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Microbiology, 2021

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20.5 • Fluorescent Antibody Techniques 847<br />

CHECK YOUR UNDERSTANDING<br />

• In fluorescence activated cell sorting, what characteristic of the target cells allows them to be separated?<br />

Table 20.5 compares the mechanisms of the fluorescent antibody techniques discussed in this section.<br />

Fluorescent Antibody Techniques<br />

Type of<br />

Assay<br />

Mechanism<br />

Examples<br />

Direct<br />

fluorescent<br />

antibody<br />

(DFA)<br />

Uses fluorogen-antibody conjugates to label bacteria<br />

from patient samples<br />

Visualizing Legionella<br />

pneumophila from a throat swab<br />

Indirect<br />

fluorescent<br />

antibody<br />

(IFA)<br />

Detects disease-specific antibodies in patent serum<br />

Diagnosing syphilis; detecting<br />

antinuclear antibodies (ANA) for<br />

lupus and other autoimmune<br />

diseases<br />

Flow<br />

cytometry<br />

Labels cell membranes with fluorogen-antibody<br />

conjugate markers excited by a laser; machine<br />

counts the cell and records the relative fluorescence<br />

Counting the number of<br />

fluorescently labeled CD4 or CD8<br />

cells in a sample<br />

Fluorescence<br />

activated cell<br />

sorter (FACS)<br />

Form of flow cytometry that both counts cells and<br />

physically separates them into pools of high and low<br />

fluorescence cells<br />

Sorting cancer cells<br />

Table 20.5

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