Ly6C(+) monocyte efferocytosis and cross-presentation of cell-associated antigens.

Recently it was shown that circulating Ly6C(+) monocytes traffic from tissue to the draining lymph nodes (LNs) with minimal alteration in their overall phenotype. Furthermore, in the steady state, Ly6C(+) monocytes are as abundant as classical dendritic cells (DCs) within the draining LNs, and even more abundant during inflammation. However, little is known about the functional roles of constitutively trafficking Ly6C(+) monocytes. In this study we investigated whether Ly6C(+) monocytes can efferocytose (acquire dying cells) and cross-present cell-associated antigen, a functional property particularly attributed to Batf3(+) DCs. We demonstrated that Ly6C(+) monocytes intrinsically efferocytose and cross-present cell-associated antigen to CD8(+) T cells. In addition, efferocytosis was enhanced upon direct activation of the Ly6C(+) monocytes through its corresponding TLRs, TLR4 and TLR7. However, only ligation of TLR7, and not TLR4, enhanced cross-presentation by Ly6C(+) monocytes. Overall, this study outlines two functional roles, among others, that Ly6C(+) monocytes have during an adaptive immune response.

CD103-CD11b+ dendritic cells regulate the sensitivity of CD4 T-cell responses to bacterial flagellin.

Toll-like receptor 5 (TLR5) has been widely studied in an inflammatory context, but the effect of TLR5 on the adaptive response to bacterial flagellin has received considerably less attention. Here, we demonstrate that TLR5 expression by dendritic cells (DCs) allows a 1,000-fold enhancement of T-cell sensitivity to flagellin, and this enhancement did not require the expression of NLRC4 or Myd88. The effect of TLR5 on CD4 T-cell sensitivity was independent of the adjuvant effect of flagellin and TLR5 ligation did not alter the sensitivity of ovalbumin (OVA)-specific T cells to OVA. In the spleen, the exquisite T-cell sensitivity to flagellin was regulated by CD4-CD8α- DCs and was blocked by a monoclonal antibody to TLR5. In the mesenteric lymph nodes, flagellin-specific T-cell activation was regulated by a population of CD103-CD11b+ DCs. Thus, TLR5 expression by mucosal and systemic DC subsets controls the sensitivity of the adaptive immune response to flagellated pathogens.

Comparison of γδ T cell responses and farnesyl diphosphate synthase inhibition in tumor cells pretreated with zoledronic acid.

Exposing human tumor cells to nitrogen-containing bisphosphonates, such as zoledronic acid (Zol), greatly increases their susceptibility to killing by γδ T cells. Based on this finding and other studies, cancer immunotherapy using γδ T cells and nitrogen-containing bisphosphonates has been studied in pilot clinical trials and has shown benefits. Although Zol treatment can render a wide variety of human tumor cells susceptible to γδ T cell killing, there has not been a systematic investigation to determine which types of tumor cells are the most susceptible to γδ T cell-mediated cytotoxicity. In this study, we determined the Zol concentrations required to stimulate half maximal tumor necrosis factor-α production by γδ T cells cultured with various tumor cell lines pretreated with Zol and compared these concentrations with those required for half maximal inhibition of farnesyl diphosphate synthase (FPPS) in the same tumor cell lines. The inhibition of tumor cell growth by Zol was also assessed. We found that FPPS inhibition strongly correlated with γδ T cell activation, confirming that the mechanism underlying γδ T cell activation by Zol is isopentenyl diphosphate (IPP) accumulation due to FPPS blockade. In addition, we showed that γδ T-cell receptor-mediated signaling correlated with γδ T cell tumor necrosis factor-α production and cytotoxicity. Some lymphoma, myeloid leukemia, and mammary carcinoma cell lines were relatively resistant to Zol treatment, suggesting that assessing tumor sensitivity to Zol may help select those patients most likely to benefit from immunotherapy with γδ T cells.

Identification and characterization of molten globule-like state of hen egg-white lysozyme in presence of salts under alkaline conditions.

In the present study, we elucidated the effect of potassium salts on alkali denatured hen egg white lysozyme (EC 3.2.1.17) using intrinsic/extrinsic fluorescence as well circular dichroism (CD) spectroscopic methods. Intrinsic fluorescence studies revealed that various potassium salts mediate stabilization of lysozyme against alkali denaturation. Far and near UV CD spectrum studies, showed that 2M KCl induced appreciable amount of secondary structure with minimum tertiary contacts in lysozyme at pH 12.6. Acrylamide quenching studies suggest that at pH 12.6, the presence of 2M KCl causes reduced accessibility of the quencher to tryptophan residues of the protein presumably because of its compact conformation. In summary, the results of present study suggest that lysozyme attains a compact folded intermediate with molten globule like characteristics at alkaline pH in presence of potassium chloride.

Sperm membrane lipid liposomes can evoke an effective immune response against encapsulated antigen in BALB/c mice.

In an earlier study, we provided strong evidence that liposomes made of sperm membrane lipids (spermatosomes) can deliver entrapped molecules to the cytosol of target cells. Now we have evaluated the immunological behavior of spermatosome-encapsulated soluble antigen ovalbumin (OVA) in BALB/c mice. Spermatosome-mediated antigen delivery can affect both cytosolic and endosomal antigen-processing pathways, simultaneously, leading to the generation of CD4+ T-helper and CD8+ cytotoxic T-cell responses. Isotype studies revealed that immunization with spermatosome-encapsulated OVA elicits mainly IgG2a and IgG1 subclasses of antibodies. A potential vaccine candidate should impart long-lasting protection against infection; to this end, immunization with spermatosome-encapsulated OVA resulted in expression of CD44 and CD62L cell-surface markers on T cells, suggestive of a desirable memory response. We conclude that spermatosome encapsulation is a useful strategy for vaccine production, because it enhances the immunological activity of the encapsulated antigen.