SKIN FERMENTS

That a definite change in the reactivity of the skin takes place during the transition from infancy to childhood has been repeatedly noted. Rolly (5), working with a variety of bacterial toxins, found that infants did not react, but that reactions occurred with advancing age. Similarly Tenner (6), using Witte's peptone, colon bacilli, and tuberculin observed that at about the period that the skin of children became increasingly sensitive to tuberculin, a corresponding reactivity was manifest toward the other antigens. It seems possible to us that this phenomenon is related to the alteration in the ferments of the skin that takes place during the transition period. Thus while the protease of the adult type of skin causes a definite autolysis, that of the fetal skin does not, the synthetic potential evidently predominating. Of greater significance seems to be the fact that the skin of the young animal contains peptidase to a considerable amount, while the adult skin seems to be without this ferment activity. If we assume that the disintegration of the native protein of the antigen is essential in eliciting certain skin tests, it would seem probable that the splitting would be less apt to take place in the young skin in which the lytic effects of the ferments are relatively suppressed. On the other hand, the young skin, containing peptidase, would be able to digest rapidly any antigen consisting of partially hydrolyzed proteins—as tuberculin—and in this way detoxicate and remove the noxious material. From these considerations the undoubted alteration of the skin reactivity taking place after infancy seems definitely correlated with changes in the proteolytic ferments. In how far they enter into and alter the specific reactions cannot be determined from the limited data so far available. Of the other ferments, the lipases, as pointed out by Porter, are possibly of importance in the resistance of the skin to tuberculous infection. It will be observed from the table that the activity of these skin ferments is less manifest in their action as esterases, on ethyl butyrate, than on the neutral fats used, oleic oil and butter fat, in this way differing from the activity of the serum. The relative resistance of the skin to tuberculous infection can, however, hardly be due to the activity of the lipase alone, for it must be kept in mind that the lepra bacillus, also rich in lipoids, is enabled to proliferate well within the epithelial tissues.