[Reduced natural killer function in children with recurrent respiratory tract infections]. / Ridotta funzionalità natural killer in bambini con infezioni respiratorie ricorrenti.

Respiratory infections are the major cause of disease in childhood in the industrialized areas of the world. This essentially depends on two factors: immunological immaturity and immunological naivety. In most cases a virus has been considered the causative agent in respiratory infection. A defect in immune responses has been described in children with recurrent respiratory infections and in particular a decrease in CD4/CD8 T lymphocyte ratio or in IL-2 and IFN-gamma production. Our results show that Natural Killer (NK) cell activity is defective in children with recurrent respiratory infections. That is particularly noteworthy since NK cells play an important role in host defense against viral infections. At present it is difficult to understand whether the NK defect is a primary defect or it is secondary to viral infections. Further studies will help to clarify whether NK decreased activity depends on a cell damage directly caused by virus or it depends on the decreased levels of cytokines.

[Epstein-Barr virus infection. Old and new immunological aspects]. / L'infezione da virus di Epstein-Barr. Aspetti immunologici vecchi e nuovi.

EBV infection may have a wide range of clinical consequences: it is often asymptomatic; some cases-generally adolescents-develop the classic "infectious mononucleosis" syndrome; in rare cases the illness takes a severe, fatal course. EBV is also implicated in some geographic areas, in Burkitt' lymphoma and naso-pharyngeal carcinoma. Recent research has enrich our knowledge on the viral genome and the various viral antigen, but some problems are still unsolved. The "normal" immunological response to EBV infection is briefly summarized; then the abnormal immunological pattern is considered in relation to some conditions such as age, congenital and acquired immunodeficiencies and unusual clinical syndromes. Recently a group of not well defined, persistent illnesses (fever, fatigue, headache etc.) has been correlate to a "chronic" EBV infection. It becomes more and more evident that different clinical manifestations of EBV infection are always connected with a particular immunological response; between the "normal" cases and those with well defined immunodeficiency probably large group exists in which minor immunological abnormalities are responsible for a partial derepression of the virus.