Immune system helps to fight infections
Tanel Tenson introduces the complicated molecular-biological background of immunity of multicellular organisms. Multicellular organisms fight against infections with the help of a complex immune system. The article attempts to review the basic molecular mechanisms that determine the effectiveness of immune system. Components of both adaptive and innate immunity are described. The article is complemented with numerous colorful illustrations and a short “dictionary” of terms used in immunology.

From animal vaccines to AIDS-vaccins
Lauri Peil describes the history of vaccinology and its fast development at present. Vaccination as such was first used in 1796, when English doctor Edward Jenner infected 13-year old boy James Phipps with cowpox virus, which does no harm to humans, but results in life-long immunity to smallpox. New discovery was made. Next vaccines were introduced more than 80 years later, by Louis Pasteur and others, along with the term ‘vaccine’ to describe Jenner's accomplishment. At present time, vaccines against 26 different infections are used and more are being actively developed. Vaccines can be divided into different classes, depending on how they are produced and on their mode of action. These classes are: killed, inactivated microbes as vaccines, live, attenuated microbes as vaccines, purified microbial component vaccines, recombinant vaccines and DNA vaccines. Of those, attenuated and recombinant vaccines are the ones used mostly at present time, although killed microbes also have some use. Despite of elegant idea and design, no DNA vaccines are yet commercially available, although many of them are in clinical trials. In future, new vaccines against more than 20 diseases are expected, including AIDS, tuberculosis and cancer, to name a few. It's clear that vaccination can't prevent and cure every disease but it has proved to be a very useful tool in nowadays medicine.

Evolution of the immune system
Sirje Tiimusk looks at the development of animals’ immune system. All multicellular organisms have an innate (non-specific) immune system against viruses, bacteria, fungi and parasites. The innate immune system represents an ancient host defense system and is based on the recognition of molecular structures exclusively found in microorganisms. These innate mechanisms have been conserved in the evolution and follows similar pathways in vertebrates and some invertebrates. The adaptive (specific) immunity arose relatively recently in the evolution of animals, probably after the separation of the main line of jawed vertebrates from that of hagfish and lampreys. The adaptive immunity is based in specific antigen receptors (Ig and TCR) expressed by specialized cells (lymphocytes) that are present in all jawed vertebrates. This specific immune system acts in the context of the conserved innate immune system, which has important regulatory function.

Half a century of tracking autoimmunity
Raivo Uibo gives an overview of the discovery of autoimmunity as a phenomenon, as well as of new research trends. While the common knowledge of autoimmunity is usually limited to vaccines, there is much more to the science of autoimmunity. Moreover, many accepted principles that have dominated for decades have proven to be wrong.

Essay
Ann Marvet disputes about the charm and power of board-trail.

European rarities in Estonia
Kai Vellak features three especially rare moss species: Busbaumia viridis, Dichelyma capillaceum and Dicranum viride. All three species grow only in old-growth forests with decaying tree trunks.

Interview:
Toomas Kukk has interviewed Erkki Truve, professor of gene technology.

Autoimmune diseases: familiar become unfamiliar
Pärt Peterson looks at reasons why sometimes the autoimmune system sometimes works against itself and explains the mechanisms behind it. The main function of immune system is to protect an organism from the pathogens, viruses, bacteria and parasites of the outer world. Because of those positive features we usually think of immune reaction as something positive. However, in some cases the immune system can turn against the person as an enemy.

The holy plant of Native Americans improves the immune system
Pharmacist Ain Raal stresses the strengths and weaknesses of Echinacea purpurea, a fashionable medicinal plant of present time. It is known as the strengthener of immune system and for its antiseptic effect.

Eesti Loodus enquires
Tõnu Möls considers the present and future of the Estonian Naturalists’ Society– the society that celebrates its 150th anniversary.
Tiit Kändler gives a short overview of the activities of the NGO “Loodusajakiri” (Nature Journal) during the two years of its existence.

Yeasts make cider
Urmas Kokassaar looks at mechanisms behind making cider – a popular weak alcoholic beverage, which is made by fermenting fruit juices with yeasts.

Karst creates beautiful features on the Balkan coast
Vallo Tilgar recommends Croatia as a travel destination. Although the territory of the country is small, one can experience several natural wonders, such as lakes of Plitvice, the waterfalls of Krka River and the canyons and walls of Paklenica.

Practical tips: the colorful and many-faced Genus of maples
Ivar Sibul writes about domestic and introduced species of maples, giving a good overview of the origin and appearance of each, supplementing the description with comparative photos.

In European Union no batteries go to a trashcan
Peeter Eek explains the essence of hazardous wastes, their disposal possibilities in Estonia and the future in the conditions of European Union. Unlike in other countries, the majority of hazardous wastes in Estonia are made up by oil shale production wastes.