Senescence-accelerated mice (SAMP1/TA-1) treated repeatedly with lipopolysaccharide develop a condition that resembles hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis is a life-threatening systemic hyperinflammatory disorder with primary and secondary forms. Primary hemophagocytic lymphohistiocytosis is associated with inherited defects in various genes that affect the immunological cytolytic pathway. Secondary hemophagocytic lymphohistiocytosis is not inherited, but complicates various medical conditions including infections, autoinflammatory/autoimmune diseases, and malignancies. When senescence-accelerated mice (SAMP1/TA-1) with latent deterioration of immunological function and senescence-resistant control mice (SAMR1) were treated repeatedly with lipopolysaccharide, SAMP1/TA-1 mice displayed the clinicopathological features of hemophagocytic lymphohistiocytosis such as hepatosplenomegaly, pancytopenia, hypofibrinogenemia, hyperferritinemia, and hemophagocytosis. SAMR1 mice showed no features of hemophagocytic lymphohistiocytosis. Lipopolysaccharide induced upregulation of proinflammatory cytokines such as interleukin-1β, interleukin-6, tumor necrosis factor-α, and interferon-γ, and interferon-γ-inducible chemokines such as c-x-c motif chemokine ligands 9 and 10 in the liver and spleen in both SAMP1/TA-1 and SAMR1 mice. However, upregulation of proinflammatory cytokines and interferon-γ-inducible chemokines in the liver persisted for longer in SAMP1/TA-1 mice than in SAMR1 mice. In addition, the magnitude of upregulation of interferon-γ in the liver and spleen after lipopolysaccharide treatment was greater in SAMP1/TA-1 mice than in SAMR1 mice. Furthermore, lipopolysaccharide treatment led to a prolonged increase in the proportion of peritoneal M1 macrophages and simultaneously to a decrease in the proportion of M2 macrophages in SAMP1/TA-1 mice compared with SAMR1 mice. Lipopolysaccharide appeared to induce a hyperinflammatory reaction and prolonged inflammation in SAMP1/TA-1 mice, resulting in features of secondary hemophagocytic lymphohistiocytosis. Thus, SAMP1/TA-1 mice represent a useful mouse model to investigate the pathogenesis of bacterial infection-associated secondary hemophagocytic lymphohistiocytosis.