In a series of papers Youmans and Youmans (1–8) have reported that ribosomal or ribonucleic acid (myc. RNA)2 preparations obtained from living cells of the attenuated H37Ra strain of Mycobacterium tuberculosis were as immunogenic in CF-1 mice as viable cells of the H37Ra strain. This comparison was based upon the amount of RNA present in each vaccine. The immunity engendered by these preparations is specific and long lasting.

The RNA preparations also have certain nonspecific activities of particular interest. For example, this material can act as a potent adjuvant for the production of antibody to bovine γ globulin (BGG) in mice, being as active in this respect as complexes of poly-adenylic and poly-uridylic acids (poly A:U) (9). In addition, the myc. RNA can serve as an effective adjuvant for the induction of experimental allergic encephalomyelitis in guinea pigs (10).

Insofar as immunogenic activity against tuberculous infection is concerned, apparently the myc.

1

This investigation was supported by Public Health Service Research Grant AI-01636 from the National Institute of Allergy and Infectious Diseases and a grant from the Canal Zone Tuberculosis Association.

2

Abbreviations used in this paper: BGG, bovine γ globulin; poly A:U, poly-adenylic and poly-uridylic acids; FIA, Freund's incomplete adjuvant; myc RNA, ribosomal or ribonucleic acid preparations from M. tuberculosis.

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