[Physiological and pathological aspects of the immune reactions (author's transl)]

The basic principles of modern immunology are reviewed. In analogy to the nervous defence mechanism of the body the immune reactions are divided into a "specific" afferent, "unspecific" efferent and central regulatory part. The old conception of the "lock and key" relation between antigen and antibody is re-interpreted in terms of molecular chemistry. The dual aspects of the immune response is interpreted as part of an over-all network within which the humoral and cellular defence systems are organized to act in concert. Allergy is considered to be solely a special type of immune reaction; while its disease-producing effects are undisputed its physiological significance is still obscure. The immune mechanism involved in specific densitization is discussed in detail.