User:Ghusoon Abdulrasool

Neutrophil function tests:

These are group of laboratory tests that assess various aspects of neutrophil's function that are used to diagnose neutrophil's related disorders. The most common is chronic granulamatous disease.

Introduction:
Neutrophils are professional phagocytic cells with a crucial function in the defense against bacteria and fungi. Granulocyte defects comprise two major categories: quantitative and qualitative defects.The latter related to neutrophil's function.Primary neutrophil dysfunction significant enough to cause clinical disease accounts for < 6% of all primary immune deficiency however, there are many clinical situations which lead to secondary neutrophil dysfunction

Laboratory tests of neutrophil function:
A- Sample Requirements:

Blood should be collected at a slow rate with a large bore needle directly into the anticoagulant and the blood should be investigated as soon as possible after collection, because neutrophils rapidly undergo spontaneous apoptosis.

Storage and transport: blood should be collected in EDTA or citrate in a polypropylene tube and kept at room temperature to maintain a low level of metabolic activity and to avoid adhesion of the neutrophils to the container. Keeping the blood samples at a constant temperature is essential as it prevents non specific neutrophils activation.Avoid Heparin as it can activate the complement system and generate complement fragment C5a in the plasma resulting in cell activation Plastic tubes should be used for processing samples.

B-Specific tests:

1-Chemotaxis:

Ability to locomote upon a chemoattractant gradient.This can be tested using Boyden diffusion chamber: This instrument consists of a lower chamber in which a chemotactic agent is placed and upper chamber (in which the cells are brought). These chambers are Separated by a filter with pores of 5–8 mm. Through diffusion of the chemotactic agent, a concentration gradient of these molecules builds up in the pores of the filter.The cells in the upper compartment react to this gradient by moving into the pores.This chemotactic response can be measured in two ways.

A-Using stop filter’’ with pores of only 0.45 mm placed underneath the first filter  Counting the number of cells collected either microscopically or by measuring the radioactivity of prelabeled cells

B-The assay can be stopped before the cells have traversed the complete length distance travelled by the fastest cells (the ‘‘leading front’’). can be measured microscopically.

2-Phagocytosis:

Using microorganisms or particles.Classically: neutrophils are incubated with labelled microorganisms, samples are taken and washed or treated with an enzyme to remove non-ingested microbes, and the cell-associated label is measured. Modern techniques employ flowcytometry: with the advantages of accuracy and speed.

References:
1- Assessment of neutrophil function - II. Laboratory tests of neutrophil function. Postgraduate Medical Journal (1986) 62, 1089-1092

2- Manual of Molecular and clinical laboratory immunology. 7th edition.