Disclosed are means, compounds, and compositions of matter useful for stimulation of natural killer cell activity. On one embodiment a composition termed QuadraMune™ comprised of pterostilbene, Nigella sativa extract, green tea extract, and broccoli. In some embodiments the invention teaches the administration of a therapeutic combination of ingredients comprising of metformin, pterostilbene, Nigella sativa, sulforaphane, and epigallocatechin-3-gallate (EGCG) to a mammal in need of natural killer cell immune modulation. In another embodiment, the invention teaches administration of said therapeutic combination to a mammal infected with said SARS-CoV-2. In some embodiments dosage of said therapeutic combination is based on inflammatory and/or immunological parameters observed in patients with COVID-19.