Facts about infection, inflammation, immunology, and microbiology

These four subjects are closely connected. Infections are caused by microorganisms, the immune system protects us against infections and immune responses also cause inflammation, which is involved in combatting infection, but can, if stimulated in other ways, cause chronic inflammatory conditions.



Bacteria are found everywhere around us. Some bacteria promote human health while others cause a variety of infectious diseases.

Cellular and molecular research into the interactions of bacteria and human beings occupies the boundaries between bacteriology, cell biology and immunology. When combined, this can result in new discoveries that lead to treatments for bacterial infections, for example, respiratory infections, tuberculosis, urinary tract infections and infections in the intestines and the skin.


Viruses are small microbes that carry only basic genetic information. They require enzymes and proteins from the host’s cells in order to reproduce. Viruses can cause acute and chronic diseases such as HIV, tuberculosis, meningitis and influenza. They can also trigger tumours in humans and animals.  

The challenge of virology research is to identify viruses and their disease potential, as well as to develop tools for chemical and immunological treatments. Their relatively small genome makes them ideal candidates for the analysis of how illnesses and tumours arise when the viral genome is associated with, or integrated into, the human genome.


Parasites are disease causing eukaryotes, organisms that have cells with nuclei. They are divided into ectoparasites (for example flies, lice and ticks) and endoparasites, which live inside the host organism. The latter group includes protozoa, which are a group of single-celled organisms, as well as worms from various phyla.

A large part of parasite research at KI is directed toward malaria, but also other parasitic diseases from other regions of the world are being studied. The genetic differences between parasites are enormous, and studying these can lead not only to new biological discoveries, but also an improvement in human health around the globe.


Immunology is concerned with how the body defends itself against infectious agents, for example, bacteria, parasites and viruses. The body’s immune response is based primarily on the reaction of immune cells; lymphocytes react to the infectious agent by producing antibodies, and killer cells destroy the infectious agent. They also learn to recognise the infectious agent so that they react more strongly to any subsequent infection. One of the goals of immunological research is to strengthen the body’s defences against infectious agents, for example by vaccination.

After transplantation the immune response is activated and the body tries to reject the transplanted tissue. In this case, it is desirable to be able to decrease the strength of the immune response. In other cases, the immune response is directed against the body’s own tissues and generates a, so-called, autoimmune response, which frequently results in the start of a chronic inflammatory condition. 

Molecular Immunology Research

There is a strong tradition of molecular immunology at Karolinska Institutet. The development of new immunological therapies requires a detailed understanding of basic cell biology. This is also important for the identification of patients in the early stages of immunological and inflammatory illnesses and for following their progress during treatment. Furthermore, if immunological and inflammatory processes are increasingly characterised at the molecular level, this can lead to a redefinition of diseases, as different mechanisms can lead to similar diseases and because apparently unrelated diseases can actually have a similar cause.  


Inflammation develops in a tissue as the result of damage or a stimulus, normally resulting from external factors. A large number of cells are involved in the inflammatory response, above all the white blood cells called macrophages, mast cells and lymphocytes. Acute inflammation usually heals quickly. 

Many common illnesses have their origin in a chronic inflammatory condition, for example rheumatoid arthritis (RA), skin diseases such as some types of eczema and psoriasis, some intestinal diseases, muscle diseases and even arteriosclerosis and myocardial infarction.  The underlying causes of these diseases are not clearly understood; genetic factors are involved together with poorly understood external causes, resulting in disease.

Immunomodulatory Treatment

Immunomodulatory treatment is one of the cornerstones of modern drug therapy, incorporating everything from salicylic acid and steroids, to cytostatics and immunosuppressants. During the last decade, specific new drugs in the form of antibodies, soluble receptors and recombinant proteins have made advances in the treatment of chronic inflammatory diseases, including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), allergy and psoriasis. Karolinska Institutet, thanks to its strong patient-based research into inflammation and autoimmunity, is an international leader in the advancement of knowledge that forms the basis of these new principles of therapy.

Immunotherapy and Transplantation

Immunotherapy and transplantation are two other rapidly developing fields in which research at Karolinska Institutet is leading the way. Immunotherapy involves giving antigens, immune cells or immunologically active proteins to patients, with the aim of strengthening or redirecting the immune defence. Transplantation of stem cells or organs is a growing field in clinical medicine, in which the functioning of the immune defence is the key to the clinical outcome. Detailed knowledge of immunological reactions to foreign tissue is needed to understand how rejection reactions can be prevented and how the immune system can benefit the patient in stem cell transplantation.