phytohaemagglutinin

As a toxin, it can cause poisoning in monogastric animals, such as humans, through the consumption of raw or improperly prepared legumes, e.g., beans. Measured in haemagglutinating units (hau), a raw red kidney bean may contain up to 70,000 hau, but this is reduced to between 200 and 400 hau when properly cooked.{{cite web|title=Bad Bug Book (2012)|work=Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Phytohaemagglutinin|url=https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|archive-url=https://web.archive.org/web/20130418013247/http://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|url-status=dead|archive-date=April 18, 2013|publisher=Food and Drug Administration|access-date=2 February 2022|year=2012|quote=Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau}} Studies by British scientists recommend soaking beans for at least five hours, discarding the water, and then boiling the beans in fresh water at {{convert|100|C}} for at least thirty minutes.{{cite web|title=Bad Bug Book (2012)|work=Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Phytohaemagglutinin|url=https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|archive-url=https://web.archive.org/web/20130418013247/http://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|url-status=dead|archive-date=April 18, 2013|publisher=Food and Drug Administration|access-date=2 February 2022|year=2012|quote=Studies done by British scientists suggest that beans should be soaked in water for at least 5 hours,the water poured away, and the beans boiled in fresh water for at least 30 minutes}} A pressure cooker at 15 psi may be used to cook beans in 45 minutes without presoaking. {{Cite journal |doi = 10.1111/j.1365-2621.1983.tb14831.x|title = Effect of Heat Processing on Hemagglutinin Activity in Red Kidney Beans|year = 1983|last1 = Thompson|first1 = Lilian U.|last2 = Rea|first2 = Ramona L.|last3 = Jenkins|first3 = David J. A.|journal = Journal of Food Science|volume = 48|pages = 235–236}} Insufficient cooking, such as in a slow cooker at 75 °C/ 167 °F, may not completely destroy the toxins.{{cite web|url=https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|archive-url=https://web.archive.org/web/20130418013247/http://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|url-status=dead|archive-date=April 18, 2013|title=Bad Bug Book: Handbook of Foodborne Pathogenic Microorganisms and Natural Toxins. 2nd ed.|year=2012|website=US Food and Drug Administration (FDA)|publisher=US Food and Drug Administration|access-date=3 February 2019}}

Beans also contain alpha amylase inhibitor, but not in sufficient quantities to affect the digestion of starch after consumption of beans.{{cite journal | vauthors = Layer P, Carlson GL, DiMagno EP | title = Partially purified white bean amylase inhibitor reduces starch digestion in vitro and inactivates intraduodenal amylase in humans | journal = Gastroenterology | volume = 88 | issue = 6 | pages = 1895–902 | date = June 1985 | pmid = 2581844 | doi = 10.1016/0016-5085(85)90016-2 }}

Poisoning can be induced from as few as four raw beans. Symptoms usually begin with extreme nausea and vomiting within one to three hours of ingestion, followed by diarrhea. Abdominal pain has been reported in some people. Recovery is usually spontaneous and rapid, occurring within three to four hours after onset of symptoms, although some cases have required hospitalization.{{cite web|title=Bad Bug Book (2012)|work=Foodborne Pathogenic Microorganisms and Natural Toxins Handbook: Phytohaemagglutinin|url=https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|archive-url=https://web.archive.org/web/20130418013247/http://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf|url-status=dead|archive-date=April 18, 2013|publisher=Food and Drug Administration|access-date=2 February 2022|year=2012}}

In medicine these proteins are useful and are used as a mitogen to trigger T-lymphocyte cell division and to activate latent HIV-1 from human peripheral lymphocytes. Lymphocytes cultured with phytohaemagglutinin can be used for karyotype analysis. Stimulation of peripheral blood lymphocytes by phytohaemagglutinin presents a classic model of transition of cells from the quiescent G₀ phase of the cell cycle into G1-, and subsequently progression through S-, G2- and M- phases of the cycle.{{cite journal | vauthors = Darzynkiewicz Z, Traganos F, Sharpless T, Melamed MR | title = Lymphocyte stimulation: a rapid multiparameter analysis | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 73 | issue = 8 | pages = 2881–4 | date = August 1976 | pmid = 822422 | doi=10.1073/pnas.73.8.2881| pmc = 430788 | bibcode = 1976PNAS...73.2881D | doi-access = free }}

PHA activates T cells by binding to sugars on glycosylated surface proteins including the T cell receptor. Binding by PHA crosslinks these proteins, causing T cell activation and the downstream NFAT pathway. HIV-1 replication is enhanced with T cell activation, hence the observed ability to activate the virus from latency.{{cite web |title=PHA-P |url=https://www.invivogen.com/phap |website=InvivoGen |date=21 February 2017}}

In neuroscience, anterograde tracing is a research method that uses the protein product phytohaemagglutinin PHA-L as a molecular tracer that can be taken up by the cell and transported across the synapse into the next cell thereby tracing the path of axonal projections and relative connections that nerve impulses travel beginning with the source located at the perikaryon (cell body or soma) and through the presynaptic part located on neuron's efferent axon all the way to the point of termination at the efferent synapse which then provides input to another neuron.{{cite book| first= Neil R.| last= Carlson | name-list-style = vanc | year= 2007| title= Physiology of Behavior, 9th ed.| pages= 144| location= Boston| publisher=Pearson Education, Inc.| isbn= 978-0-205-46724-2}}

Prior to 1960, crude extracts of PHA were known to coat the surface of red blood cells, make them heavier, and thereby improve the separation of the white cell buffy coat. Peter Nowell, an immunologist and pathologist at the University of Pennsylvania in Philadelphia, was using PHA for this purpose in 1960 when he discovered it also had the ability to stimulate mitotic division of lymphocytes from normal peripheral blood. Prior to his discovery, these cells were assumed to be the terminal end-products of differentiation. This work had tremendous implications for the constitutional study of chromosomal disorders. T. C. Hsu's 1979 book "Human and Mammalian Cytogenetics an Historical Perspective" (ISBN 978-1-4612-6159-9) is an excellent resource for this history.{{cn|date=June 2024}}

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• {{MeshName|Phytohemagglutinins}}

{{Lectins}}

Category:Proteins

Category:Lectins

Category:Foodborne illnesses

Category:Legume lectins