These immunotoxins have worked very well for in vitro applications, e.g. bone marrow transplants . Although they have not worked very well in many in vivo situations, progress in this area of research shows promise for the future. In bone marrow transplant procedures, RTA-immunotoxins have been used successfully to destroy T lymphocytes in bone marrow taken from histocompatible donors . When expressed intracellularly, the toxigene product causes cell death. The introduction and expression of a toxigene in transgenic animals or plants may lead to cell type-specific ablation , which can be used to study developmental cell lineages or to generate animal models of degenerative diseases.
Neuroscientists can selectively destroy neurons by injecting ricin into nerves.
Retrograde axonal transport mechanisms bring the toxin to the neuronal cell bodies where the ribosomes are localized. Ultrastructural analysis reveals that ricin first causes the dispersion of polyribosomes, and then the rough endoplasmic reticulum disorganizes into smooth vesicles. When suicide transport is observed after injection of the toxin, it confirms the presence of N-acetyl galactosamine residues on the neuronal cell surface. Strategies in suicide transport work very well in studies of adult peripheral sensory and motor neurons because they are sensitive to ricin. Neurons in the central nervous system of adults are resistant to ablation by ricin, whereas young developing brains are sensitive, suggesting that brain development involves changes in glycosylation of CNS neurons.