Leukocytes

What is the main function of leukocytes?

Combat invading microbes and other harmful cells; immunity role

What is Diapedesis?

• The movement of WBCs leaving the blood stream to collect at sites of invasion/infection

Ameboid Movement?

How WBC’s move through the tissue to the site of infection

What is the term used to describe the engulfing of pathogens?

Phagocytosis

Leukocytosis

• Elevation in the white blood cell count; indication of infection/inflammation

Low white blood cell count may develop into…

Several causes

What type of test helps determine if a WBC-related problem exists?

Differential white blood cell count

What are Granular white blood cells?

• WBC’s which contain vesicles; visible when cells are stained

  • Neutrophils

  • Eosinophils

  • Basophils

What are Agranular WBC’s?

• WBC’s that contain no granules

  • Lymphocytes

  • Monocytes

List the WBC’s from most to least abundant

• Neutrophils

• Lymphocytes

• Monocytes

• Eosinophils

• Basophils

Neutrophils

• Most numerous WBC

• Nucleus has 6 lobes

• Travel to tissues and acts as a phagocyte at infection site

• Attracted by bacterial products

• First line of defense in inflammatory response

• Dead neutrophils, cell debris, fluid → accumulate as pus

• Release enzymes into ECM of infected tissue

What is pus?

Substance comprised of the accumulation of dead neutrophils, cell debris and fluid

Eosinophils

• Granules contain enzymes active during allergic reactions and parasitic infections

• end allergic reactions via phagocytizing allergens and releasing enzymes that degrade histamines to reduce inflammation

• Fight parasites via attaching to them and releasing enzymes that kill them

Basophils

• Nucleus has two lobes

• Secrete histamines and other chemicals which promote inflammation

• Function in inflammation mediation; direct later stages of inflammation in allergies

Lymphocytes

• most important cells of the immune system

• Effective in fighting infections organisms

• Fights against specific foreign molecules (antigens)

What is the most important cell of the immune system?

Lymphocytes

What are the two main classes of lymphocytes? What do they do?

• T cells

  • Attack foreign cells directly

  • Several types with diverse functions

    • Reject grafts

    • Kill virus-infected cells

    • Control tumors

    • Regulate immune system

• B Cells

  • Multiply to become plasma cells

  • Secrete antibodies which attack foreign antigens

Monocytes

• Largest of the leukocytes

• Transform into macrophages while traveling to infection site

• Phagocytic cells; arrive to site as neutrophils start to die off

• Present antigens to lymphocytes during specific immunity

Which leukocyte presents antigens to lymphocytes during specific immunity?

Monocytes

Percentage of Neutrophils in total WBCs

60-70%

Percentage of Lymphocytes in total WBC’s

20-25%

Percentage of Monocytes in total WBC’s

3-8%

Percentage of Eosinophils in WBC’s

2-4%

Percentage of Basophils in total WBC’s

0.5-1%

Describe the process of platelet/thrombocyte formation

• The hormone thrombopoietin causes stem cells to differentiate into megakaryocytes

• In red bone marrow: Megakaryocytes splinter into 2000-3000 fragments to create platelets