A Review of Current Theories regarding Immunity (Concluded)

Extract

Two questions. In concluding our review of this division of the subject, which deals with the parts played by the bodily presence of cellular protoplasm as contrasted with the activity of the chemical products of that protoplasm, which from their solubility may act at a distance from the cell producing them, there are two points which may be alluded to. Firstly, it is difficult to see how, granted that two substances are necessary for bactericidal action, these substances can in the first instance at least meet the bacterium except within a cell. Unless all immune bodies are represented in the serum by go-betweens (Zwischenkörper),—by bodies of an identical nature and differing only in that they are subservient to the normal metabolism of the body—how, when a bacterium gains entrance to the blood, does it come in contact with the immune body for which its protoplasm has the affinity? The receptor, which fixes the group in the bacterium corresponding with it, is within a cell,—how can the affinities be satisfied until the bacterium gets within the cell? It is not till the cell has been robbed of the use of these receptors and they become over-regenerated that the immune body becomes free and can be found in the serum. It is possible that all immune bodies are represented by go-betweens, and that a certain amount of the latter must be kept free in the serum for ordinary metabolism, and it is also possible that when the gradient—to use a physical phrase—between the cell and the blood plasma becomes great so far as the amount of go-betweens present in the latter is concerned that the cell becomes more active and secretes more of the material which is being more rapidly taken up than is usual in ordinary metabolism. Thus while the extra-cellular destruction of bacteria is easy to understand in the later steps of immunisation there is a difficulty about the earlier stages.