The ICR mouse, formally named CD-1, is a widely utilized general-purpose laboratory animal. Because of its predictable and well-documented characteristics, researchers across many disciplines rely on this mouse. This broad application makes understanding its background, traits, and uses relevant for anyone interested in how biomedical research is conducted.
The ICR Name and Its Origins
The name “ICR” is an acronym for the Institute of Cancer Research, where the stock was first established. The lineage of these mice traces back to non-inbred albino mice from Switzerland, imported to the United States in 1926 by the Rockefeller Institute. Their descendants were subsequently distributed, leading to the establishment of the Ha/ICR stock in 1948 at the Institute of Cancer Research in Philadelphia. This specific colony gave rise to the ICR designation. From there, the mice were shared with commercial breeders like Charles River Laboratories in 1959, which helped standardize and popularize their use.
Key Characteristics of ICR Mice
A defining feature of ICR mice is that they are an outbred stock, meaning they are genetically heterogeneous. This genetic variation is intentionally maintained and can be advantageous for studies aiming to mimic the varied genetic makeup of the human population. Their docile temperament also makes them easy to handle in a laboratory setting. Physically, ICR mice are recognized by their albino coat, with adult males weighing between 30 and 40 grams, while females are slightly smaller. They are also known for their general hardiness and strong reproductive performance, characterized by large litter sizes, which ensures a steady supply for research.
Applications in Scientific Discovery
The combination of hardiness, availability, and genetic diversity makes the ICR mouse a versatile model in many areas of research. They are used in toxicology and safety testing to assess the effects of new chemicals, environmental agents, and pharmaceutical drugs. The variability within the outbred stock can provide insight into how a genetically diverse population might respond to a substance. In pharmacology, these mice are employed to study drug efficacy and mechanisms of action. Their use extends to immunology, vaccine development, and infectious disease studies, where their robust immune response is a valuable trait.
Choosing ICR Mice for Research
Researchers select ICR mice for practical reasons, with cost-effectiveness and widespread availability being primary advantages. Their excellent reproductive performance ensures that large numbers of animals can be produced quickly and affordably. The general robustness of the stock also means fewer animals are lost during studies due to unrelated health complications.
However, the primary characteristic to consider is their outbred nature. While the genetic variability is useful for modeling population-level responses, it can be a limitation. This heterogeneity often means that larger sample sizes are required to achieve statistically significant results compared to studies using inbred strains. The decision to use ICR mice depends on whether the research question benefits from genetic diversity or requires the precision of a genetically identical background.