[Useful stimulation of the immune system].

'Useful stimulation of the immune system is that type of stimulation which results in an immune response (particularly in the mucosae) that will reduce possible pathological effects following exposure to pathogenic organisms and/or toxins over prolonged periods'. Stimulation of the immune system, such as follows a 'natural supply' of antigen at the side of the mucosa and the question whether, on the whole, vaccination will result in useful stimulation of the immune system, are briefly discussed against the background of this definition. A number of instances are cited to illustrate differences and similarities between 'natural' stimulation and stimulation produced by vaccination. Finally, speculations on the use of a more natural system of vaccination are engaged in, a system which utilizes the predictable presence of antigen at the side of the mucosa in conjunction with generalized stimulation of the immune system by administration of adjuvants not including antigen.