The issue of animal-rights extremism, last discussed in a Nature Immunology editorial in April 2004 (http://www.nature.com/ni/journal/v5/n4/full/ni0404-345.html), has been addressed by new government legislation. Measures passed by the UK Home Office in July 2004 and the US Congress in late 2006 classify as a criminal offense the use of force, violence and harassment against people and institutions engaging in animal testing. Unfortunately, these measures have apparently done little to dissuade fringe animal-rights activists groups, as recent events show an escalation in the severity of their attacks.

In June 2006, a Molotov cocktail–style firebomb was left at the home of Lynn Fairbanks, a primate researcher at the University of California, Los Angeles (UCLA). One year later, an explosive device was found under the car of Arthur Rosenbaum, another UCLA primate researcher. Fortunately, both incendiary devices were defective. In October 2007, the home of their colleague Edythe London was flooded with a garden hose, and in February 2008, masked people suspected but not confirmed to be involved with animal-rights groups entered the home of and physically attacked a family member of an animal researcher at the University of California, Santa Cruz. Farther afield, in 2008, the Biomedical Research Institute of Hasselt University in Belgium was burned down and the offices of Novartis in Barcelona were vandalized.

Claiming credit for many of these attacks are organizations such as Animal Liberation Front (ALF) and Animal Liberation Brigade (ALB). Distinct from organizations such as People for the Ethical Treatment of Animals and the Humane Society, which use only legal, nonviolent methods to promote their cause, ALF engages in, as the organization puts it, “direct action against animal abuse in the form of rescuing animals and causing financial loss to exploiters” and acknowledges that their actions may be illegal. Although they describe their efforts as nonviolent and promise to “take precautions not to harm any animal (human or otherwise),” their recent use of incendiary devices, flooding and, potentially, physical attacks suggests that this is not the case. ALF and ALB efforts are aided by organizations such as the UCLA Primate Freedom project, which has used the Freedom of Information Act to obtain and publish the names, photographs and home addresses of researcher 'targets' on its website, which also offers defamatory downloadable flyers for posting in the neighborhoods of these scientists.

The consequences of these attacks, in addition to the obvious personal distress, are manifold. In August 2006, UCLA researcher Dario Ringach, fearing for the safety of his family because of demonstrations outside his home and because of phone and email harassment, decided to cease primate research. The repeated targeting of the UK Huntingdon Life Sciences contract animal testing firm and many pharmaceutical companies has prompted some to move their animal testing operations to China, where they adhere to US animal testing standards but are free, at least for now, from the threats of radical animal-rights groups.

In response to the escalation in animal-rights extremism, and bolstered by increasingly stringent legislative and law enforcement efforts, academics are taking a stand. In February 2008, UCLA successfully sought a restraining order to protect against harassment by animal-rights groups. The university is also providing private security on campus and at the homes of threatened faculty members and is no longer releasing detailed information about biomedical primate research. Also in February 2008, the Society for Neuroscience released a document entitled “Best Practices for Protecting Researchers and Research: Recommendations for Universities and Institutions” that provides guidelines for universities and institutions aiming to proactively protect and to stave off attacks on staff and students. In response to extreme animal-rights tactics that resulted in halted construction on biomedical animal research facilities at Oxford University and Cambridge University, the group 'Pro-Test' was founded in Oxford, UK, in 2006. Thus far, this academic-run group has held two rallies, organized public meetings, and conducted polls finding that 94% of Oxford students support construction of the Oxford biomedical animal research facility, which recommenced in late 2004.

Perhaps not understood by extremist organizations is the fact that the creation of suitable alternatives to animal testing would be welcomed by many academics, most of whom are frustrated with the enormous financial and administrative burdens associated with animal research. As stated in original European Union Council Directive 86/609, designed to protect animals used for experimental purposes, “experiments must only take place if there is no alternative method that does not entail the use of animals”; similar statements are found in the UK Animal (Scientific Procedures) Act and the US Animal Welfare Act.

Encouragingly, efforts to devise alternative methods are underway, as indicated by the February 2008 announcement of a program in which the US Environmental Protection Agency, National Toxicology Program and National Institutes of Health will join forces to develop and test new in vitro methods for evaluating chemical toxicity. However, efforts by the UK-based group Animal Defenders International to revise European Union directive 86/609 to establish a timetable for complete replacement of primates in biomedical experiments might be premature.

Although data on responses generated in animals, even primates, are not always predictive of responses in humans, many past immunological advances (e.g., infectious properties of disease-causing agents and biological principles underlying transplant rejection) depended heavily on experiments with live animals. The development of drugs to prevent and treat such conditions also relied strongly on animal research. As in the past, for the foreseeable future and until technological advances provide suitable alternatives, animal research remains essential to biomedical research into understanding and combating human disease.