In Situ Infiltration of Natural Killer‐Like Cells Induced by Intradermal Injection of the Nucleic Acid Fraction from BCG

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Abstract
Intradermal injection of MY‐1, a nucleic acid fraction extracted from Mycobacterium bovis strain BCG, induced in situ infiltration of mononuclear cells, most of which were asialo GM1 (GA1)‐positive as determined by immunofluorescence microscopy. The infiltration occurred with as little as 1 μg of MY‐1 and lasted for a week. Double immunofluorescence microscopy revealed that the infiltrating GA1‐positive cells were all positive for Ly‐5, and partially positive for Thy‐1.2, but negative for Mac‐1, Ia, μ‐chain, Lyt‐1, Lyt‐2, L3T4, and Fc receptor II. They contained neither peroxidase nor nonspecific esterase. The infiltrating cells thus markedly resembled natural killer (NK) cells in their cytochemical characteristics and surface markers. DNase and RNase destroyed the GA1‐positive cell‐inducing activity of MY‐1. These results indicate that the nucleic acid components of MY‐1 are responsible for this effect.