Ccvi. the Immunological Reaction to the Enzyme Papain

REPORTS have been highly contradictory with respect to the possible development of increased anti-enzymic activity in the serum of a subject which has received repeated injections of a given enzyme preparation. Wells [1925], in reviewing the subject, considers the general thesis very much open to doubt. Probably the most definite evidence of a positive nature is the work by Kirk and Sumner [1931; 1932] with crystallised urease preparations. This particular enzyme is much more stable in the presence of serum than most enzymes and such a property would seem to be a requisite for the production of an antienzyme. Northrop [1930], for instance, failing to obtain anti-enzymic effects with a crystallised pepsin preparation, attributed the failure to the recognised instability of pepsin in blood-serum. The vegetable enzyme, papain, by virtue of its relative stability in serum [Walton, 1931, 1, 2] is of special interest in this regard. In the previous studies [Ehrenreich, 1900; Stenitzer, 1908; Achalme, 1901; Pozerski, 1909] concerning the possible development of an antipapain effect proteolytic assay methods have been used which were evidently of slight sensitiveness. For instance, the presence of fluctuating amounts of serumproteases in the same animal was not recognised in such studies. Ehrenreich [1900] and Achalme [1901] were unable to obtain antipapain effects with rabbits and guinea-pigs, while Stenitzer [1908] reported an anti-enzymic effect in one case with a goat. On the basis of these considerations, the problem was reinvestigated, as reported here, using a method of proteolytic assay which is unusually accurate at relatively high dilutions. The sensitiveness of this particular method was such that the development of a relatively slight antipapain effect should have manifested itself in the recorded measurements.