Skin eosinophilia from influenza viruses. An experimental histological study

The authors would first like to stress the increasing frequency of bronchial asthma during or after influenza. To find an explanation for this occurrence they observed tissue reactions following an injection of viral material. In their experiments, they injected into the skin of guinea pigs, strains of the Hong Kong, Texas and USSR influenza viruses using current vaccines, sacrificing groups of animals 2, 6, 24, 48 hours and 7 days after the injection. The histological study revealed the following picture of reaction to influenza viruses. Two hours after the injection: marked and diffuse infiltration of eosinophils in the connective tissue of the skin. After 6 hours: the infiltration shows a predominance of neutrophils. After 24 hours: the neutrophil infiltration is predominant and diffuse. There is evidence of considerable degranulation of eosinophils. The cutaneous histiocytes undergo fibrocytic and marcophagic proliferation. After 28 hours, the same picture. After 7 days there is sever degeneration with a peripheral fibroblastic reaction. The most important finding of this experiment is the early marked infiltration of eosinophils which follows the injection of the influenza viruses. The eosinophil infiltration appears to be related to the release of histamine caused by influenza viruses. The histological examination did not reveal the presence of immune allergic-type cells at any time. Therefore, the onset of asthmatic attacks would appear to be more related to the histamine-releasing action of the influenza viruses rather than to their sensitizing activity. Naturally, the latter may occur in human pathologies.