CD8A and neoplasm: L. johnsonii in particular has been reported to reduce proinflammatory responses in murine liver,32 restore normal levels of CD4+ and CD8+ T cells in spleen,33 and trigger differentiation of splenic CD4+ T cells into tumoricidal Th17 cells in cyclophosphamide treated tumor mice.34 Given that we have also found viable L. johnsonii residing in cells and tissues systemically it is tempting to speculate that gut symbionts, such as L. johnsonii, could also function as endosymbionts in order to exert their immunomodulatory effects.