How Cytolin® Was Discovered
Just over a decade ago, three scientists who were working independently of each other discovered why HIV does not cause disease in the other mammals it can infect. There are, of course, other viruses that are similar to HIV and that can cause AIDS-like diseases in animals, such as simian immunodeficiency virus (SIV) and feline immunodeficiency virus (FIV). However, the human immunodeficiency virus (HIV) only causes disease in humans and not in the other mammals it can infect, such as chimpanzees. In discovering why this is the case, researchers also demonstrated why humans infected with HIV lose virtually all of their CD4+ T cells resulting in the development of  AIDS, even though only a minority of those cells become infected with HIV. This was demonstrated by Joyce Zarling[1] then at Oncogen (now Bristol-Myers Squibb), Leonard Adelman[2] then at the University of Southern California, and Allen D. Allen[3-4] then at Olive View-UCLA Medical Center. The seminal paper, published in the Journal of Immunology in 1990, 144, 2992, was by Zarling, et al. She and her colleagues conducted a truly elegant cross-species study. It proved to a scientific certainty that the reason only humans develop AIDS in response to HIV infection is that only humans respond to the infection with a proliferation of cytotoxic T lymphocytes (CTL) that indiscriminately kill human CD4+ T cells, including healthy, uninfected CD4+ T cells.

The question that Zarling and Adelman did not answer is why this should be the case. In terms of understanding the mechanisms involved in HIV disease, one should ask what particular mechanism the anti-self, anti-CD4 CTL use to indiscriminately destroy human CD4+ T cells. Because of the huge volume of HIV-literature that was focused on many diverse issues, the key was to know where to look. As a consequence, Allen was able to ascertain the cytotoxic mechanism because he had a model to start with.

Hepatitis, when associated with hepatitis B and C virus, has been known for years to be a disease that is triggered by an infection and that results in the destruction of the liver by CTL.[5-6] The destruction of the liver occurs because its surface becomes coated with intercellular adhesion molecules (ICAM). The co-receptor to ICAM is LFA-1. What makes a CD8+ T cell a cytotoxic cell rather than a suppressor cell is the overproduction of LFA-1.[7] When the CTL circulate through the liver, the LFA-1 binds to the ICAM killing the hepatocytes or liver cells. Interferon-alpha is the gold standard for treating serum hepatitis because it down-regulates the ICAM molecules on the liver so that the CTL do not harm that organ.[8] Not surprisingly, then, Bofill, et al[9] have shown that increased numbers of CTL predict the decline of CD4 T cells in HIV patients. By knowing the mechanism of action, Allen[10] was able to identify a class of monoclonal antibodies that could prevent the indiscriminate destruction of CD4+ T cells by CTL. Cytolin® is one such antibody.

Click vial to learn the genesis of the brand name Cytolin®.