[Active immunization against tick-borne encephalitis in the elderly]

30 healthy young persons and 19 healthy aged people (between 60-75 years) were vaccinated against tick-borne meningoencephalitis virus. The antibody production of the young people was compared to that of the aged ones following vaccination. It has been found that the antibody production of the aged people was delayed, and more elderly people than young ones showed an increase of the IgM-bearing lymphocytes after vaccination. The morphological changes of the circulating lymphocytes were identified with electron microscope. The presence of cytoplasmic inclusions called parallel tubular arrays could be observed in the course of immunization. The inclusions were not found before vaccination, and it is suggested that the inclusions are related to the in-vivo antigen stimulation.