Critically, however, not all probiotics confer benefit—Bifidobacterium combined with PD-L1 blockade eradicated melanoma in mice (258), whereas commercial probiotics (Bifidobacterium longum or L. rhamnosus GG-based) accelerated tumor progression by diminishing IFNγ+CD8+ T cell infiltration (259), highlighting the danger of “one-size-fits-all” approaches and the need for strain-tumor matching. The gene discussed is CD8A; the disease is melanoma.