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Major functions of leukocytes and platelets

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Leukocytes- White blood cells, use circulation for transport

Travel near the capillary wall and invade tissue space to fight infection. They are classified by structure and

There are many different types

- they have multi lobed nuclei with many granules

/ Neutrophils - phagocytic and the

abundant leukocyte

/ Eosinophils - Allergic response

/ Basophils- Produce

Lymphocytes- These are the antibody producing cells of the body

Monocytes- Phagocytic

Polymorphonuclear granulocytes are first on the scene during an immune response, they adhere to blood vessel in infected are and migrate to tissue, they engulf, kill and

microorganisms. They also release inflammatory mediators.

B-lymphocytes - Mature in bone marrow, responsible for

(antibody-mediated) immunity. When they encounter a foreign antigen, they initiate production of

Antibody-antigen reactions assist phagocytosis by precipitation,

(clumping) or coating in antibody-

The primary immune response: first exposure, antibodies appear after latent period, peak then fall

Secondary immune response is greater, quicker and larger response due to memory B cells

Passive immunity is achieved by injecting immunoglobulins or across the placenta

T lymphocytes - dependent on the

derived in bone marrow and migrate there, acquire surface antigenic molecules and become immunologically competent. They're responsible for

immunity (not antibodies). They circulate in the blood and if they encounter a foreign antigen, they undergo blast transformation and their progeny have receptors complimentary to the antigen that was encountered. These are called

T-lymphocytes. They secrete

(attract macrophages), lymphotoxin (kill cells) and interferons that kill

There are many types: cytotoxic T cells (CD8+), Helper T cells (CD4+) and suppressor cells

Monocytes- Large, singular horse-shoe nucleus. Appear after granulocytes, once in the tissue they become

They engulf microorganisms, tissue debris and dead polymorphs. They also secrete inflammatory mediators and stimulate angiogenesis. They ingest and store

Normal leukocyte count: Neutrophils (40-75), Lymphocytes (20-45), Monocytes (2-10), Eosinophils (0.04-0.4), Basophils (0.01-0.1)



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