C57BL/6

C57BL/6, often referred to as "C57 black 6" or just "black 6" is a common inbred strain of lab mouse. It is probably the most widely used "genetic background" for genetically modifed mice for use as models of human disease. They are the most widely used lab mouse strain, due to the availability of congenic strains, easy breeding, robustness, and their relationship to GM models, making them ideal controls.

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Appearance and behavior

  Dark brown, nearly black, coat. Easily irritable temperament. They have a tendency to bite, and cannot be handled like a typical pet mouse or even more docile laboratory strains such as BALB/c.

C57BL/6 mice which are group-housed also display barbering behavior, in which the dominant mouse in a cage selectively removes hair from its subordinate cage mates. Mice that have been barbered have large bald patches on their bodies, commonly around the head, snout, and shoulders, although barbering may appear anywhere on the body. Both hair and vibrissae may be removed. Barbering is more frequently seen in female mice; male mice are more likely to display dominance through fighting.^[1]

C57BL/6 as a "Th1 responder"

C57BL/6 has certain immunophenotypes that distinguish it from other inbred strains like BALB/c. For example the immunological response to the same pathogen in C57BL/6 mice is often of an opposite spectrum compared to BALBb/c mice, namely C57BL/6 shows Th1 and BALB/c shows Th2 response in response to intracellular pathogen Leishmania major, where a Th1 response results in a resistant ie healer phenotype (since the pathogen is intracellular), whereas a Th2 response results in a susceptible (nonhealer) phenotype.

Though this trait had been observed in these two strains since 1988, in an article published in 2000 by Mills et al.^[2] these observations were systematized and generalized to other strains of mice. Even without biasing towards Th1 or Th2 by priming through infection, the strains differ in their macrophages' ability to be activated, as measured from their arginine metabolic programs when stimulated by Interferon gamma or LPS or both:

• M-1 macrophages from typical Th1 responders: C57BL/6 or B10.D2 mice, preferentially produce NO by action of iNOS
• M-2 macrophages from typical Th2 responders: DBA or BALB/c mice, preferentially produce ornithine and urea by action of arginase.

Response to diseases

Plasmodium (malaria)

• P. yoelii YM = lethal
• P. yoelii 17XL = lethal
• P. yoelii 17XNL = "non-lethal" (though up to 50% mortality is not unusual)
• P. berghii = lethal (with cerebral malaria)
• P. vinkii = lethal
• P. chabaudi AS = non-lethal

References