytes and plasma cells)
• after formation they are transported to diff locations in the blood
• areas of serious infection and inflammation thereby providing a rapid and potent defense against infectious agents.

general characteristics
- types of white blood cells
• six types : polymorphonuclear neutrophils, polymorphonuclear eosinophils ,polymorphonuclear basophils, monocytes and lymphocytes and occasionally plasma cells.
- first 3 granular appearance hence called granulocytes
- granulocytes and monocytes protect the body by phagocytosis or by releasing antimicrobial or inflammatory substances
- lymphocytes and plasma cells function mainly in connection with the immune system
- adult human - 7000 wbc / microliter of blood
- neutrophils - 62%
eosinophils - 2.3
basophils - 0.4
monocytes 5.3
lymphocytes 30

Question 2

genesis of leukocytes (leucopoiesis)

Answer 2

two Lineages - myelocyctic and lymphocytic

• these develop fr colony forming unit spleen (CFU-S)
• and the common myeloid progenitor cell is colony forming unit granulocytes monocytes (CFU-GM) or the common myeloid progenitor (CMP)
• these are also collectively named as colony forming unit granulocytes erythrocytes monocytes megakaryocytes CFU-GEMM
• factors that promote the differentiation of CFU-GM into neutrophils eosinophils basophils and monocytes include the granulocyte-macrophage colony stimulating factor GM-CSF
• G-CSF
• M-CSF
• along with interleukins IL 3,5,11
• wbc in the bone marrow are stored within the marrow until they are needed in the circulatory system. normally about 3 times as many wbc are stored in the marrow - 6 days supply of these cells

Question 3

neutrophils and macrophages

Answer 3

• mainly them that attack and destroy invading bacteria, viruses and other infectious agents.
• the macrophages begin life as monocytes which are immature in blood and have little ability to fight infectious agents at that time. however once they enter tissue they begin swelling - sometimes fivefold
• 10-20 hrs in blood
• once in tissues - can live for months

Question 4

functions of neutrophils

Answer 4

Neutrophils attack and destroy invading bacteria. Various stages involved are:
1. Margination: Neutrophils stick to endothelial cells of blood vessels.
2. Diapedesis : They squeeze through gaps between endothelial cells and enter tissue spaces.
3. Chemotaxis: They are chemically attracted towards bacterial toxins, complement C5,etc.
4. Phagocytosis : On reaching the bacteria neutrophils engulf them. Phagocytosis is facilitated by rough
surface of particle, loss of protein coat and by opsonins like IgG, complement C3,etc.
5. After phagocytosis, Bacteria are killed and digested by the enzymes like myeloperoxidase with formation of
lethal ions like superoxide, hypochlorite ions, etc.
6. Lactoferrin secreted by neutrophils inhibits bacterial growth and also multiplication of CFU-GM cells thus
controlling neutropoiesis.

Question 5

functions of wbc

Answer 5

neutrophils - endothelial adhesion, chemotaxis, phagocytosis, antibacterial compounds in granules

eosinophils - interaction with t lymphocytes in allergy, helminth larvicidal

basophils - inflammation, initiation of tissue repair after injury

t lymphocytes - cellular immunity (helper, memory and cytotoxic)

b lymphocytes - humoral immunity (plasma cells secreting immunoglobulins)

monocytes - immunoregulatory - antigen presenting cells, phagocytosis, chemotaxis

Question 6

physiological and pathological variation

Answer 6

physiological -

• age - infant 20,000 / mm3
  - children - 10,000 - 15,000
  - adult - 4000 -11,000
• sex - male> female slightly
• diurnal - max in afternoon and min in early morning
• exercise - slight inc
• sleep - dec
• emotional condition (anxiety) - inc
• pregnancy - inc
• menstruation - inc
• parturition - inc

pathological
- leukopenia - dec below 4000
• anaphylactic shock
• cirrhosis
• disorders of spleen
• pernicious anemia
• typhoid and parathyphoid
• viral infection
- leukocytosis - inc above 11,000
• infection
• allergy
• common cold
• tuberculosis
• glandular fever
- granulocytosis - abnormal inc in granulocytes
- granulocytopenia 
- agranulocytosis/agranulosis/ granulopenia - acute pathological condition. characterised by absolute lack of granulocytes particularly neutrophils
- leukemia - tlc > 50,000

Question 7

properties of wbc

Answer 7

• diapedesis
• ameboid movement (neutrophils, monocytes and lymphocytes)
• chemotaxis
• phagocytosis (neutrophils and monocytes)