Disruption of T cell tolerance to self-immunoglobulin causes polyclonal B cell stimulation followed by inactivation of responding autoreactive T cells

Macrophage-Instructed Intracellular Staphylococcus aureus Killing by Targeting Photodynamic Dimers

The survival of Staphylococcus aureus inside phagocytes is considered to be the sticking point of long-term chronic inflammation. Here, we fabricate peptide-chlorophyll-based photodynamic therapy (PDT) agents with "sandwich" dimeric structure to enhance the PDT effect and active targeting property to eliminate intracellular infections, which could be seen as prospective antibacterial agents for inflammation.

T cells specific to hapten carrier but not to carrier alone assist in the production of anti-hapten and anti-carrier antibodies

We examined the immune response of Balb/c mice to antigens prepared by conjugating 2-phenyloxazolone (phOx) to a foreign protein, ovalbumin (OVA), or a self-protein, mouse serum albumin (MSA), in order to study how these chemical modifications would affect immune recognition. We found that anti-OVA antibodies and CD4(+) T cells produced by OVA immunization reacted with OVA as well as with phOx-OVA. Anti-phOx antibodies were produced by phOx-OVA immunization and, interestingly, T cells from these mice reacted only with phOx-OVA but not with the intact OVA. These results suggested that the classical model of hapten-carrier immunization, in which B cells specific to hapten are activated with assistance from T cells specific to a carrier protein, might not be a major route for production of anti-hapten antibodies in hapten-carrier immunization. Furthermore, phOx-MSA immunization induced production of anti-phOx antibodies, which could not be accounted for in terms of the assistance of carrier-specific T cells because of the absence of MSA-specific T cells. Therefore, we proposed a new model in which anti-hapten B cells are assisted by T cells specific to the haptenated carrier.

Induction of antigen-specific cytotoxic T lymphocytes by immunization with negatively charged soluble antigen through scavenger receptor-mediated delivery

Antigen-specific cytotoxic T lymphocytes (CTL) are essential for the immunotherapy against cancer or infection diseases although, conventionally, immunization with antigens in soluble form cannot induce CTL. In the present study, we have demonstrated for the first time that ovalbumin (OVA)-specific CTL can be induced without any adjuvants by immunization with soluble OVA with negative charges through scavenger-mediated delivery of antigens to antigen presenting cells (APC). Succinylated, maleylated and aconitylated derivatives were synthesized to allow the introduction of negative charges. All these derivatives can induce OVA-specific CTL and, especially, the CTL activity of mice immunized with maleylated derivatives was comparable with that with OVA emulsified with CFA, known to be the strongest adjuvant. Efficient antigen-specific T cell proliferation and IFN-gamma production were also observed for the OVA derivatives. The OVA derivatives also showed significant protective effects on the growth of OVA-expressing E.G7 tumor cells. In conclusion, the present study demonstrates that the introduction of negative charges to soluble antigens will be a useful strategy for the development of vaccines.

T cell proliferative responses to malondialdehyde-acetaldehyde haptenated protein are scavenger receptor mediated

Malondialdehyde-acetaldehyde (MAA) haptenated proteins have been described in disease processes related to prolonged oxidative stress (via malondialdehyde production), such as alcohol liver disease (ALD), non-alcoholic non-steatohepatitis (NASH) and atherosclerosis. Experimentally, high titer IgG1 antibody responses are seen after immunization without adjuvant; however, T cell proliferative responses and the role of scavenger receptors in this immunogenicity has not previously been described. In this study, T cell proliferative responses to the carrier protein, but not the MAA hapten itself, were identified in vitro. Moreover, these T proliferative responses were inhibited when MAA-hen egg lysozyme (HEL) was co-immunized with excess scavenger receptor ligand polyG (poly-guanylic acid), implicating the role of (a) scavenger receptor(s) in initiating the T helper cell response. Activated B cells were unable to process and present MAA-HEL preferentially to T cells, while thioglycollate-elicited (but not Con A-elicited) macrophages and dendritic cells (DC) did so with approximately 32-fold less MAA-HEL than native antigen necessary to initiate equal proliferative responses. While this preferential processing and presentation may be related to several factors, preferential binding of MAA haptenated proteins mediated by scavenger receptors may be one mechanism. IL-4 was absent from the supernatants of T proliferative assays despite a strong IgG1 response in vivo, although the TH2 cytokines IL-6 and IL-10 were expressed. Since the modification of proteins by the MAA have previously been shown to occur after ethanol consumption in vivo, the ability of MAA haptens to experimentally enhance immune responses, specifically humoral and T cell responses, may represent mechanisms by which autoimmune phenomena found in ALD occur.

Intracellular delivery of drugs to macrophages

Toxic side effects which often complicate successful therapy in a number of diseases possibly arise due to the fact that at therapeutically effective concentrations the non-target cells in the body are also exposed to the cytotoxic effects of the drugs. Minimization of such adverse reactions might be feasible through drug delivery modalities that would reduce the uptake of the drugs by non-target cells and selectively deliver the drug only to the target cells (and/or intracellular sites) at relatively low extracellular concentrations. The current generic approach to site-specific drug delivery consists of attaching the therapeutic agent to a carrier recognized only by the cells where the pharmacological action is desired. Two types of recognition elements on the surface of target cells are being exploited for this purpose, viz., (i) antigens capable of generating specific, non-cross reactive antibodies, and (ii) receptors on the cell surface capable of efficient transport of the ligands. In general, incomplete specificity for the target cells and poor internalization of antibody-drug conjugates still limit the usefulness of antibodies for site-specific drug delivery applications necessitating exploration of alternatives. The alternate possibility is to exploit the exquisite cell type specificity and high efficiency of endocytosis of macromolecules mediated by specific receptors present on the surface of target cells for delivering drugs. A large number of infectious, metabolic, and neoplastic diseases are associated with macrophages leading to morbidities and mortalities to millions of people worldwide, thus an appropriate design of a drug delivery system to macrophages will be of tremendous help.

Hypergammaglobulinemia and autoantibody induction mechanisms in viral infections

Polyclonal hypergammaglobulinemia is a characteristic of chronic inflammatory conditions, including persisting viral infections and autoimmune diseases. Here we have studied hypergammaglobulinemia in mice infected with lymphocytic choriomeningitis virus (LCMV), which induces nonspecific immunoglobulins as a result of switching natural IgM specificities to IgG. The process is dependent on help from CD4+ T cells that specifically recognize LCMV peptides presented by B cells on major histocompatibility complex class II molecules. Thus, hypergammaglobulinemia may arise when specific helper T cells recognize B cells that have processed viral antigens irrespective of the B cell receptor specificity. This nonspecific B cell activation may contribute to antibody-mediated autoimmunity.