Interleukin-10 functions in vitro and in vivo to inhibit bacterial DNA-induced secretion of interleukin-12.

Bacterial DNA (bDNA) has a number of biologic properties, including the ability to induce interleukin-12 (IL-12) production by macrophages. We studied the role of the regulatory cytokine IL-10 as a potential inhibitor of bDNA-induced IL-12 production. IL-10 concentrations as low as 0.

Bacterial DNA-induced NK cell IFN-gamma production is dependent on macrophage secretion of IL-12.

Bacterial DNA (bDNA) activates B cells and macrophages and can augment inflammatory responses by inducing release of proinflammatory cytokines. We found that bDNA stimulation of mouse spleen cells induced NK cell IFN-gamma production that was dependent upon the presence of unmethylated CpG motifs, and oligonucleotides with internal CpG motifs could also induce splenocytes to secrete IFN-gamma. The bDNA-induced IFN-gamma response was strictly macrophages dependent.

Bacterial DNA induces NK cells to produce IFN-gamma in vivo and increases the toxicity of lipopolysaccharides.

Microbial products released during bacterial infection induce cytokine-mediated inflammatory responses that can be protective, but excessive release of inflammatory cytokines may promote development of the sepsis syndrome. We examined the ability of bacterial DNA to induce in vivo cytokine release and to potentiate the toxicity of LPS. Intravenous treatment of mice with Escherichia coli (EC) DNA, but not calf thymus (CT) DNA, induced a rapid (within 4 h) dose-dependent increase in serum IFN-gamma and splenic IFN-gamma-forming cells.

IFN-gamma promotes IL-6 and IgM secretion in response to CpG motifs in bacterial DNA and oligodeoxynucleotides.

Lymphocyte recognition of characteristic structural features in microbial DNA may contribute to immune defense by promoting protective immune responses. The dinucleotide CpG is significantly under-represented in vertebrate DNA and is usually methylated. In contrast, CpG dinucleotides are generally present at the expected frequency in bacterial DNA and are unmethylated.

Regulation of differentiation of peritoneal B-1a (CD5+) B cells. Activated peritoneal macrophages release prostaglandin E2, which inhibits IgM secretion by peritoneal B-1a cells.

The B-1a (CD5+) subset of B cells comprises the majority of B cells in the peritoneal cavity and is implicated in the pathogenesis of certain autoimmune diseases and lymphoproliferative disorders. When we stimulated purified B-1a cells with LPS, they produced more than four times as much IgM as similarly stimulated whole peritoneal cells (containing the same number of B-1a cells). Reconstitution experiments using FACS-purified peritoneal cell populations revealed that resident peritoneal macrophages (Mac1+, B220-) profoundly inhibited the LPS response of peritoneal B-1a cells.

T cell-independent and T cell-dependent B cell activation increases IFN-gamma R expression and renders B cells sensitive to IFN-gamma-mediated inhibition.

We have studied the relationship between B cell activation and the ability of IFN-gamma to inhibit B cell differentiation. The LPS activation of conventional and CD5+ B cells resulted in increased IFN-gamma R expression and increased the ability of IFN-gamma to inhibit LPS-induced B cell differentiation correlated with increased IFN-gamma R expression. We detected increased B cell IFN-gamma R expression 12 h after activation, and maximal IFN-gamma R expression was observed at 24 h.

Interferon-gamma regulation of B lymphocyte differentiation: activation of B cells is a prerequisite for IFN-gamma-mediated inhibition of B cell differentiation.

The Th1 and NK cell-derived cytokine interferon-gamma (IFN-gamma) influences both immune and inflammatory responses, and under some circumstances, IFN-gamma can inhibit B cell differentiation. We found that IFN-gamma inhibited LPS-induced IgM production in B cells by reducing the precursor frequency of IgM-secreting cells. This occurred without a significant decrease in B cell proliferation in response to either LPS or F(ab')2 anti-IgM.

Effect of anti-CD4 on CD4 subsets. I. Anti-CD4 preferentially deletes resting, naive CD4 cells and spares activated CD4 cells.

Anti-CD4 has been extensively studied in murine models of autoimmunity and transplantation. The timing of anti-CD4 administration in these systems is critical because anti-CD4 effectively blocks primary T-dependent responses but does not diminish ongoing or memory responses in immunized animals. These differential effects suggest that anti-CD4 suppresses a subpopulation of CD4+ cells.

Regulation of differentiation in CD5+ and conventional B cells. Sensitivity to LPS-induced differentiation and interferon-gamma-mediated inhibition of differentiation.

We have analyzed the response of conventional and CD5+ B cells to the opposing signals delivered by LPS and interferon-gamma (IFN-gamma). Cultured CD5+ B cells secrete more IgM than conventional B cells in response to low concentrations of LPS. This increase in LPS-induced IgM production is due to an increased precursor frequency of IgM-secreting cells in CD5+ B cells.

Activation events in hapten-specific B cells from tolerant mice.

We have studied hapten-binding cells from the spleens of normal and tolerant adult mice in terms of their ability to enlarge, proliferate, and differentiate into antibody-secreting cells. Tolerant B cells showed clear defects in intermediate activation events in addition to a deficit in antibody-secreting cells. In these studies, isolated B cells were stimulated by T cell independent Ag with lymphokines, or with mitogens, in the absence of filler cells.

Differential expression of a surface antigen recognized by a monoclonal antibody, J11d, on unprimed and primed B cells.

Functional studies of both polyclonal and antigen-specific responses have suggested that murine B cells differ in the expression of an antigen recognized by a rat anti-mouse monoclonal antibody, called J11d. Using both positive and negative selection, we now demonstrate that the J11d marker is differentially displayed on B lymphocytes responding to LPS vs anti-mu, as well as on unprimed vs specific antigen-primed B cells. Thus, cytotoxic elimination of cells expressing high levels of J11d (J11d-hi) reduced LPS-driven B cell proliferation by 60 to 80% but had no effect on anti-mu stimulated B cell growth.

Mechanism of sodium independent calcium efflux from rat liver mitochondria.

On the basis of primarily two types of observations, it has been suggested that the Na+-independent Ca2+ efflux mechanism of rat liver mitochondria is a passive Ca2+-2H+ exchanger. First, when a pulse of acid is added to a suspension of mitochondria loaded with Ca2+, a pulse of intramitochondrial Ca2+ is often released, even in the presence of the inhibitor of mitochondrial Ca2+ influx, ruthenium red. Second, at a pH near 7, the stoichiometry of Ca2+ released to H+ taken up by Ca2+-loaded mitochondria, following treatment with ruthenium red, has been observed to be 1:2.