Allergie respiratoire et virus

Viral respiratory tract infections are a major cause of wheezing in infants. Investigators determined that 80% to 85% of school-aged children with wheezing episodes were tested positive for virus. To more fully understand how viral respiratory tract infections influence asthma, investigators have evaluated the effect of respiratory tract injections on airway symptoms, function, and inflammation. Although the mechanisms by which respiratory viruses enhance lower airway inflammation are not established, cytokines may play a key role in this process. The respiratory epithelial cell is a principal host for respiratory virus replication und is likely to be the first source of cytokines during an acute infection. T cells orchestrate immune responses to both allergens and viruses, and regulate effector cells with virucidal and proinflammalory effects. Although studies demonstrate that virus-specific T cells may contribute to virus-induced lung disease, evidence to define the role of virus-specific T lymphocytes in asthma has not been fully established. Some injections early in life may also have an important immunoregular role in the subsequent development of allergy and asthma. Atopy is characterised by exaggerated Th-2 cell responses to commun allergens with secretion of cytokines such as IL-4 and IL-5 that promote IgE production and eosinophil activation. In contrast, childhood injections typically induce a Th-1 cell response, characterised by secretion oj interferon-γ which enhances the antiviral activities of effector cells. These two types of T cell responses are mutually antagonistic.