Rough-Form Lipopolysaccharide Increases Apoptosis in Human CD4 + and CD8 + T Lymphocytes

Abstract

Immunosuppression induced by lymphocyte apoptosis is considered an important factor in the pathogenesis of sepsis and has been demonstrated in both animal models of lipopolysaccharide (LPS)-induced endotoxemia and septic patients. As rough-form LPS (R-LPS) has recently been shown to elicit a stronger immunological response than regular smooth-form LPS (S-LPS), we aimed to assess the apoptosis-inducing capabilities of R-LPS in different subsets of lymphocytes (CD4 + T cells, CD8 + T cell, B cells and NK cells). Using multicolour flow cytometry on human peripheral blood mononuclear cells, we found that R-LPS increased apoptosis in CD4 + and CD8 + T cells assessed by annexin V and propidium iodide (AV +PI -), compared with both S-LPS-stimulated and unstimulated cells. 7-Amino-actinomycin D and staining for intracellular active caspase-3, which are considered later signs of apoptosis, did not reveal the same results. Both forms appeared to inhibit apoptosis in B cells, but no LPS-form-specific effect was seen on B or NK cells. Our results indicate that R-LPS induces a stronger AV +PI --assessed apoptotic response in T cells than S-LPS. Our findings emphasize the importance of T cell apoptosis in endotoxemia and advocates for control of LPS form in both endotoxemia research and clinical trials with Gram-negative infections. © 2011 The Authors. Scandinavian Journal of Immunology © 2011 Blackwell Publishing Ltd.