Dean D. Manning

Immunity to blood-stage murine malarial parasites is MHC class II dependent

To determine whether MHC class II antigen presentation is essential for the induction of protective immunity against blood-stage malarial parasites, we used gene-targeted knockout (KO) mice to follow the time-course of nonlethal Plasmodium yoelii and Plasmodium chabaudi infections in two models of MHC class II deficiency. Infection of MHC class II KO (A(-/-)) mice with either parasite species resulted in an unremitting hyperparasitemia, whereas MHC-intact control mice resolved their parasitemia. In contrast, invariant chain KO (Ii(-/-)) mice, which present antigen via recycled but not nascent MHC class II molecules, eventually cured their infections when infected with P. yoelii. P. chabaudi parasitemia declined to subpatent levels in most Ii(-/-) mice but then recrudesced. Immunity to blood-stage malaria may be achieved by cell-mediated and antibody-mediated mechanisms of immunity, as such, the findings in A(-/-) mice indicate an essential role for MHC class II presentation of malarial antigens. Moreover, they suggest that protective immune responses to malarial antigens capable of eliminating blood-stage parasites are T cell dependent and can be induced with antigens processed in early and late endosomes.

The effects of interleukin-15 on human γδ T cell responses to Plasmodium falciparum in vitro

We observed that the gammadelta T cell subset expands when human peripheral blood mononuclear cells (PBMC) from malaria-naive donors are cultured with Plasmodium falciparum lysate in the presence of IL-2 or IL-15, cytokines that utilize two common IL-2 receptor subunits. IL-15 induced the expansion of the gammadelta T cell subset at all levels tested, whereas IL-2 was not stimulatory at high levels. Flow cytometric analysis of apoptosis using the TUNEL assay indicated that the percentage and absolute number of gammadelta T cells undergoing apoptosis were greater in cultures stimulated with antigen and IL-2 than in cultures stimulated with either antigen and IL-15 or control erythrocyte lysate and IL-2. The ability of IL-15 to enhance gammadelta T cell function was also assessed; the results suggest that IL-15 can function with IL-2 to enhance the capacity of gammadelta T cells to inhibit parasite replication. Together these data indicate that IL-2 and IL-15, which both bind to IL-2Rbeta and IL-2R(gamma)c, enhance gammadelta T cell function, but they appear to have different effects on proliferation and survival.

Inability of Intravenously Injected Monocellular Suspensions of Human Bone Marrow to Establish in the Nude Mouse

Mononuclear suspensions of normal and leukemic human bone marrow cells were injected into lethally irradiated nude mice. As judged by splenic focus assay, cells of human bone marrow suspensions were uniformly unable to establish colonies in the spleen, although comparably treated bone marrow cells from genetically unrealted mice readily produced such colonies. It thus appears that the nude mouse is able to prevent establishment of intravenously injected human bone marrow cells by means not involving T cell-dependent immunologic discrimination.

Pathogenicity of Campylobacter jejuni in intraperitoneally or intravenously inoculated ferrets.

Ferret kits inoculated intravenously (IV) withCampylobacter jejuni after pretreatment with parenteral iron developed more severe systemic signs and more prolonged bacteremia than untreated inoculated controls. Watery diarrhea began in both groups 2–16 h after inoculation and lasted less than 48 h.C. jejuni was cultured from rectal swabs 2–8 h after inoculation, and gut colonization persisted up to 15 days, suggesting that colonization does not necessarily induce diarrhea. Gut colonization occurred as rapidly after IV inoculation of ferrets in which the common bile duct had been ligated as it did in unligated controls.C. jejuni apparently reached the intestinal lumen by mucosal invasion from the bloodstream. Bacteremia following natural infection could thus result in repeated passages ofC. jejuni across the gut wall, exposing the mucosa to both the bacterial cells and their metabolic products. Histological evidence of an inflammatory response in the mucosa, without severe epithelial damage, suggests a toxin-mediated secretory diarrhea.

Fc dependence of anti-μ antibody-induced isotype suppression of mice☆

The mechanisms by which heterologous anti-μ antibodies suppress humoral immunity in BALB/c mice were investigated. IgG and (Fab′)2γ fragments were prepared from goat antimurine μ antiserum and normal serum. Groups of animals were injected intraperitioneally thrice weekly from birth through 28 days of life with one of these preparations. Immunization of these mice with sheep red blood cells was performed on Days 18 and 25, and all mice were assessed for antibody production, immunoglobulin levels, and residual anti-μ activity on Day 30. Animals treated with the whole IgG anti-μ preparation had no IgM (direct) and essentially no IgG (indirect) anti-sheep red blood cell antibody-producing splenocytes, no serum IgM, very low serum lgG2 levels, and free circulating residual anti-μ activity. In contrast, these immunologic parameters from F(ab′)2 anti-μ-treated mice were similar to those in animals receiving normal goat IgG or F(ab′)2 fragments. Moreover, despite conclusive demonstration of the persistence of functional F(ab′)2 anti-μ fragments in circulation of injected mice during the critical 7-day postnatal period in which suppression is induced, anti-μ activity could not be found in the F(ab′)2 group on Day 30. These results indicate that F(ab′)2 anti-μ-treated mice were immunocompetent and further suggest (i) that isotype suppression in BALB/c mice by anti-μ antibody is Fc dependent and (ii) that simultaneous binding to cell surface IgM and the Fc receptor on the B cell by intact IgG anti-μ antibody may constitute the inhibitory signal.

In vivo immune stimulation of mice by anti-μ antibodies: Generation of high serum levels of a low molecular weight IgM product

Abstract These studies show that anti-μ antibodies first injected into BALB/c mice as young adults exhibit a marked in vivo stimulatory effect, manifested by the appearance in circulation of large quantities of an aberrant IgM product. This stimulatory property extends to both rabbit and goat anti-μ antisera which have been raised against either myeloma or normal IgM but is not demonstrable for normal sera or antisera against γ or α heavy chains. The kinetics of appearance of this IgM product provide support for active generation upon stimulation, as opposed to immediate release of a preformed substance. Production of this form of IgM is accompanied by slight elevations in serum levels of IgG1 and normal IgM but unaltered levels of IgG2 and IgA. A molecular weight similar to that of IgG together with the demonstrated presence of light chains suggest that the aberrant product is likely a monomer of IgM. This stimulatory process appears to be thymus dependent because it cannot be induced in congenitally athymic (nude) mice unless they have been thymus reconstituted. Several test protocols involving adult-initiated anti-μ treatment resulted in immune responses to two thymus-dependent complex antigens (rabbit serum and sheep red blood cells) as well as generation of the aberrant IgM product in normal control mice but failed to render nude mice responsive to either antigen. It is thus apparent that although anti-μ antibodies can generate a stimulus in adult mice which results in production of an otherwise undetectable IgM product, the stimulus is not generally interpreted biologically as an immune “signal” complementary to antigen stimulation.

Role of temporary intestinal brush border dysfunction in Campylobacter jejuni diarrhea

The pathophysiologic effects ofCampylobacterjejuni on weanling ferrets were investigated by assessing jejunal disaccharidase activities, glucose and theophylline stimulation of jejunal mucosal ion transport, fecal levels of reducing sugars, and histologic appearance of the gut. Compared with uninoculated controls, ferrets at the peak ofCampylobacter-induced watery diarrhea exhibited two- to threefold reductions in sucrase, maltase, and lactase activity, a sixfold lower short-circuit current response to glucose stimulation, and a twofold higher response to theophylline stimulation, plus a striking increase in fecal levels of reducing sugars. These physiologic alterations rapidly returned to normal as diarrhea subsided. Jejunal epithelial cells of all diarrheic animals appeared morphologically normal by light microscopy. Passively immunized kits, heavily colonized but not diarrheic, were indistinguishable from controls in every assessment. These observations suggest that (i)Campylobacterjejuni exerts its pathophysiologic effect primarily by inducing a transient depression of intestinal brush border function and (ii) such effects can be prevented by humoral antibodies.

Suppression of myeloma establishment in adult mice with anti-μ antiserum

Abstract Uniform suppression of MOPC-104E tumor development was observed in adult BALB/c mice to which 0.4 ml of high titered anti-μ antiserum had been administered intraperitoneally or intravenously one day before subcutaneous tumor implantation. In contrast, when MOPC-104E cells were exposed to anti-μ antiserum in vitro for 10 min and subsequently injected into adult BALB/c mice, inhibition of tumor development was observed in only about half of the subject animals. Nude mice treated intraperitoneally with anti-μ antiserum were also uniformly refractory to MOPC-104E challenge. Anti-μ antiserum exhibited virtually no cytotoxicity against MOPC-104E cells in vitro . These observations suggest that neither complement-mediated cytotoxicity nor T cell-mediated immunity is likely to be the primary mechanism for anti-μ-mediated suppression of myeloma development in adult BALB/c mice. More plausible explanations for this type of suppression include macrophage arming, some type of antibody-dependent cell-mediated cytotoxicity, and/or opsonization.