Equis ISSN 2398-2977

Skin: phytohemagglutinin test - T-lymphocyte function

Contributor(s): Prof Derek Knottenbelt

Overview

  • The test should be performed at, or at least, within 4 days of birth in foals suspected of having poor immunity.
  • The test can equally be performed in older horses - the value and implications of the test to the owner are less easily accepted at a later stage.

Sampling

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Tests

Methodologies

  • Aseptic preparation of a clipped area of skin on the side of the neck.
  • Measurement of skin thickness using accurate tuberculin testing or fat thickness calipers/slide.
  • Injection: 50 microg PHA in 0.05 ml phosphate buffered saline intradermally using 1 ml tuberculin/insulin syringe and a 25 g x 1 cm needle.
  • Using the same technique inject the same volume of phosphate buffered saline at adjacent site - this acts as a negative control.
  • Measure skin thickness at two sites after 24 h - some swelling is usually present in normal foals after 4 h.

Technique (intrinsic) limitations

  • An in vitrotest is not subject to the variations of an in vivosystem and both methods have advantages and disadvantages.

Result Data

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Further Reading


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