Lepromin Testing with Diluted Antigen

It is now a well-recognized fact that, imperfect as 'modern treatment of leprosy may be, the results of it are making it more and more difficult in most places to obtain bacillus-rich lepromas suitable for makinglepromin. And at the same time more and more stress is being laid on the use of the Mitsuda test, for which that antigen is required. Thus has arisen a new and unprecedented problem. One way of partially relieving the situation is to improve the technique of preparing lepromin and lessen the wastage involved in the classical Mitsuda-Hayashi technique. Thus the WHO Expert Committee incorporated in its reportI an otherwise unpublished method by which the yield of lepromin of normal concentration can be materially increased. A lot of 1,300 cc. prepared by that method was recently supplied to the South Pacific Commission, and it is reported as giving satisfactory and even superior results. 2 Another approach, initiated by Floch, is to use high dilutions of lepromin.3 It has been known practically from the first that wide variations of bacillus concentration may occur without vitiating the results, and Hayashi himself once referred to the reaction as of "all or nothing" type. Some of the preparations described in the early days, when attempts were being made to standardize the antigen by bacillus counts, varied tremen-