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Lecture 2White Blood Cells(Leucocytes)

*1- Describe the white blood cells in terms of their:CountTypesSite of formationLife spanFunctions2- Describe abnormal leukocyte count (leucocytosis, leucopenia and leukaemia)?.3- Define immunity and its different types ?.Lecture Objectives

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*White blood cells WBCs: motile units of the body's protective system. Carrying their function outside blood vessels. Normal count in adult is 4000-11,000 /mm3In infants, total count is 20,000 /mm3In children, neutrophils 40%, lymphocytes 45%

*White blood cells

Less than 4000/mm3 = LeucopeniaMore than 11000/mm3 = Leucocytosis = inflammationLeucocytes are larger than RBCs

*Types:

1- (multi-nuclear or "polys") = Granulocytes They show granules under Microscope that contain needed materials for their activity. Neutrophils 62 % (in children 40%) Eosinophils 2.3 % Basophils 0.4 %

2- Mononuclear = A granulocytesLymphocytes 30 % (in children 45%) Monocytes 5.3 %

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*Site of formationAll leucocytes in bone marrow except lymphocytes .

Most lymphocytes in lymph tissue (lymph glands, spleen, thymus, tonsils) & few in bone marrow (from bone marrow precursor cells called -Blast).

*Site of formationLymphocytes that formed in Thymus are called T-Lymphocytes .

Lymphocytes that formed in Bone marrow are called B-Lymphocytes.

Vit. B12 and Folic acid are needed for Leucopoiesis (WBCs formation).

*Haemopoiesis Stages in development of blood cells

*Life spanGranulocytes: (N,E,B) 4 - 8 hours in blood, 4 - 5 days in tissues.

Monocytes: 24 -36 hours inside blood but, when they become macrophage its life span will be months in tissue (tissue macrophages).

Lymphocytes: weeks or monthsOthers lymphocytes for many years as T-lymphocytes (memory cells).

*Neutrophils and Macrophages (Monocytes) defend against infections

*PhagocytosisDefinition: Cellular ingestion of the offending agent.Most important function of neutrophils and macrophages.Selective process.Phagocytosis is increased if :Surface of particle is roughLacks protective protein coatBinding of antibodies to antigen (opsonization)

*Phagoytosis by neutrophilsAlso called polys: first line of defense in bacterial infections.

Mature cells that can attack and destroy bacteria even in the circulating blood.

The primary function of neutrophils is phagocytosis.

*Phagoytosis

*Phagocytosis by monocytes 2-8%The second line of defenceLargest WBCs & large amount of cytoplasmImmature in blood (1-2 days)They mature and enlarge in tissues to become tissue macrophages.

*Phagocytosis by monocytes 2-8%Much more powerful phagocytes than neutophils.They cross capillary wall to the tissues and become Tissue Microphage.They migrate in response to chemotaxic stimuliCan engulf large particles e.g. malarial parasites.

*Monocytes life span-Normally 1-2 days.

-But when it becomes macrophage, life span will be months to years.

-So the number of macrophage in tissues is about 400X the circulating monocytes.

-Examples of tissue macrophage:1-Kupffer cells in liver2-Mesangial cells in Kidney

*Neutrophils and Monocytes reach the site of infection by the following mechanisms:

They squeeze through the pores of the capillaries by diapedesis.They move toward the site of infection by amoeboid movement.Different chemicals released by microbes and inflamed tissues attract neutrophils and macrophages chemotaxis.

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*Types of chemotaxis+ ve chemotaxis

- ve chemotaxis

*Types of chemotaxis+ ve chemotaxisSubstance secreted by bacteria leads to attraction of neutrophils.

*Types of chemotaxis - ve chemotaxisSubstance secreted by bacteria leads to repulsion of neutrophils.Pus = Dead neutrophils

* NeutrophiliaIncrease the number of neutrophils.As in infection or tissue damage.NeutropeniaDecrease the number of neutrophils.As in Depression of BM (bone marrow) or excessive use of antibiotics

*Basophils 0.5% Similar to mast cells outside capillaries in connective tissue.

Both basophils and mast cells release heparin into blood, which prevent blood coagulation.

Play a role in allergic reactions. When ruptured histamine and other substances released cause local vascular and tissue reactions that are characteristic of allergic manifestations.

*Eosinophils 2%

Produced in large numbers in persons with parasitic infections.

They attach themselves to the surface of the parasite .

Release substances that kill the invading parasite.

*Eosinophils 2%

Release of eosinophil chemotactic factor from mast cells and basophils make them collect in tissues in which allergic reaction has occurred prevent the spread of the inflammatory process (detoxify substances and destroy Ag-Ab complexes).

*Abnormal leukocyte counts

Leucopoenia: is a decrease in WBC count (as occurs in bone marrow depression).

Leukocytosis: is an increase in WBC count above normal.

*Leukocytosis

Leukocytosis: is an increase in WBC count above normal. Neutrophilia occurs in bacterial infections and tissue damage (e.g. myocardial infarction).Eosinophilia occurs in allergic conditions and parasitic infestation.Basophilia occurs in allergic conditions.

*1 minute QuizWhat changes would you expect to find in the blood of a patient with acute bacterial infection e.g. tonsillitis?

*Leukaemia

A malignant disease of the bone marrow or lymphoid tissue in which there is uncontrolled proliferation of white blood cells.

*Leukaemia

It is characterized by a very high WBC count (may reach to 500,000/mm3) but these cells are non-functioning and hence the subject is prone to infections.

*ImmunityDefinition: The ability of the body to resist all types of organisms or toxins that damage the tissues.

Types:Natural (innate)Acquired

*ImmunityTypes:Natural (innate): general protective mechanisms e.g. phagocytosis, acidic secretion and digestive enzymes of the GIT, resistance of the skin to invasion, etc...

Acquired: the ability to develop powerful protective mechanisms against specific invading agents e.g. lethal bacteria and viruses.

*Types of Acquired ImmunityHumoral or B-cell immunity.

Cell mediated or T-cell immunity.

*Types of Acquired ImmunityHumoral or B-cell immunity: involves the development of circulating antibody(Ab) that are capable of attacking an invading agent.

*Types of Acquired ImmunityCell mediated or T-cell immunity: is achieved through the formation of large numbers of activated lymphocytes that are specifically designed to destroy the foreign agent.

*Lymphocytes 30%No phagocytosisLymphocytes are responsible for acquired immunity. They are present in lymph nodes and other lymphoid tissues throughout the body.

*Lymphocytes 30%B lymphocytes: formed in bone marrow. When exposed to an Ag plasma cells antibodies (IG)-gamma globulins) destruction of the antigen (humoral immunity = antibody formation).

*Lymphocytes 30%

T lymphocytes: formed in thymus. They release chemicals that destroy target cells such as virus infected cells and cancer cells & rejection of transplanted organs (cell mediated immunity).

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*SummaryWhat are the different types of WBCs?What is their count and percentage?What is their role in protecting the body against infections?What is leucocytosis? Causes.What is leucopenia? Causes.What are the different types of immunity?What role do lymphocytes play in acquired immunity?