Ch 5 Leukocytes

Leukocyte

White blood cell

Leukogram

assess # and morphological features of WBC in perpihreal circulation

• helps classify pathologic process

  • not specific diagnosis

Mononuclear

• round nuceli

Polymorphonuclear (PMN’s)

• granulocytes

  • lobulated nucleus

Granulocytes

neutrophil, eosinophil, basophil

Neutrophil

• most numerous leukocyte in domestic animals

• first line of defense

  • cytoplasmic granules stain neutral

Mature neutrophil

segmented nucleus with condensed chromatin

Banded Neutrophil

most common immature form seen in blood (inflammation)

• unsegmented

3 stages of a neutropil

• bone marrow

• intravascular

• tissue

Neutrophil: marrow pool

proliferation pool: early cells

maturation pool: metamyelocyte, band neutrophil

storage pool: segmented neutrophil

At what stage do neutrophils stop dividing?

maturation pool

Neutrophil: blood pool

• blood has a half life of 5-10 hours

Methods of removal of neutrophils

• spontaneous apoptosis

  • removal by macrophages in spleen, liver, bone marrow

Neutrophil: circulating neutrophil pool (CNP)

• neutrophil in blood circulation

Neutrophil: marginated neutrophil pool (MNP)

• neutrophils transiently sequestered in capillaries/post-capillary vanules/sinusoids

Neutrophils can move between

CNP and MNP

Which method is not counted in CBC?

MNP

Survival of neutrophils in tissues?

a few days

• unidirectional movement

Neutrophil migration of of blood: random contact

• step 1

• inflammatory signals originate from mononuclear cells, endothelium, fibroblasts, and other cell types

Neutrophil migration of of blood: rolling

• apart of step 1

• upregulation of adhesion and molecules

  • transient binding and release of neutrophils to endothelium (rolling;2)

Neutrophil migration of blood: Activation

additional inflammatory mediators released by neighboring wbc

• activation of neutrophils

  • increased affinity to endothelium

Neutrophil migration of of blood: Adhesion

firm bond between neutrophil and endothelial cell

Neutrophil migration of of blood: Diapedesis

• neutrophil squeezes through endothelial cell

What is the point of no return for neutrophils?

Diapedesis

• unidirectional movement

  • cannot return to circulation

Neutrophil migration of of blood: Hapatotaxis

• step 6

• neutrophil exit vessel and migrate to site of inflammation

Where do neutrophils function?

• within the tissues (not blood stream)

Increase in neutrophils does not mean?

bacterial infection

Neutrophil function

• destroys bacteria by releasing granule contents

  • oxygen dependant or independant

    • can be released into the phagosome or extracellularly

Neutrophil granules

• primary

• secondary

• tertiary

  • MYELOPEROXIDASE

MYELOPEROXIDASE

• enzyme found in primary granules

• aids in oxygen depednat (H2O2) killing of microbes

• released into phagosomes

Neutrophil extracellular traps (NET’s)

• extend processed chromatin with histones, granule proteins (cytoplasmic proteins)

  • can bind and kill bacteria, fungi, parasites, and viruses without phagocytosis

    • other cells can too

Heterophils

• equivalent to neutrophil found in exotics

• pink cytoplasmic granules

Eosinohpils

• cytoplasmic granules stain pink

  • contain condensed, segmented nucleus, similar to neutrophils

  • size and shape of granules can vary between species

Grey or vacuolated eosinophils

• variably sized (unstained granules resembling clear vacuoles)

  • dogs have no differences

  • cats w clear eosinophils have ultrastructural and cytochemical differences (but not thought to function differently)

Life of eosinophil

8-18 hours

• survives weeks to months in tissues (shorter in gastro and airways)

Function of eosinophil

• less phagocytic than neutrophils

• defense against helminths and other parasites

  • degranulation oxidative and enzymatically dependent damage

  • parasites to big for phagocytic cells

    • allergic reactions

Basophils

• cytoplasm granules stain basophilic (basic pH)

  • low numbers in health

Basophil kinetics/life span

• 6 hours

  • survive two weeks in the tissues

Basophil function

• like mast cells and eosinohpils

  • helmainth and histamine release (granules)

Mast cells

• arise from different precursors than basophils

  • can present in v low numbers in some species w systemic inflammation (cats it is uncommon and correlates w mast cell neoplasia)

Monocytes are found in

blood

Macrophages are found in

tissues

Monocytes

• variable shapes nuclei

• blue-grey cytoplasm

  • may be vacuolated or contain faint pink hue

Monocyte function

• professional phagocytes

• antigen presentation

• cytokine production

Monocytes migrate into tissues and become

• macrophages and dendritic cells

Marginating pool of monocytes where?

lungs

Monocyte marginating pool

pool of monocytes in lungs

Monocyte circulation time

2-4 days

Monocyte survival times in tissues

• unknown, long lol

M1 macrophage

• antimicrobial

  • promote inflammation

M2 macrophage

• wound repair

  • tissue remodeling, immune response

Lymphocytes

predominant leukocyte in ruminants, pigs, rodents, and other non-mammalian species

B cells

discovered in Burse of Fabricius in birds

T cells

mature in thymus

CD4+

helpter T lymphocytes

CD8+

cytotoxic T lymphocytes

NK cells

can have pink magenta cytoplasmic granules