Читать книгу Principles of Virology, Volume 2 - Jane Flint, S. Jane Flint - Страница 61

Microbes are everywhere. They are on our hands, in our food, on the lips of those we kiss, on the ground and in the oceans, filling the air we breathe. For young children who play in dirt, scrape their knees, and pick their noses, interactions with microbes are even more frequent and diverse. As we begin a series of chapters dedicated to immune responses and viral diseases, perhaps the right question to ask is not “What makes us sick?” but rather, “How can we possibly manage to stay healthy?”

If students of immunology are asked to list components of the host response to infection, typical responses will include mention of antibodies, cytotoxic T lymphocytes, and interferons. These answers are not incorrect per se , but to focus only on attributes of the immune system misses the bigger picture: by the time a virus or other pathogen has been engulfed by a phagocyte or induced a T cell response, it has already successfully bypassed an impressive fortress of defenses. These defenses, such as skin, mucus, and stomach acid, might seem much more primitive than the elegantly coordinated innate and adaptive immune responses. Nevertheless, they block the overwhelming majority of infections.

However, such sentries and barriers are imperfect, despite millions of years of evolution in the presence of microbes. When viruses breach these barriers, infections of host cells and attendant disease can occur. The genomes of successful viruses encode proteins that modify, redirect, or block these, as well as other, defenses. For every host defense, there will be a viral offense. It is remarkable that the genome of every known virus on the planet, no matter its size, encodes countermeasures to modulate the defenses of its host. As we shall see, many of these “anti-host response” strategies (Box 2.1) are aimed at the body’s first line of protection: the physical barriers to infection.

For comments and a personal account related to the chapter topic, see the interview with Dr. Neal Nathanson: http://bit.ly/Virology_Nathanson.