Occasionally, the non-toxic hemagglutinin of Abrus precatorius (Q9M6E9; AAG) is also included as the fifth protein under the collective name 'abrin'.

Abrin-a is formed after the cleavage of a signal peptide sequence and post-translational modifications such as glycosylation and disulfide bridge formation in the endoplasmic reticulum (ER).

In terms of structure, abrin-a is related to the lectin, ricin, produced in the seeds of Ricinus communis.

The rosary pea is common to tropical regions, and is occasionally employed as an herbal remedy for certain conditions.

[10] The severity of the effects of abrin poisoning vary on the means of exposure to the substance (whether inhaled, ingested, or injected).

[11] In clinical studies involving cancer patients, up to 0.3 μg/kg of intravenous abrin immunotoxin was tolerated without the development of serious symptoms of toxicity.

Due to its biochemical properties and its similarity to ricin, it is believed that abrin is at least partially degraded in the gastrointestinal tract.

[7] Murine studies show that there is an accumulation of abrin after injection, in the liver, kidneys, spleen, blood cells, lungs, and heart.

[15] The major symptoms of abrin poisoning depend on the route of exposure and the dose received, though many organs may be affected in severe cases.

[6] The later signs and symptoms of exposure are caused by abrin's cytotoxic effects, killing cells in the kidney, liver, adrenal glands, and central nervous system.

[6] Within a few hours of inhaling abrin, common symptoms include fever, cough, airway irritation, chest tightness, pulmonary edema (excess fluid accumulated in the lungs), and nausea.

Their blood pressure may drop dramatically, keeping oxygen from reaching the brain and other vital organs in a condition called shock, and respiratory failure may occur, which can be fatal within 36 to 72 hours.

This ultimately results in multi-system organ failure, hypovolemic shock, vascular collapse, and death.

Abrin in the powder or mist form can cause redness and pain in the eyes (i.e. conjunctivitis) in small doses.

Higher doses can cause tissue damage, severe bleeding at the back of the eye (retinal hemorrhage), and vision impairment or blindness.

Abrin exposure can be prevented when it is present in large quantities by wearing appropriate personal protective equipment.

Oxygen therapy, airway management, assisted ventilation, monitoring, IV fluid administration, and electrolyte replacement are also important components of treatment.