A method of inducing a Type I interferon response in a mammalian subject that presents with a microbial infection, cancerous tumor or hematological malignancy that comprises administering an amount of a halogenated xanthene as discussed above, effective to induce the Type I interferon response. A method of enhancing a mammalian immunogen-specific immune response that comprises contacting mammalian cells, in vivo or present in a mammalian cell growth supporting medium, with an adjuvant-effective amount of a halogenated xanthene, and an immunogen to which that response is to be enhanced. A mammalian HX compound-adjuvanted vaccine composition that contains an immunogen present in a vaccine-effective amount along with an adjuvant-effective amount of a halogenated xanthene (HX) compound and one or more excipients present at about 0.001% by weight to 10% by weight of the vaccine composition dissolved or dispersed in a pharmaceutically acceptable diluent.