1

White blood cells often have irregularly shaped

nuclei.

65% of white blood cells are granular leucocytes as

they have granules in their cytoplasm. They are

formed in the bone marrow.

35% have no granules and are agranular. They are

formed in the lymph nodes, spleen, tonsils and

thymus.

White Blood Cells Blood

granular leukocytes agranular leukocytes

White Blood cells FeaturesPlace of

production

Lymphocytes •Contains large central nucleus

•Non-granular cytoplasm

•Produces antibodies

•Involves in tissue rejection and killing of tumor cells.

Lymph nodes

Lymph glands

Bone marrow

Phagocytes •Contains lobed nucleus.

•May be granular or non granular.

•Ingest foreign particles (e.g. bacteria) by phagocytosis

Bone Marrow

3

Phagocytes are white blood cells with lobed nuclei.

They ingest solid particles such as germs, and digest them.

When the body is infected, phagocytes move to the site of

infection, and ingest and digest the germs.

Phagocytosis is a process by which the cell membrane

engulfs a food particle and brings it into the cell.

White Blood Cells Blood

pseudopodium

bacteria

4

Lymphocytes are white blood cells with a single nucleus

which is roughly spherical in shape.

They secrete globulins known as antibodies.

Each antibody is specific.

When antibodies remain in the body, the body is said to be

immune to a specific disease.

The body would have developed natural active immunity if

the microbes enter the body through natural means.

When a person has been vaccinated, the immunity is

artificial active immunity.

White Blood Cells Blood

Pathogens in blood Toxins in blood

Lymphocytes

Antibodies Antitoxins

Agglutinate

bacteria

Destroy

bacteria

Attach to virus

Attaching to bacteria

& causing its

membrane to rupture

Clumping of

bacteria for more

efficient

phagocytosis

So that it

cannot bind to

host cell

Neutralise toxins

in blood

produce

stimulate

produceproduce

Act on Act on

Functions of antibodies

• Clumping of bacteria

• Attachment to protein

coat of virus

▫ Prevents virus from

being transported

▫ Prevents virus from

attaching to a host for

replication

Immunity

Antibodies remain in blood long after disease has been overcome

To prevent the patient from suffering the same disease again

Immunizations

Inject small amount of dead/inactivated bacteria

Stimulate lymphocytes to produce antibodies against bacteria

Inject dead bacteria into animals to induce formation of antibodies in them. Antibodies are then injected into humans

Organ transplant

If donor tissue/organ comes from same person

Tissue will not be rejected as cells have the same antigens

from the same donor.

Tissue rejection may occur when tissue comes from

another donor

Cells may be treated as foreign body and donor’s

lymphocytes may produce antibodies

Preventing tissue rejection

1. Matching of donor and recipient tissue

Tissues must be as genetically close as possible

Eg: Relatives should have more similar genes

2. Use immunosuppressive drugs to inhibit recipient’s immune system

Disadvantages:

Lower resistance to many other infections

Has to take drugs for the rest of his life

A white blood cell being attacked by the HIV virus.

Immune system being destroyed by the virus.