Ricin: A protein phytotoxin from the seeds of Ricinus communis, the castor oil plant. It agglutinates cells, is proteolytic, and causes lethal inflammation and hemorrhage if taken internally.Abrin: A toxic lectin from the seeds of jequirity, Abrus precatorius L. Very active poison. Five different proteins have so far been isolated: Abrus agglutinin, the component responsible for: hemagglutinating activity, & abrins a-d, the toxic principals each consisting of two peptide chains are held together by disulfide bonds.Immunotoxins: Semisynthetic conjugates of various toxic molecules, including RADIOACTIVE ISOTOPES and bacterial or plant toxins, with specific immune substances such as IMMUNOGLOBULINS; MONOCLONAL ANTIBODIES; and ANTIGENS. The antitumor or antiviral immune substance carries the toxin to the tumor or infected cell where the toxin exerts its poisonous effect.Castor Bean: Common name for Ricinus communis, a species in the family EUPHORBIACEAE. It is the source of CASTOR OIL.Ricinus: A plant genus of the family EUPHORBIACEAE, order Euphorbiales, subclass Rosidae. The seed of Ricinus communis L. is the CASTOR BEAN which is the source of CASTOR OIL; RICIN; and other lectins.Plant Lectins: Protein or glycoprotein substances of plant origin that bind to sugar moieties in cell walls or membranes. Some carbohydrate-metabolizing proteins (ENZYMES) from PLANTS also bind to carbohydrates, however they are not considered lectins. Many plant lectins change the physiology of the membrane of BLOOD CELLS to cause agglutination, mitosis, or other biochemical changes. They may play a role in plant defense mechanisms.RNA, Ribosomal, 28S: Constituent of the 60S subunit of eukaryotic ribosomes. 28S rRNA is involved in the initiation of polypeptide synthesis in eukaryotes.Chemical Warfare Agents: Chemicals that are used to cause the disturbance, disease, or death of humans during WARFARE.Ribosome Inactivating Proteins, Type 1: Ribosome inactivating proteins consisting of only the toxic A subunit, which is a polypeptide of around 30 kDa.Toxins, Biological: Specific, characterizable, poisonous chemicals, often PROTEINS, with specific biological properties, including immunogenicity, produced by microbes, higher plants (PLANTS, TOXIC), or ANIMALS.Diphtheria Toxin: An ADP-ribosylating polypeptide produced by CORYNEBACTERIUM DIPHTHERIAE that causes the signs and symptoms of DIPHTHERIA. It can be broken into two unequal domains: the smaller, catalytic A domain is the lethal moiety and contains MONO(ADP-RIBOSE) TRANSFERASES which transfers ADP RIBOSE to PEPTIDE ELONGATION FACTOR 2 thereby inhibiting protein synthesis; and the larger B domain that is needed for entry into cells.