This paper deals with capsular reactions and soluble antigens in two species of pathogenic fungi, Torula histolytica (Cryptococcus hominis or Torulopsis neoformans) and Sporotrichum schenckii. Although capsular reactions (1) of bacteria have been utilized for some years both in practical diagnosis and in various fundamental studies, a survey of the accessible literature did not reveal any report of serological reactions on the capsules of fungi. The demonstration of capsular reactions for Torula histolytica and Sporotrichum schenckii seems of general microbiological interest because it establishes the occurrence of a fundamental immunological phenomenon in another biological group (fungi), and at the same time contributes new information on the agents of two diseases.H u m a n infections with these fungi are not of high incidence. However, Torula infections of the central nervous system have a high case mortality, and a new aspect of interest in Sporotrichum infections has been introduced b y the magnitude and the unusual epidemiology of outbreaks of over 2800 cases of sporotrichosis among mine workers in South Africa (2, 3).There is a considerable literature on both Torula histolytica and Sporotrlckum schenckii, but the immunological information is not systematic nor far advanced. The papers on Torula (4)(5)(6)(7)(8)(9)(10) give the general impression that most strains have poor immunogenic capacity, although in a few instances serum with reasonably good agglutinating titres have been gotten. Precipitation reactions, when obtained, have been only with undiluted serum; the test antigens usually were filtrates of broth cultures or various extracts of the cells. Kligman (9) prepared a product, presumably of capsular origin, but concluded that it lacked serological properties.We could find no reports of a purified polysaccharide from Torula histolytica, which was proved to be serologically reactive, and indeed there has been a rather general belief that the capsular material of this fungus probably is not serologically reactive.In the case of Sporotrichum, agglutination and complement fixation with patients' serum were reported as early as 1908 (11).

This paper deals with a comparison of the antibody-evoking capacities (in rabbits) of weakly encapsulated and of strongly encapsulated cells of Cryptococcus neoformans and with the influence of the number of the fungus cells (amount of vaccine) upon the strength and the promptness of the antibody response. The data on these two points contribute toward a better understanding of the immunogenic properties of this fungus and, in addition, present an instance in which antibodies reactive with the large capsules of strongly encapsulated forms of a species were produced more effectively by immunization with weakly encapsulated forms than by immunization with the strongly encapsulated forms of the species. The prevailing impression that Cryptococcus antiserums are difficult or inconvenient to produce has come from the fact that a number of workers failed with all strains tried, others failed with some strains although succeeding with others, and all who have reported the production of reasonably potent antiserums have employed prolonged series of injections over periods ranging from 64 to 12 weeks. The literature consists of the papers of Stoddard and Cutler

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